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See the License for the specific language governing permissions and limitations under the License. ====================================== Flume 1.2.0 User Guide ====================================== Introduction ============ Overview -------- Apache Flume is a distributed, reliable, and available system for efficiently collecting, aggregating and moving large amounts of log data from many different sources to a centralized data store. Apache Flume is a top level project at the Apache Software Foundation. There are currently two release code lines available, versions 0.9.x and 1.x. This documentation applies to the 1.x codeline. Please click here for `the Flume 0.9.x User Guide `_. System Requirements ------------------- TBD Architecture ------------ Data flow model ~~~~~~~~~~~~~~~ A Flume event is defined as a unit of data flow having a byte payload and an optional set of string attributes. A Flume agent is a (JVM) process that hosts the components through which events flow from an external source to the next destination (hop). .. figure:: images/UserGuide_image00.png :align: center :alt: Agent component diagram A Flume source consumes events delivered to it by an external source like a web server. The external source sends events to Flume in a format that is recognized by the target Flume source. For example, an Avro Flume source can be used to receive Avro events from Avro clients or other Flume agents in the flow that send events from an Avro sink. When a Flume source receives an event, it stores it into one or more channels. The channel is a passive store that keeps the event until it's consumed by a Flume sink. The JDBC channel is one example -- it uses a filesystem backed embedded database. The sink removes the event from the channel and puts it into an external repository like HDFS (via Flume HDFS sink) or forwards it to the Flume source of the next Flume agent (next hop) in the flow. The source and sink within the given agent run asynchronously with the events staged in the channel. Complex flows ~~~~~~~~~~~~~ Flume allows a user to build multi-hop flows where events travel through multiple agents before reaching the final destination. It also allows fan-in and fan-out flows, contextual routing and backup routes (fail-over) for failed hops. Reliability ~~~~~~~~~~~ The events are staged in a channel on each agent. The events are then delivered to the next agent or terminal repository (like HDFS) in the flow. The events are removed from a channel only after they are stored in the channel of next agent or in the terminal repository. This is a how the single-hop message delivery semantics in Flume provide end-to-end reliability of the flow. Flume uses a transactional approach to guarantee the reliable delivery of the events. The sources and sinks encapsulate in a transaction the storage/retrieval, respectively, of the events placed in or provided by a transaction provided by the channel. This ensures that the set of events are reliably passed from point to point in the flow. In the case of a multi-hop flow, the sink from the previous hop and the source from the next hop both have their transactions running to ensure that the data is safely stored in the channel of the next hop. Recoverability ~~~~~~~~~~~~~~ The events are staged in the channel, which manages recovery from failure. Flume supports a durable JDBC channel which is backed by a relational database. There's also a memory channel which simply stores the events in an in-memory queue, which is faster but any events still left in the memory channel when an agent process dies can't be recovered. Setup ===== Setting up an agent ------------------- Flume agent configuration is stored in a local configuration file. This is a text file which has a format follows the Java properties file format. Configurations for one or more agents can be specified in the same configuration file. The configuration file includes properties of each source, sink and channel in an agent and how they are wired together to form data flows. Configuring individual components ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Each component (source, sink or channel) in the flow has a name, type, and set of properties that are specific to the type and instantiation. For example, an Avro source needs a hostname (or IP address) and a port number to receive data from. A memory channel can have max queue size ("capacity"), and an HDFS sink needs to know the file system URI, path to create files, frequency of file rotation ("hdfs.rollInterval") etc. All such attributes of a component needs to be set in the properties file of the hosting Flume agent. Wiring the pieces together ~~~~~~~~~~~~~~~~~~~~~~~~~~ The agent needs to know what individual components to load and how they are connected in order to constitute the flow. This is done by listing the names of each of the sources, sinks and channels in the agent, and then specifying the connecting channel for each sink and source. For example, a agent flows events from an Avro source called avroWeb to HDFS sink hdfs-cluster1 via a JDBC channel called jdbc-channel. The configuration file will contain names of these components and jdbc-channel as a shared channel for both avroWeb source and hdfs-cluster1 sink. Starting an agent ~~~~~~~~~~~~~~~~~ An agent is started using a shell script called flume-ng which is located in the bin directory of the Flume distribution. You need to specify the agent name, the config directory, and the config file on the command line:: $ bin/flume-ng agent -n $agent_name -c conf -f conf/flume-conf.properties.template Now the agent will start running source and sinks configured in the given properties file. A simple example ~~~~~~~~~~~~~~~~ Here, we give an example configuration file, describing a single-node Flume deployment. This configuration lets a user generate events and subsequently logs them to the console. .. code-block:: properties # example.conf: A single-node Flume configuration # Name the components on this agent agent1.sources = source1 agent1.sinks = sink1 agent1.channels = channel1 # Describe/configure source1 agent1.sources.source1.type = netcat agent1.sources.source1.bind = localhost agent1.sources.source1.port = 44444 # Describe sink1 agent1.sinks.sink1.type = logger # Use a channel which buffers events in memory agent1.channels.channel1.type = memory agent1.channels.channel1.capacity = 1000 agent1.channels.channel1.transactionCapactiy = 100 # Bind the source and sink to the channel agent1.sources.source1.channels = channel1 agent1.sinks.sink1.channel = channel1 This configuration defines a single agent, called *agent1*. *agent1* has a source that listens for data on port 44444, a channel that buffers event data in memory, and a sink that logs event data to the console. The configuration file names the various components, then describes their types and configuration parameters. A given configuration file might define several named agents; when a given Flume process is launched a flag is passed telling it which named agent to manifest. Given this configuration file, we can start Flume as follows:: $ bin/flume-ng agent --conf-file example.conf --name agent1 -Dflume.root.logger=INFO,console Note that in a full deployment we would typically include one more option: ``--conf=``. The ```` directory would include a shell script *flume-env.sh* and potentially a log4j properties file. In this example, we pass a Java option to force Flume to log to the console and we go without a custom environment script. From a separate terminal, we can then telnet port 44444 and send Flume an event: .. code-block:: properties $ telnet localhost 44444 Trying 127.0.0.1... Connected to localhost.localdomain (127.0.0.1). Escape character is '^]'. Hello world! OK The original Flume terminal will output the event in a log message. .. code-block:: properties 12/06/19 15:32:19 INFO source.NetcatSource: Source starting 12/06/19 15:32:19 INFO source.NetcatSource: Created serverSocket:sun.nio.ch.ServerSocketChannelImpl[/127.0.0.1:44444] 12/06/19 15:32:34 INFO sink.LoggerSink: Event: { headers:{} body: 48 65 6C 6C 6F 20 77 6F 72 6C 64 21 0D Hello world!. } Congratulations - you've successfully configured and deployed a Flume agent! Subsequent sections cover agent configuration in much more detail. Data ingestion -------------- Flume supports a number of mechanisms to ingest data from external sources. RPC ~~~ An Avro client included in the Flume distribution can send a given file to Flume Avro source using avro RPC mechanism:: $ bin/flume-ng avro-client -H localhost -p 41414 -F /usr/logs/log.10 The above command will send the contents of /usr/logs/log.10 to to the Flume source listening on that ports. Executing commands ~~~~~~~~~~~~~~~~~~ There's an exec source that executes a given command and consumes the output. A single 'line' of output ie. text followed by carriage return ('\\r') or line feed ('\\n') or both together. .. note:: Flume does not support tail as a source. One can wrap the tail command in an exec source to stream the file. Network streams ~~~~~~~~~~~~~~~ Flume supports the following mechanisms to read data from popular log stream types, such as: #. Avro #. Syslog #. Netcat Setting multi-agent flow ------------------------ .. figure:: images/UserGuide_image03.png :align: center :alt: Two agents communicating over Avro RPC In order to flow the data across multiple agents or hops, the sink of the previous agent and source of the current hop need to be avro type with the sink pointing to the hostname (or IP address) and port of the source. Consolidation ------------- A very common scenario in log collection is a large number of log producing clients sending data to a few consumer agents that are attached to the storage subsystem. For examples, logs collected from hundreds of web servers sent to a dozen of agents that write to HDFS cluster. .. figure:: images/UserGuide_image02.png :align: center :alt: A fan-in flow using Avro RPC to consolidate events in one place This can be achieved in Flume by configuring a number of first tier agents with an avro sink, all pointing to an avro source of single agent. This source on the second tier agent consolidates the received events into a single channel which is consumed by a sink to its final destination. Multiplexing the flow --------------------- Flume supports multiplexing the event flow to one or more destinations. This is achieved by defining a flow multiplexer that can replicate or selectively route an event to one or more channels. .. figure:: images/UserGuide_image01.png :align: center :alt: A fan-out flow using a (multiplexing) channel selector The above example shows a source from agent "foo" fanning out the flow to three different channels. This fan out can be replicating or multiplexing. In case of replicating flow, each event is sent to all three channels. For the multiplexing case, an event is delivered to a subset of available channels when an event's attribute matches a preconfigured value. For example, if an event attribute called "txnType" is set to "customer", then it should go to channel1 and channel3, if it's "vendor" then it should go to channel2, otherwise channel3. The mapping can be set in the agent's configuration file. Configuration ============= As mentioned in the earlier section, Flume agent configuration is read from a file that resembles a Java property file format with hierarchical property settings. Defining the flow ----------------- To define the flow within a single agent, you need to link the sources and sinks via a channel. You need to list the sources, sinks and channels for the given agent, and then point the source and sink to a channel. A source instance can specify multiple channels, but a sink instance can only specify on channel. The format is as follows: .. code-block:: properties # list the sources, sinks and channels for the agent .sources = .sinks = .channels = # set channel for source .sources..channels = ... # set channel for sink .sinks..channel = For example an agent named agent_foo is reading data from an external avro client and sending it to HDFS via a memory channel. The config file weblog.config could look like: .. code-block:: properties # list the sources, sinks and channels for the agent agent_foo.sources = avro-appserver-src-1 agent_foo.sinks = hdfs-sink-1 agent_foo.channels = mem-channel-1 # set channel for source agent_foo.sources.avro-appserver-src-1.channels = mem-channel-1 # set channel for sink agent_foo.sinks.hdfs-sink-1.channel = mem-channel-1 This will make the events flow from avro-AppSrv-source to hdfs-Cluster1-sink through the memory channel mem-channel-1. When the agent is started with the weblog.config as its config file, it will instantiate that flow. Configuring individual components --------------------------------- After defining the flow, you need to set properties of each source, sink and channel. This is done in the same hierarchical namespace fashion where you set the component type and other values for the properties specific to each component: .. code-block:: properties # properties for sources .sources.. = # properties for channels .channel.. = # properties for sinks .sources.. = The property "type" needs to be set for each component for Flume to understand what kind of object it needs to be. Each source, sink and channel type has its own set of properties required for it to function as intended. All those need to be set as needed. In the previous example, we have a flow from avro-AppSrv-source to hdfs-Cluster1-sink through the memory channel mem-channel-1. Here's an example that shows configuration of each of those components: .. code-block:: properties agent_foo.sources = avro-AppSrv-source agent_foo.sinks = hdfs-Cluster1-sink agent_foo.channels = mem-channel-1 # set channel for sources, sinks # properties of avro-AppSrv-source agent_foo.sources.avro-AppSrv-source.type = avro agent_foo.sources.avro-AppSrv-source.bind = localhost agent_foo.sources.avro-AppSrv-source.port = 10000 # properties of mem-channel-1 agent_foo.channels.mem-channel-1.type = memory agent_foo.channels.mem-channel-1.capacity = 1000 agent_foo.channels.mem-channel-1.transactionCapacity = 100 # properties of hdfs-Cluster1-sink agent_foo.sinks.hdfs-Cluster1-sink.type = hdfs agent_foo.sinks.hdfs-Cluster1-sink.hdfs.path = hdfs://namenode/flume/webdata #... Adding multiple flows in an agent --------------------------------- A single Flume agent can contain several independent flows. You can list multiple sources, sinks and channels in a config. These components can be linked to form multiple flows: .. code-block:: properties # list the sources, sinks and channels for the agent .sources = .sinks = .channels = Then you can link the sources and sinks to their corresponding channels (for sources) of channel (for sinks) to setup two different flows. For example, if you need to setup two flows in an agent, one going from an external avro client to external HDFS and another from output of a tail to avro sink, then here's a config to do that: .. code-block:: properties # list the sources, sinks and channels in the agent agent_foo.sources = avro-AppSrv-source1 exec-tail-source2 agent_foo.sinks = hdfs-Cluster1-sink1 avro-forward-sink2 agent_foo.channels = mem-channel-1 jdbc-channel-2 # flow #1 configuration agent_foo.sources.avro-AppSrv-source1.channels = mem-channel-1 agent_foo.sinks.hdfs-Cluster1-sink1.channel = mem-channel-1 # flow #2 configuration agent_foo.sources.exec-tail-source2.channels = jdbc-channel-2 agent_foo.sinks.avro-forward-sink2.channel = jdbc-channel-2 Configuring a multi agent flow ------------------------------ To setup a multi-tier flow, you need to have an avro sink of first hop pointing to avro source of the next hop. This will result in the first Flume agent forwarding events to the next Flume agent. For example, if you are periodically sending files (1 file per event) using avro client to a local Flume agent, then this local agent can forward it to another agent that has the mounted for storage. Weblog agent config: .. code-block:: properties # list sources, sinks and channels in the agent agent_foo.sources = avro-AppSrv-source agent_foo.sinks = avro-forward-sink agent_foo.channels = jdbc-channel # define the flow agent_foo.sources.avro-AppSrv-source.channels = jdbc-channel agent_foo.sinks.avro-forward-sink.channel = jdbc-channel # avro sink properties agent_foo.sources.avro-forward-sink.type = avro agent_foo.sources.avro-forward-sink.hostname = 10.1.1.100 agent_foo.sources.avro-forward-sink.port = 10000 # configure other pieces #... HDFS agent config: .. code-block:: properties # list sources, sinks and channels in the agent agent_foo.sources = avro-collection-source agent_foo.sinks = hdfs-sink agent_foo.channels = mem-channel # define the flow agent_foo.sources.avro-collection-source.channels = mem-channel agent_foo.sinks.hdfs-sink.channel = mem-channel # avro sink properties agent_foo.sources.avro-collection-source.type = avro agent_foo.sources.avro-collection-source.bind = 10.1.1.100 agent_foo.sources.avro-collection-source.port = 10000 # configure other pieces #... Here we link the avro-forward-sink from the weblog agent to the avro-collection-source of the hdfs agent. This will result in the events coming from the external appserver source eventually getting stored in HDFS. Fan out flow ------------ As discussed in previous section, Flume support fanning out the flow from one source to multiple channels. There are two modes of fan out, replicating and multiplexing. In the replicating flow the event is sent to all the configured channels. In case of multiplexing, the event is sent to only a subset of qualifying channels. To fan out the flow, one needs to specify a list of channels for a source and the policy for the fanning it out. This is done by adding a channel "selector" that can be replicating or multiplexing. Then further specify the selection rules if it's a multiplexer. If you don't specify an selector, then by default it's replicating: .. code-block:: properties # List the sources, sinks and channels for the agent .sources = .sinks = .channels = # set list of channels for source (separated by space) .sources..channels = # set channel for sinks .sinks..channel = .sinks..channel = .sources..selector.type = replicating The multiplexing select has a further set of properties to bifurcate the flow. This requires specifying a mapping of an event attribute to a set for channel. The selector checks for each configured attribute in the event header. If it matches the specified value, then that event is sent to all