Apache Synapse FAQs
Welcome to Apache Synapse FAQs.
General(GeneralApache Synapse questions - Non technical)
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What is Apache Synapse?
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Apache Synapse is a lightweight and high-performance Enterprise Service
Bus (ESB).
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What makes Apache Synapse unique?
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Apache Synapse is fast and able to handle thousands of concurrent
connections
with constant memory usage. It comes with a rich set of mediators to
support almost any integration scenario out of the box. It is also
easily
extensible and highly customizable.
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What is the license?
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Apache Synapse comes with Apache 2.0 licence.
Mediation(Questions related to sequences, endpoints, proxies etc)
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What is a proxy service?
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A proxy service is a virtual service hosted on the ESB. It can accept
requests from service clients, just like a real Web Service. A proxy
service can process requests and forward them to an actual Web Service
(back end service) to be further processed. The responses coming back
from
the back end service can be routed back to the original client. Proxy
services are mostly used to expose an existing service over a different
transport, format or QoS configuration.
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What is a mediator?
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A mediator is the basic message processing unit in the ESB. A mediator
can take a message, carry out some predefined actions on it and output
the modified message. Apache Synapse ships with a range of mediators capable
of carrying out various tasks on input messages.
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What is a sequence?
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A sequence is an ordered list of mediators (a mediator chain). When a
sequence is given a message, it will go through all the mediators in the
sequence. A sequence can also handover messages to other sequences.
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What is an Endpoint?
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A logical representation of an actual endpoint or a group of endpoints
(i.e. Load Balancing and Fail Over).
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What are Local Entries?
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Local entries can be used to hold various configuration elements
required by sequences and proxy services. Usually they are used to hold
WSDLs, XSDs, XSLT files etc. A local entry can contain XML content as
well
as plain text content. A local entry can be configured to load content
from a remote file too.
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What is a Message Mediation?
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Managing and transforming the messages flowing between the client and a
service in an enterprise.
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What is Message Mediation?
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Mediating messages coming into a specific service by specifying the
target URI as a Synapse mediation service.
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What is Service Mediation?
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Mediating messages coming into a specific service by specifying the
target URI as a Synapse mediation service.
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What is a Message Store?
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Message Store is the storage for ESB messages. It can be an in-memory
store
or can be JMS store with an external Message Broker. You can always plug
your
own message store implementations as well.
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What is a Message Processor?
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Message processor can be used to implement different messaging and
integration patters along with Message stores. Message processors will
consume
the messages in message stores and do the processing of them.
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What is a Template?
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ESB Templates try to minimize this redundancy by creating prototypes
that
users can re-use and utilize as and when needed. This is very much
analogous
to classes and instances of classes where-as, a template is a class that
can be used to wield instance objects such as templates and endpoints.
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What is the REST Api?
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REST Api can be used to mediate HTTP POST, GET, PUT and DELETE request
through Synapse and to integrate various RESTful services.
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Can Endpoint perform error handling?
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Yes. Endpoints can do error handling. User can configure the behavior
of an endpoints when it faced to a erroneous situation.
Transports(Transport related questions)
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What are the transports supported by the Apache Synapse?
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HTTP, HTTPS, VFS based file transport, FIX, Hessian, HL7,UDP, JMS, Mail,
TCP, XMPP
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Do I need an external JMS broker for the JMS transport?
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Yes, Apache Synapse requires an external JMS broker like Apache ActiveMQ
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Does Apache Synapse support two way JMS scenario (request/response) ?
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Yes, you can refer sample 264 which demonstrates exactly the JMS
request/response scenario.
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What is the NHTTP transport?
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This is the default HTTP transport used by Apache Synapse. NHTTP stands for
non-blocking HTTP. NHTTP transport uses the Java Non-blocking I/O API.
This allows the NHTTP transport to scale into handling hundreds of connections
without blocking the threads. The server worker threads used by the NHTTP
transport do not get blocked on I/O until the Synapse receives responses
for the already forwarded requests. Therefore Apache Synapse can accept
more concurrent connections and requests than most HTTP server products.
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What is the underlying HTTP library used by the NHTTP transport?
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NHTTP transport uses the Apache Http Core NIO library underneath. This
library provides low level I/O handling and HTTP level detail handling.