the channels mapped to that value. If there's no match, then the event is sent to set of channels configured as default: .. code-block:: properties # Mapping for multiplexing selector .sources..selector.type = multiplexing .sources..selector.header = .sources..selector.mapping. = .sources..selector.mapping. = .sources..selector.mapping. = #... .sources..selector.default = The mapping allows overlapping the channels for each value. The default must be set for a multiplexing select which can also contain any number of channels. The following example has a single flow that multiplexed to two paths. The agent named agent_foo has a single avro source and two channels linked to two sinks: .. code-block:: properties # list the sources, sinks and channels in the agent agent_foo.sources = avro-AppSrv-source1 agent_foo.sinks = hdfs-Cluster1-sink1 avro-forward-sink2 agent_foo.channels = mem-channel-1 jdbc-channel-2 # set channels for source agent_foo.sources.avro-AppSrv-source1.channels = mem-channel-1 jdbc-channel-2 # set channel for sinks agent_foo.sinks.hdfs-Cluster1-sink1.channel = mem-channel-1 agent_foo.sinks.avro-forward-sink2.channel = jdbc-channel-2 # channel selector configuration agent_foo.sources.avro-AppSrv-source1.selector.type = multiplexing agent_foo.sources.avro-AppSrv-source1.selector.header = State agent_foo.sources.avro-AppSrv-source1.selector.mapping.CA = mem-channel-1 agent_foo.sources.avro-AppSrv-source1.selector.mapping.AZ = jdbc-channel-2 agent_foo.sources.avro-AppSrv-source1.selector.mapping.NY = mem-channel-1 jdbc-channel-2 agent_foo.sources.avro-AppSrv-source1.selector.default = mem-channel-1 The selector checks for a header called "State". If the value is "CA" then its sent to mem-channel-1, if its "AZ" then it goes to jdbc-channel-2 or if its "NY" then both. If the "State" header is not set or doesn't match any of the three, then it goes to mem-channel-1 which is designated as 'default'. Flume Sources ------------- Avro Source ~~~~~~~~~~~ Listens on Avro port and receives events from external Avro client streams. When paired with the built-in AvroSink on another (previous hop) Flume agent, it can create tiered collection topologies. Required properties are in **bold**. ============== =========== =================================================== Property Name Default Description ============== =========== =================================================== **channels** -- **type** -- The component type name, needs to be ``avro`` **bind** -- hostname or IP address to listen on **port** -- Port # to bind to threads -- Maximum number of worker threads to spawn interceptors -- Space separated list of interceptors interceptors.* ============== =========== =================================================== Example for agent named **agent_foo**: .. code-block:: properties agent_foo.sources = avrosource-1 agent_foo.channels = memoryChannel-1 agent_foo.sources.avrosource-1.type = avro agent_foo.sources.avrosource-1.channels = memoryChannel-1 agent_foo.sources.avrosource-1.bind = 0.0.0.0 agent_foo.sources.avrosource-1.port = 4141 Exec Source ~~~~~~~~~~~ Exec source runs a given Unix command on start-up and expects that process to continuously produce data on standard out (stderr is simply discarded, unless property logStdErr is set to true). If the process exits for any reason, the source also exits and will produce no further data. This means configurations such as ``cat [named pipe]`` or ``tail -F [file]`` are going to produce the desired results where as ``date`` will probably not - the former two commands produce streams of data where as the latter produces a single event and exits. Required properties are in **bold**. =============== =========== ============================================================== Property Name Default Description =============== =========== ============================================================== **channels** -- **type** -- The component type name, needs to be ``exec`` **command** -- The command to execute restartThrottle 10000 Amount of time (in millis) to wait before attempting a restart restart false Whether the executed cmd should be restarted if it dies logStdErr false Whether the command's stderr should be logged selector.type replicating replicating or multiplexing selector.* Depends on the selector.type value interceptors -- Space separated list of interceptors interceptors.* =============== =========== ============================================================== .. warning:: The problem with ExecSource and other asynchronous sources is that the source can not guarantee that if there is a failure to put the event into the Channel the client knows about it. In such cases, the data will be lost. As a for instance, one of the most commonly requested features is the ``tail -F [file]``-like use case where an application writes to a log file on disk and Flume tails the file, sending each line as an event. While this is possible, there's an obvious problem; what happens if the channel fills up and Flume can't send an event? Flume has no way of indicating to the application writing the log file that it needs to retain the log or that the event hasn't been sent, for some reason. If this doesn't make sense, you need only know this: Your application can never guarantee data has been received when using a unidirectional asynchronous interface such as ExecSource! As an extension of this warning - and to be completely clear - there is absolutely zero guarantee of event delivery when using this source. You have been warned. .. note:: You can use ExecSource to emulate TailSource from Flume 0.9x (flume og). Just use unix command ``tail -F /full/path/to/your/file``. Parameter -F is better in this case than -f as it will also follow file rotation. Example for agent named **agent_foo**: .. code-block:: properties agent_foo.sources = tailsource-1 agent_foo.channels = memoryChannel-1 agent_foo.sources.tailsource-1.type = exec agent_foo.sources.tailsource-1.command = tail -F /var/log/secure agent_foo.sources.tailsource-1.channels = memoryChannel-1 NetCat Source ~~~~~~~~~~~~~ A netcat-like source that listens on a given port and turns each line of text into an event. Acts like ``nc -k -l [host] [port]``. In other words, it opens a specified port and listens for data. The expectation is that the supplied data is newline separated text. Each line of text is turned into a Flume event and sent via the connected channel. Required properties are in **bold**. =============== =========== =========================================== Property Name Default Description =============== =========== =========================================== **channels** -- **type** -- The component type name, needs to be ``netcat`` **bind** -- Host name or IP address to bind to **port** -- Port # to bind to max-line-length 512 Max line length per event body (in bytes) selector.type replicating replicating or multiplexing selector.* Depends on the selector.type value interceptors -- Space separated list of interceptors interceptors.* =============== =========== =========================================== Example for agent named **agent_foo**: .. code-block:: properties agent_foo.sources = ncsource-1 agent_foo.channels = memoryChannel-1 agent_foo.sources.ncsource-1.type = netcat agent_foo.sources.ncsource-1.bind = 0.0.0.0 agent_foo.sources.ncsource-1.bind = 6666 agent_foo.sources.ncsource-1.channels = memoryChannel-1 Sequence Generator Source ~~~~~~~~~~~~~~~~~~~~~~~~~ A simple sequence generator that continuously generates events with a counter that starts from 0 and increments by 1. Useful mainly for testing. Required properties are in **bold**. ============== =========== ======================================== Property Name Default Description ============== =========== ======================================== **channels** -- **type** -- The component type name, needs to be ``seq`` selector.type replicating or multiplexing selector.* replicating Depends on the selector.type value interceptors -- Space separated list of interceptors interceptors.* ============== =========== ======================================== Example for agent named **agent_foo**: .. code-block:: properties agent_foo.sources = ncsource-1 agent_foo.channels = memoryChannel-1 agent_foo.sources.ncsource-1.type = seq agent_foo.sources.ncsource-1.channels = memoryChannel-1 Syslog Sources ~~~~~~~~~~~~~~ Reads syslog data and generate Flume events. The UDP source treats an entire message as a single event. The TCP source on creates a new event for a string of characters separated by carriage return ('\n'). Required properties are in **bold**. Syslog TCP Source ''''''''''''''''' ============== =========== ============================================== Property Name Default Description ============== =========== ============================================== **channels** -- **type** -- The component type name, needs to be ``syslogtcp`` **host** -- Host name or IP address to bind to **port** -- Port # to bind to eventSize 2500 selector.type replicating or multiplexing selector.* replicating Depends on the selector.type value interceptors -- Space separated list of interceptors interceptors.* ============== =========== ============================================== For example, a syslog TCP source for agent named **agent_foo**: .. code-block:: properties agent_foo.sources = syslogsource-1 agent_foo.channels = memoryChannel-1 agent_foo.sources.syslogsource-1.type = syslogtcp agent_foo.sources.syslogsource-1.port = 5140 agent_foo.sources.syslogsource-1.host = localhost agent_foo.sources.syslogsource-1.channels = memoryChannel-1 Syslog UDP Source ''''''''''''''''' ============== =========== ============================================== Property Name Default Description ============== =========== ============================================== **channels** -- **type** -- The component type name, needs to be ``syslogudp`` **host** -- Host name or IP address to bind to **port** -- Port # to bind to selector.type replicating or multiplexing selector.* replicating Depends on the selector.type value interceptors -- Space separated list of interceptors interceptors.* ============== =========== ============================================== For example, a syslog UDP source for agent named **agent_foo**: .. code-block:: properties agent_foo.sources = syslogsource-1 agent_foo.channels = memoryChannel-1 agent_foo.sources.syslogsource-1.type = syslogudp agent_foo.sources.syslogsource-1.port = 5140 agent_foo.sources.syslogsource-1.host = localhost agent_foo.sources.syslogsource-1.channels = memoryChannel-1 Legacy Sources ~~~~~~~~~~~~~~ The legacy sources allow a Flume 1.x agent to receive events from Flume 0.9.4 agents. It accepts events in the Flume 0.9.4 format, converts them to the Flume 1.0 format, and stores them in the connected channel. The 0.9.4 event properties like timestamp, pri, host, nanos, etc get converted to 1.x event header attributes. The legacy source supports both Avro and Thrift RPC connections. To use this bridge between two Flume versions, you need to start a Flume 1.x agent with the avroLegacy or thriftLegacy source. The 0.9.4 agent should have the agent Sink pointing to the host/port of the 1.x agent. .. note:: The reliability semantics of Flume 1.x are different from that of Flume 0.9.x. The E2E or DFO mode of a Flume 0.9.x agent will not be supported by the legacy source. The only supported 0.9.x mode is the best effort, though the reliability setting of the 1.x flow will be applicable to the events once they are saved into the Flume 1.x channel by the legacy source. Required properties are in **bold**. Avro Legacy Source '''''''''''''''''' ============== =========== ======================================================================================== Property Name Default Description ============== =========== ======================================================================================== **channels** -- **type** -- The component type name, needs to be ``org.apache.flume.source.avroLegacy.AvroLegacySource`` **host** -- The hostname or IP address to bind to **port** -- The port # to listen on selector.type replicating or multiplexing selector.* replicating Depends on the selector.type value interceptors -- Space separated list of interceptors interceptors.* ============== =========== ======================================================================================== Example for agent named **agent_foo**: .. code-block:: properties agent_foo.sources = legacysource-1 agent_foo.channels = memoryChannel-1 agent_foo.sources.legacysource-1.type = org.apache.flume.source.avroLegacy.AvroLegacySource agent_foo.sources.legacysource-1.host = 0.0.0.0 agent_foo.sources.legacysource-1.bind = 6666 agent_foo.sources.legacysource-1.channels = memoryChannel-1 Thrift Legacy Source '''''''''''''''''''' ============== =========== ====================================================================================== Property Name Default Description ============== =========== ====================================================================================== **channels** -- **type** -- The component type name, needs to be ``org.apache.source.thriftLegacy.ThriftLegacySource`` **host** -- The hostname or IP address to bind to **port** -- The port # to listen on selector.type replicating or multiplexing selector.* replicating Depends on the selector.type value interceptors -- Space separated list of interceptors interceptors.* ============== =========== ====================================================================================== Example for agent named **agent_foo**: .. code-block:: properties agent_foo.sources = legacysource-1 agent_foo.channels = memoryChannel-1 agent_foo.sources.legacysource-1.type = org.apache.source.thriftLegacy.ThriftLegacySource agent_foo.sources.legacysource-1.host = 0.0.0.0 agent_foo.sources.legacysource-1.bind = 6666 agent_foo.sources.legacysource-1.channels = memoryChannel-1 Custom Source ~~~~~~~~~~~~~ A custom source is your own implementation of the Source interface. A custom source's class and its dependencies must be included in the agent's classpath when starting the Flume agent. The type of the custom source is its FQCN. ============== =========== ============================================== Property Name Default Description ============== =========== ============================================== **channels** -- **type** -- The component type name, needs to be your FQCN selector.type replicating or multiplexing selector.* replicating Depends on the selector.type value interceptors -- Space separated list of interceptors interceptors.* ============== =========== ============================================== Example for agent named **agent_foo**: .. code-block:: properties agent_foo.sources = legacysource-1 agent_foo.channels = memoryChannel-1 agent_foo.sources.legacysource-1.type = your.namespace.YourClass agent_foo.sources.legacysource-1.channels = memoryChannel-1 Flume Sinks ----------- HDFS Sink ~~~~~~~~~ This sink writes events into the Hadoop Distributed File System (HDFS). It currently supports creating text and sequence files. It supports compression in both file types. The files can be rolled (close current file and create a new one) periodically based on the elapsed time or size of data or number of events. It also buckets/partitions data by attributes like timestamp or machine where the event originated. The HDFS directory path may contain formatting escape sequences that will replaced by the HDFS sink to generate a directory/file name to store the events. Using this sink requires hadoop to be installed so that Flume can use the Hadoop jars to communicate with the HDFS cluster. Note that a version of Hadoop that supports the sync() call is required. The following are the escape sequences supported: ========= ================================================= Alias Description ========= ================================================= %{host} Substitute value of event header named "host". Arbitrary header names are supported. %t Unix time in milliseconds %a locale's short weekday name (Mon, Tue, ...) %A locale's full weekday name (Monday, Tuesday, ...) %b locale's short month name (Jan, Feb, ...) %B locale's long month name (January, February, ...) %c locale's date and time (Thu Mar 3 23:05:25 2005) %d day of month (01) %D date; same as %m/%d/%y %H hour (00..23) %I hour (01..12) %j day of year (001..366) %k hour ( 0..23) %m month (01..12) %M minute (00..59) %p locale's equivalent of am or pm %s seconds since 1970-01-01 00:00:00 UTC %S second (00..59) %y last two digits of year (00..99) %Y year (2010) %z +hhmm numeric timezone (for example, -0400) ========= ================================================= The file in use will have the name mangled to include ".tmp" at the end. Once the file is closed, this extension is removed. This allows excluding partially complete files in the directory. Required properties are in **bold**. ====================== ============ ====================================================================== Name Default Description ====================== ============ ====================================================================== **channel** -- **type** -- The component type name, needs to be ``hdfs`` **hdfs.path** -- HDFS directory path (eg hdfs://namenode/flume/webdata/) hdfs.filePrefix FlumeData Name prefixed to files created by Flume in hdfs directory hdfs.rollInterval 30 Number of seconds to wait before rolling current file (0 = never roll based on time interval) hdfs.rollSize 1024 File size to trigger roll, in bytes (0: never roll based on file size) hdfs.rollCount 10 Number of events written to file before it rolled (0 = never roll based on number of events) hdfs.batchSize 1 number of events written to file before it flushed to HDFS hdfs.txnEventMax 100 hdfs.codeC -- Compression codec. one of following : gzip, bzip2, lzo, snappy hdfs.fileType SequenceFile File format: currently ``SequenceFile``, ``DataStream`` or ``CompressedStream`` (1)DataStream will not compress output file and please don't set codeC (2)CompressedStream requires set hdfs.codeC with an available codeC hdfs.maxOpenFiles 5000 hdfs.writeFormat -- "Text" or "Writable" hdfs.appendTimeout 1000 hdfs.callTimeout 10000 hdfs.threadsPoolSize 10 Number of threads per HDFS sink for HDFS IO ops (open, write, etc.) hdfs.rollTimerPoolSize 1 Number of threads per HDFS sink for scheduling timed file rolling hdfs.kerberosPrincipal -- Kerberos user principal for accessing secure HDFS hdfs.kerberosKeytab -- Kerberos keytab for accessing secure HDFS hdfs.round false Should the timestamp be rounded down (if true, affects all time based escape sequences except %t) hdfs.roundValue 1 Rounded down to the highest multiple of this (in the unit configured using ``hdfs.roundUnit``), less than current time. hdfs.roundUnit second The unit of the round down value - ``second``, ``minute`` or ``hour``. serializer ``TEXT`` Other possible options include ``AVRO_EVENT`` or the fully-qualified class name of an implementation of the ``EventSerializer.Builder`` interface. serializer.* ====================== ============ ====================================================================== Example for agent named **agent_foo**: .. code-block:: properties agent_foo.channels = memoryChannel-1 agent_foo.sinks = hdfsSink-1 agent_foo.sinks.hdfsSink-1.type = hdfs agent_foo.sinks.hdfsSink-1.channels = memoryChannel-1 agent_foo.sinks.hdfsSink-1.hdfs.path = /flume/events/%y-%m-%d/%H%M/%S agent_foo.sinks.hdfsSink-1.hdfs.filePrefix = events- agent_foo.sinks.hdfsSink-1.hdfs.round = true agent_foo.sinks.hdfsSink-1.hdfs.roundValue = 10 agent_foo.sinks.hdfsSink-1.hdfs.roundUnit = minute The above configuration will round down the timestamp to the last 10th minute. For example, an event with timestamp 11:54:34 AM, June 12, 2012 will cause the hdfs path to become ``/flume/events/2012-06-12/1150/00``. Logger Sink ~~~~~~~~~~~ Logs event at INFO level. Typically useful for testing/debugging purpose. Required properties are in **bold**. ============== ======= =========================================== Property Name Default Description ============== ======= =========================================== **channel** -- **type** -- The component type name, needs to be ``logger`` ============== ======= =========================================== Example for agent named **agent_foo**: .. code-block:: properties agent_foo.channels = memoryChannel-1 agent_foo.sinks = loggerSink-1 agent_foo.sinks.loggerSink-1.type = logger agent_foo.sinks.loggerSink-1.channels = memoryChannel-1 Avro Sink ~~~~~~~~~ This sink forms one half of Flume's tiered collection support. Flume events sent to this sink are turned into Avro events and sent to the configured hostname / port pair. The events are taken from the configured Channel in batches of the configured batch size. Required properties are in **bold**. =============== ======= ============================================== Property Name Default Description =============== ======= ============================================== **channel** -- **type** -- The component type name, needs to be ``avro``. **hostname** -- The hostname or IP address to bind to. **port** -- The port # to listen on. batch-size 100 number of event to batch together for send. connect-timeout 20000 Amount of time (ms) to allow for the first (handshake) request. request-timeout 20000 Amount of time (ms) to allow for requests after the first. =============== ======= ============================================== Example for agent named **agent_foo**: .. code-block:: properties agent_foo.channels = memoryChannel-1 agent_foo.sinks = avroSink-1 agent_foo.sinks.avroSink-1.type = avro agent_foo.sinks.avroSink-1.channels = memoryChannel-1 agent_foo.sinks.avroSink-1.hostname = 10.10.10.10 agent_foo.sinks.avroSink-1.port = 4545 IRC Sink ~~~~~~~~ The IRC sink takes messages from attached channel and relays those to configured IRC destinations. Required properties are in **bold**. =============== ======= ======================================================== Property Name Default Description =============== ======= ======================================================== **channel** -- **type** -- The component type name, needs to be ``irc`` **hostname** -- The hostname or IP address to connect to port 6667 The port number of remote host to connect **nick** -- Nick name user -- User name password -- User password **chan** -- channel name splitlines -- (boolean) splitchars \n line separator (if you were to enter the default value into the config file, then you would need to escape the backslash, like this: "\\n") =============== ======= ======================================================== Example for agent named **agent_foo**: .. code-block:: properties agent_foo.channels = memoryChannel-1 agent_foo.sinks = ircSink-1 agent_foo.sinks.ircSink-1.type = irc agent_foo.sinks.ircSink-1.channels = memoryChannel-1 agent_foo.sinks.ircSink-1.hostname = irc.yourdomain.com agent_foo.sinks.ircSink-1.nick = flume agent_foo.sinks.ircSink-1.chan = #flume File Roll Sink ~~~~~~~~~~~~~~ Stores events on the local filesystem. Required properties are in **bold**. ================= ======= ====================================================================================================================== Property Name Default Description ================= ======= ====================================================================================================================== **channel** -- **type** -- The component type name, needs to be ``FILE_ROLL``. sink.directory -- sink.rollInterval 30 Roll the file every 30 seconds. Specifying 0 will disable rolling and cause all events to be written to a single file. sink.serializer TEXT Other possible options include AVRO_EVENT or the FQCN of an implementation of EventSerializer.Builder interface. ================= ======= ====================================================================================================================== Example for agent named **agent_foo**: .. code-block:: properties agent_foo.channels = memoryChannel-1 agent_foo.sinks = fileSink-1 agent_foo.sinks.fileSink-1.type = FILE_ROLL agent_foo.sinks.fileSink-1.channels = memoryChannel-1 agent_foo.sinks.fileSink-1.sink.directory = /var/log/flume Null Sink ~~~~~~~~~ Discards all events it receives from the channel. Required properties are in **bold**. ============= ======= ============================================== Property Name Default Description ============= ======= ============================================== **channel** -- **type** -- The component type name, needs to be ``NULL``. ============= ======= ============================================== Example for agent named **agent_foo**: .. code-block:: properties agent_foo.channels = memoryChannel-1 agent_foo.sinks = nullSink-1 agent_foo.sinks.nullSink-1.type = NULL agent_foo.sinks.nullSink-1.channels = memoryChannel-1 HBaseSinks ~~~~~~~~~~ HBaseSink ''''''''' This sink writes data to HBase. The Hbase configuration is picked up from the first hbase-site.xml encountered in the classpath. A class implementing HbaseEventSerializer which is specified by the configuration is used to convert the events into HBase puts and/or increments. These puts and increments are then written to HBase. This sink provides the same consistency guarantees as HBase, which is currently row-wise atomicity. In the event of Hbase failing to write certain events, the sink will replay all events in that transaction. For convenience two serializers are provided with flume. The SimpleHbaseEventSerializer (org.apache.flume.sink.hbase.SimpleHbaseEventSerializer) writes the event body as is to HBase, and optionally increments a column in Hbase. This is primarily an example implementation. The RegexHbaseEventSerializer (org.apache.flume.sink.hbase.RegexHbaseEventSerializer) breaks the event body based on the given regex and writes each part into different columns. The type is the FQCN: org.apache.flume.sink.hbase.HBaseSink. Required properties are in **bold**. ================ ====================================================== ======================================================================== Property Name Default Description ================ ====================================================== ======================================================================== **channel** -- **type** -- The component type name, needs to be ``org.apache.flume.sink.HBaseSink`` **table** -- The name of the table in Hbase to write to. **columnFamily** -- The column family in Hbase to write to. batchSize 100 Number of events to be written per txn. serializer org.apache.flume.sink.hbase.SimpleHbaseEventSerializer serializer.* -- Properties to be passed to the serializer. ================ ====================================================== ======================================================================== Example for agent named **agent_foo**: .. code-block:: properties agent_foo.channels = memoryChannel-1 agent_foo.sinks = hbaseSink-1 agent_foo.sinks.hbaseSink-1.type = org.apache.flume.sink.hbase.HBaseSink agent_foo.sinks.hbaseSink-1.table = foo_table agent_foo.sinks.hbaseSink-1.columnFamily = bar_cf agent_foo.sinks.hbaseSink-1.serializer = org.apache.flume.sink.hbase.RegexHbaseEventSerializer agent_foo.sinks.hbaseSink-1.channels = memoryChannel-1 AsyncHBaseSink '''''''''''''' This sink writes data to HBase using an asynchronous model. A class implementing AsyncHbaseEventSerializer which is specified by the configuration is used to convert the events into HBase puts and/or increments. These puts and increments are then written to HBase. This sink provides the same consistency guarantees as HBase, which is currently row-wise atomicity. In the event of Hbase failing to write certain events, the sink will replay all events in that transaction. This sink is still experimental. The type is the FQCN: org.apache.flume.sink.hbase.AsyncHBaseSink. Required properties are in **bold**. ================ ============================================================ ============================================================================= Property Name Default Description ================ ============================================================ ============================================================================= **channel** -- **type** -- The component type name, needs to be ``org.apache.flume.sink.AsyncHBaseSink`` **table** -- The name of the table in Hbase to write to. **columnFamily** -- The column family in Hbase to write to. batchSize 100 Number of events to be written per txn. serializer org.apache.flume.sink.hbase.SimpleAsyncHbaseEventSerializer serializer.* -- Properties to be passed to the serializer. ================ ============================================================ ============================================================================= Example for agent named **agent_foo**: .. code-block:: properties agent_foo.channels = memoryChannel-1 agent_foo.sinks = hbaseSink-1 agent_foo.sinks.hbaseSink-1.type = org.apache.flume.sink.hbase.AsyncHBaseSink agent_foo.sinks.hbaseSink-1.table = foo_table agent_foo.sinks.hbaseSink-1.columnFamily = bar_cf agent_foo.sinks.hbaseSink-1.serializer = org.apache.flume.sink.hbase.SimpleAsyncHbaseEventSerializer agent_foo.sinks.hbaseSink-1.channels = memoryChannel-1 Custom Sink ~~~~~~~~~~~ A custom sink is your own implementation of the Sink interface. A custom sink's class and its dependencies must be included in the agent's classpath when starting the Flume agent. The type of the custom sink is its FQCN. Required properties are in **bold**. ============= ======= ============================================== Property Name Default Description ============= ======= ============================================== **channel** -- **type** -- The component type name, needs to be your FQCN ============= ======= ============================================== Example for agent named **agent_foo**: .. code-block:: properties agent_foo.channels = memoryChannel-1 agent_foo.sinks = customSink-1 agent_foo.sinks.customSink-1.type = your.namespace.YourClass agent_foo.sinks.customSink-1.channels = memoryChannel-1 Flume Channels -------------- Channels are the repositories where the events are staged on a agent. Source adds the events and Sink removes it. Memory Channel ~~~~~~~~~~~~~~ The events are stored in a an in-memory queue with configurable max size. It's ideal for flow that needs higher throughput and prepared to lose the staged data in the event of a agent failures. Required properties are in **bold**. =================== ======= ============================================================== Property Name Default Description =================== ======= ============================================================== **type** -- The component type name, needs to be ``memory`` capacity 100 The max number of events stored in the channel transactionCapacity 100 The max number of events stored in the channel per transaction keep-alive 3 Timeout in seconds for adding or removing an event =================== ======= ============================================================== Example for agent named **agent_foo**: .. code-block:: properties agent_foo.channels = memoryChannel-1 agent_foo.channels.memoryChannel-1.type = memory agent_foo.channels.memoryChannel-1.capacity = 1000 JDBC Channel ~~~~~~~~~~~~ The events are stored in a persistent storage that's backed by a database. The JDBC channel currently supports embedded Derby. This is a durable channel that's ideal for the flows where recoverability is important. Required properties are in **bold**. ========================== ==================================== ================================================= Property Name Default Description ========================== ==================================== ================================================= **type** -- The component type name, needs to be ``jdbc`` db.type DERBY Database vendor, needs to be DERBY. driver.class org.apache.derby.jdbc.EmbeddedDriver Class for vendor's JDBC driver driver.url (constructed from other properties) JDBC connection URL db.username "sa" User id for db connection db.password -- password for db connection connection.properties.file -- JDBC Connection property file path create.schema true If true, then creates db schema if not there create.index true Create indexes to speed up lookups create.foreignkey true transaction.isolation "READ_COMMITTED" Isolation level for db session READ_UNCOMMITTED, READ_COMMITTED, SERIALIZABLE, REPEATABLE_READ maximum.connections 10 Max connections allowed to db maximum.capacity 0 (unlimited) Max number of events in the channel sysprop.* DB Vendor specific properties sysprop.user.home Home path to store embedded Derby database ========================== ==================================== ================================================= Example for agent named **agent_foo**: .. code-block:: properties agent_foo.channels = jdbcChannel-1 agent_foo.channels.jdbcChannel-1.type = jdbc Recoverable Memory Channel ~~~~~~~~~~~~~~~~~~~~~~~~~~ .. warning:: The Recoverable Memory Channel is currently experimental and is not yet ready for production use. This channel's properties are being documented here in advance of its completion. Required properties are in **bold**. ====================== =============================================== ========================================================================= Property Name Default Description ====================== =============================================== ========================================================================= **type** -- The component type name, needs to be ``org.apache.flume.channel.recoverable.memory.RecoverableMemoryChannel`` wal.dataDir ${user.home}/.flume/recoverable-memory-channel wal.rollSize (0x04000000) Max size (in bytes) of a single file before we roll wal.minRetentionPeriod 300000 Min amount of time (in millis) to keep a log wal.workerInterval 60000 How often (in millis) the background worker checks for old logs wal.maxLogsSize (0x20000000) Total amt (in bytes) of logs to keep, excluding the current log ====================== =============================================== ========================================================================= File Channel ~~~~~~~~~~~~ Required properties are in **bold**. ==================== ================================ ======================================================== Property Name Default Description ==================== ================================ ======================================================== **type** -- The component type name, needs to be ``FILE``. checkpointDir ~/.flume/file-channel/checkpoint The directory where checkpoint file will be stored dataDirs ~/.flume/file-channel/data The directory where log files will be stored transactionCapacity 1000 The maximum size of transaction supported by the channel checkpointInterval 30000 Amount of time (in millis) between checkpoints maxFileSize 2146435071 Max size (in bytes) of a single log file capacity 1000000 Maximum capacity of the channel keep-alive 3 Amount of time (in sec) to wait for a put operation write-timeout 3 Amount of time (in sec) to wait for a write operation ==================== ================================ ======================================================== .. note:: By default the File Channel uses paths for checkpoint and data directories that are within the user home as specified above. As a result if you have more than one File Channel instances active within the agent, only one will be able to lock the directories and cause the other channel initialization to fail. It is therefore necessary that you provide explicit paths to all the configured channels, preferably on different disks. Example for agent named **agent_foo**: .. code-block:: properties agent_foo.channels = fileChannel-1 agent_foo.channels.fileChannel-1.type = file agent_foo.channels.fileChannel-1.checkpointDir = /mnt/flume/checkpoint agent_foo.channels.fileChannel-1.dataDirs = /mnt/flume/data Pseudo Transaction Channel ~~~~~~~~~~~~~~~~~~~~~~~~~~ .. warning:: The Pseudo Transaction Channel is only for unit testing purposes and is NOT meant for production use. Required properties are in **bold**. ============= ======= ==================================================================================== Property Name Default Description ============= ======= ==================================================================================== **type** -- The component type name, needs to be ``org.apache.flume.channel.PseudoTxnMemoryChannel`` capacity 50 The max number of events stored in the channel keep-alive 3 Timeout in seconds for adding or removing an event ============= ======= ==================================================================================== Custom Channel ~~~~~~~~~~~~~~ A custom channel is your own implementation of the Channel interface. A custom channel's class and its dependencies must be included in the agent's classpath when starting the Flume agent. The type of the custom channel is its FQCN. Required properties are in **bold**. ============= ======= ================================================================= Property Name Default Description ============= ======= ================================================================= **type** -- The component type name, needs to be a fully-qualified class name ============= ======= ================================================================= Example for agent named **agent_foo**: .. code-block:: properties agent_foo.channels = customChannel-1 agent_foo.channels.customChannel-1.type = your.domain.YourClass Flume Channel Selectors ----------------------- If the type is not specified, then defaults to "replicating". Replicating Channel Selector (default) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Required properties are in **bold**. ============= =========== ================================================ Property Name Default Description ============= =========== ================================================ selector.type replicating The component type name, needs to be ``replicating`` ============= =========== ================================================ Example for agent named **agent_foo** and it's source called **source_foo**: .. code-block:: properties agent_foo.sources = source_foo agent_foo.channels = channel-1 channel-2 channel-3 agent_foo.source.source_foo.selector.type = replicating agent_foo.source.source_foo.channels = channel-1 channel-2 channel-3 Multiplexing Channel Selector ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Required properties are in **bold**. ================== ===================== ================================================= Property Name Default Description ================== ===================== ================================================= selector.type replicating The component type name, needs to be ``multiplexing`` selector.header flume.selector.header selector.default -- selector.mapping.* -- ================== ===================== ================================================= Example for agent named **agent_foo** and it's source called **source_foo**: .. code-block:: properties agent_foo.sources = source_foo agent_foo.channels = channel-1 channel-2 channel-3 channel-4 agent_foo.sources.source_foo.selector.type = multiplexing agent_foo.sources.source_foo.selector.header = state agent_foo.sources.source_foo.selector.mapping.CZ = channel-1 agent_foo.sources.source_foo.selector.mapping.US = channel-2 channel-3 agent_foo.sources.source_foo.selector.default = channel-4 Custom Channel Selector ~~~~~~~~~~~~~~~~~~~~~~~ A custom channel selector is your own implementation of the ChannelSelector interface. A custom channel selector's class and its dependencies must be included in the agent's classpath when starting the Flume agent. The type of the custom channel selector is its FQCN. ============= ======= ============================================== Property Name Default Description ============= ======= ============================================== selector.type -- The component type name, needs to be your FQCN ============= ======= ============================================== Example for agent named **agent_foo** and it's source called **source_foo**: .. code-block:: properties agent_foo.sources = source_foo agent_foo.channels = channel-1 agent_foo.sources.source_foo.selector.type = your.namespace.YourClass Flume Sink Processors --------------------- Sink groups allow users to group multiple sinks into one entity. Sink processors can be used to provide load balancing capabilities over all sinks inside the group or to achieve fail over from one sink to another in case of temporal failure. Required properties are in **bold**. =================== =========== ================================================================================= Property Name Default Description =================== =========== ================================================================================= **processor.sinks** -- Space separated list of sinks that are participating in the group **processor.type** ``default`` The component type name, needs to be ``default``, ``failover`` or ``load_balance`` =================== =========== ================================================================================= Example for agent named **agent_foo**: .. code-block:: properties agent_foo.sinkgroups = group1 agent_foo.sinkgroups.group1.sinks = sink1 sink2 agent_foo.sinkgroups.group1.processor.type = load_balance Default Sink Processor ~~~~~~~~~~~~~~~~~~~~~~ Default sink processor accepts only a single sink. User is not forced to create processor (sink group) for single sinks. Instead user can follow the source - channel - sink pattern that was explained above in this user guide. Failover Sink Processor ~~~~~~~~~~~~~~~~~~~~~~~ Failover Sink Processor maintains a prioritized list of sinks, guaranteeing that so long as one is available events will be processed (delivered). The fail over mechanism works by relegating failed sinks to a pool where they are assigned a cool down period, increasing with sequential failures before they are retried. Once a sink successfully sends an event it is restored to the live pool. To configure, set a sink groups processor to ``failover`` and set priorities for all individual sinks. All specified priorities must be unique. Furthermore, upper limit to fail over time can be set (in milliseconds) using ``maxpenalty`` property. Required properties are in **bold**. ================================= =========== =================================================================================== Property Name Default Description ================================= =========== =================================================================================== **processor.sinks** -- Space separated list of sinks that are participating in the group **processor.type** ``default`` The component type name, needs to be ``failover`` **processor.priority.** -- must be one of the sink instances associated with the current sink group processor.maxpenalty 30000 (in millis) ================================= =========== =================================================================================== Example for agent named **agent_foo**: .. code-block:: properties agent_foo.sinkgroups = group1 agent_foo.sinkgroups.group1.sinks = sink1 sink2 agent_foo.sinkgroups.group1.processor.type = failover agent_foo.sinkgroups.group1.processor.priority.sink1 = 5 agent_foo.sinkgroups.group1.processor.priority.sink2 = 10 agent_foo.sinkgroups.group1.processor.maxpenalty = 10000 Load balancing Sink Processor ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Load balancing sink processor provides the ability to load-balance flow over multiple sinks. It maintains an indexed list of active sinks on which the load must be distributed. Implementation supports distributing load using either via ``ROUND_ROBIN`` or via ``RANDOM`` selection mechanism. The choice of selection mechanism defaults to ``ROUND_ROBIN`` type, but can be overridden via configuration. Custom selection mechanisms are supported via custom classes that inherits from ``LoadBalancingSelector``. When invoked, this selector picks the next sink using its configured selection mechanism and invokes it. In case the selected sink fails to deliver the event, the processor picks the next available sink via its configured selection mechanism. This implementation does not blacklist the failing sink and instead continues to optimistically attempt every available sink. If all sinks invocations result in failure, the selector propagates the failure to the sink runner. Required properties are in **bold**. ============================= =============== =============================================================== Property Name Default Description ============================= =============== =============================================================== **processor.sinks** -- Space separated list of sinks that are participating in the group **processor.type** ``default`` The component type name, needs to be ``load_balance`` processor.selector ``ROUND_ROBIN`` Selection mechanism. Must be either ``ROUND_ROBIN``, ``RANDOM`` or custom FQDN to class that inherits from ``LoadBalancingSelector`` ============================= =============== =============================================================== Example for agent named **agent_foo**: .. code-block:: properties agent_foo.sinkgroups = group1 agent_foo.sinkgroups.group1.sinks = sink1 sink2 agent_foo.sinkgroups.group1.processor.type = load_balance agent_foo.sinkgroups.group1.processor.selector = random Custom Sink Processor ~~~~~~~~~~~~~~~~~~~~~ Custom sink processors are not supported at the moment. Flume Interceptors ------------------ Flume has the capability to modify/drop events in-flight. This is done with the help of interceptors. Interceptors are classes that implement ``org.apache.flume.interceptor.Interceptor`` interface. An interceptor can modify or even drop events based on any criteria chosen by the developer of the interceptor. Flume supports chaining of interceptors. This is made possible through by specifying the list of interceptor builder class names in the configuration. Interceptors are specified as a whitespace separated list in the source configuration. The order in which the interceptors are specified is the order in which they are invoked. The list of events returned by one interceptor is passed to the next interceptor in the chain. Interceptors can modify or drop events. If an interceptor needs to drop events, it just does not return that event in the list that it returns. If it is to drop all events, then it simply returns an empty list. Interceptors are named components, here is an example of how they are created through configuration: .. code-block:: properties agent_foo.sources = source_foo agent_foo.channels = channel-1 agent_foo.sources.source_foo.interceptors = a b agent_foo.sources.source_foo.interceptors.a.type = org.apache.flume.interceptor.HostInterceptor$Builder agent_foo.sources.source_foo.interceptors.a.preserveExisting = false agent_foo.sources.source_foo.interceptors.a.hostHeader = hostname agent_foo.sources.source_foo.interceptors.b.type = org.apache.flume.interceptor.TimestampInterceptor$Builder Note that the interceptor builders are passed to the type config parameter. The interceptors are themselves configurable and can be passed configuration values just like they are passed to any other configurable component. In the above example, events are passed to the HostInterceptor first and the events returned by the HostInterceptor are then passed along to the TimestampInterceptor. Timestamp Interceptor ~~~~~~~~~~~~~~~~~~~~~ This interceptor inserts into the event headers, the time in millis at which it processes the event. This interceptor inserts a header with key ``timestamp`` whose value is the relevant timestamp. This interceptor can preserve an existing timestamp if it is already present in the configuration. ================ ======= ======================================================================== Property Name Default Description ================ ======= ======================================================================== type -- The component type name, has to be ``TIMESTAMP`` preserveExisting false If the timestamp already exists, should it be preserved - true or false ================ ======= ======================================================================== Host Interceptor ~~~~~~~~~~~~~~~~ This interceptor inserts the hostname or IP address of the host that this agent is running on. It inserts a header with key ``host`` or a configured key whose value is the hostname or IP address of the host, based on configuration. ================ ======= ======================================================================== Property Name Default Description ================ ======= ======================================================================== type -- The component type name, has to be ``HOST`` preserveExisting false If the host header already exists, should it be preserved - true or false useIP true Use the IP Address if true, else use hostname. hostHeader host The header key to be used. ================ ======= ======================================================================== In the example above, the key used in the event headers is "hostname" Flume Properties ---------------- ========================= ======= ==================================================================== Property Name Default Description ========================= ======= ==================================================================== flume.called.from.service -- If this property is specified then the Flume agent will continue polling for the config file even if the config file is not found at the expected location. Otherwise, the Flume agent will terminate if the config doesn't exist at the expected location. No property value is needed when setting this property (eg, just specifying -Dflume.called.from.service is enough) ========================= ======= ==================================================================== Property: flume.called.from.service ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Flume periodically polls, every 30 seconds, for changes to the specified config file. A Flume agent loads a new configuration from the config file if either an existing file is polled for the first time, or if an existing file's modification date has changed since the last time it was polled. Renaming or moving a file does not change its modification time. When a Flume agent polls a non-existent file then one of two things happens: 1. When the agent polls a non-existent config file for the first time, then the agent behaves according to the flume.called.from.service property. If the property is set, then the agent will continue polling (always at the same period -- every 30 seconds). If the property is not set, then the agent immediately terminates. ...OR... 2. When the agent polls a non-existent config file and this is not the first time the file is polled, then the agent makes no config changes for this polling period. The agent continues polling rather than terminating. Log4J Appender ============== Appends Log4j events to a flume agent's avro source. A client using this appender must have the flume-ng-sdk in the classpath (eg, flume-ng-sdk-1.2.0.jar). Required properties are in **bold**. ============= ======= ========================================================================== Property Name Default Description ============= ======= ========================================================================== Hostname -- The hostname on which a remote Flume agent is running with an avro source. Port -- The port at which the remote Flume agent's avro source is listening. ============= ======= ========================================================================== Sample log4j.properties file: .. code-block:: properties #... log4j.appender.flume = org.apache.flume.clients.log4jappender.Log4jAppender log4j.appender.flume.Hostname = example.com log4j.appender.flume.Port = 41414 # configure a class's logger to output to the flume appender log4j.logger.org.example.MyClass = DEBUG,flume #... Security ======== The HDFS sink supports Kerberos authentication if the underlying HDFS is running in secure mode. Please refer to the HDFS Sink section for configuring the HDFS sink Kerberos-related options. Monitoring ========== TBD Troubleshooting =============== Handling agent failures ----------------------- If the Flume agent goes down then the all the flows hosted on that agent are aborted. Once the agent is restarted, then flow will resume. The flow using jdbc or other stable channel will resume processing events where it left off. If the agent can't be restarted on the same, then there an option to migrate the database to another hardware and setup a new Flume agent that can resume processing the events saved in the db. The database HA futures can be leveraged to move the Flume agent to another host. Compatibility ------------- HDFS ~~~~ Currently Flume supports HDFS 0.20.2 and 0.23. AVRO ~~~~ TBD Additional version requirements ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TBD Tracing ------- TBD More Sample Configs ------------------- TBD Component Summary ================= ================================ ================== ==================================================================== Component Interface Type Implementation Class ================================ ================== ==================================================================== org.apache.flume.Channel MEMORY org.apache.flume.channel.MemoryChannel org.apache.flume.Channel JDBC org.apache.flume.channel.jdbc.JdbcChannel org.apache.flume.Channel -- org.apache.flume.channel.recoverable.memory.RecoverableMemoryChannel org.apache.flume.Channel FILE org.apache.flume.channel.file.FileChannel org.apache.flume.Channel -- org.apache.flume.channel.PseudoTxnMemoryChannel org.apache.flume.Channel -- org.example.MyChannel org.apache.flume.Source AVRO org.apache.flume.Source NETCAT org.apache.flume.Source SEQ org.apache.flume.Source EXEC org.apache.flume.Source SYSLOGTCP org.apache.flume.Source SYSLOGUDP org.apache.flume.Source -- org.apache.flume.source.avroLegacy.AvroLegacySource org.apache.flume.Source -- org.apache.flume.source.thriftLegacy.ThriftLegacySource org.apache.flume.Source -- org.example.MySource org.apache.flume.Sink NULL org.apache.flume.sink.NullSink org.apache.flume.Sink LOGGER org.apache.flume.sink.LoggerSink org.apache.flume.Sink AVRO org.apache.flume.sink.AvroSink org.apache.flume.Sink HDFS org.apache.flume.sink.hdfs.HDFSEventSink org.apache.flume.Sink -- org.apache.flume.sink.hbase.HBaseSink org.apache.flume.Sink -- org.apache.flume.sink.hbase.AsyncHBaseSink org.apache.flume.Sink FILE_ROLL org.apache.flume.sink.RollingFileSink org.apache.flume.Sink IRC org.apache.flume.sink.irc.IRCSink org.apache.flume.Sink -- org.example.MySink org.apache.flume.ChannelSelector REPLICATING org.apache.flume.channel.ReplicatingChannelSelector org.apache.flume.ChannelSelector MULTIPLEXING org.apache.flume.channel.MultiplexingChannelSelector org.apache.flume.ChannelSelector -- org.example.MyChannelSelector org.apache.flume.SinkProcessor DEFAULT org.apache.flume.sink.DefaultSinkProcessor org.apache.flume.SinkProcessor FAILOVER org.apache.flume.sink.FailoverSinkProcessor org.apache.flume.SinkProcessor LOAD_BALANCE org.apache.flume.sink.LoadBalancingSinkProcessor ================================ ================== ====================================================================