Feeds

Feeds

Feeds within Apache Brooklyn are used to populate an entity's sensors. There are a variety of feed types, which commonly poll to retrieve the raw metrics of the entity (for example polling an HTTP management API, or over JMX).

Persistence

There are two ways to associate a feed with an entity.

The first way is (within the entity) to call feeds().addFeed(...). This persists the feed: the feed will be automatically added to the entity when the Brooklyn server restarts. It is important that all configuration of the feed is persistable (e.g. not using any in-line anonymous inner classes to define functions).

The feed builders can be passed a uniqueTag(...), which will be used to ensure that on rebind there will not be multiple copied of the feed (e.g. if rebind() had already re-created the feed).

The second way is to just pass to the feed's builder the entity. When using this mechanism, the feed will be wired up to the entity but it will not be persisted. In this case, it is important that the entity's rebind() method recreates the feed.

Types of Feed

HTTP Feed

An HttpFeed polls over http(s). An example is shown below:

private HttpFeed feed;

@Override
protected void connectSensors() {
  super.connectSensors();

  feed = feeds().addFeed(HttpFeed.builder()
      .period(200)
      .baseUri(String.format("http://%s:%s/management/subsystem/web/connector/http/read-resource", host, port))
      .baseUriVars(ImmutableMap.of("include-runtime","true"))
      .poll(new HttpPollConfig(SERVICE_UP)
          .onSuccess(HttpValueFunctions.responseCodeEquals(200))
          .onError(Functions.constant(false)))
      .poll(new HttpPollConfig(REQUEST_COUNT)
          .onSuccess(HttpValueFunctions.jsonContents("requestCount", Integer.class)))
      .build());
}

@Override
protected void disconnectSensors() {
  super.disconnectSensors();
  if (feed != null) feed.stop();
}

SSH Feed

An SSH feed executes a command over ssh periodically. An example is shown below:

private AbstractCommandFeed feed;

@Override
protected void connectSensors() {
  super.connectSensors();

  feed = feeds.addFeed(SshFeed.builder()
      .machine(mySshMachineLachine)
      .poll(new CommandPollConfig(SERVICE_UP)
          .command("rabbitmqctl -q status")
          .onSuccess(new Function() {
              public Boolean apply(SshPollValue input) {
                return (input.getExitStatus() == 0);
              }}))
      .build());
}

@Override
protected void disconnectSensors() {
  super.disconnectSensors();
  if (feed != null) feed.stop();
}

WinRm CMD Feed

A WinRM feed executes a windows command over winrm periodically. An example is shown below:

private AbstractCommandFeed feed;

//@Override
protected void connectSensors() {
  super.connectSensors();

  feed = feeds.addFeed(CmdFeed.builder()
                .entity(entity)
                .machine(machine)
                .poll(new CommandPollConfig<String>(SENSOR_STRING)
                        .command("ipconfig")
                        .onSuccess(SshValueFunctions.stdout()))
                .build());
}

@Override
protected void disconnectSensors() {
  super.disconnectSensors();
  if (feed != null) feed.stop();
}

Windows Performance Counter Feed

This type of feed retrieves performance counters from a Windows host, and posts the values to sensors.

One must supply a collection of mappings between Windows performance counter names and Brooklyn attribute sensors.

This feed uses WinRM to invoke the windows utility typeperf to query for a specific set of performance counters, by name. The values are extracted from the response, and published to the entity's sensors. An example is shown below:

private WindowsPerformanceCounterFeed feed;

@Override
protected void connectSensors() {
  feed = feeds.addFeed(WindowsPerformanceCounterFeed.builder()
      .addSensor("\\Processor(_total)\\% Idle Time", CPU_IDLE_TIME)
      .addSensor("\\Memory\\Available MBytes", AVAILABLE_MEMORY)
      .build());
}

@Override
protected void disconnectSensors() {
  super.disconnectSensors();
  if (feed != null) feed.stop();
}

JMX Feed

This type of feed queries over JMX to retrieve sensor values. This can query attribute values or call operations.

The JMX connection details can be automatically inferred from the entity's standard attributes, or it can be explicitly supplied.

An example is shown below:

private JmxFeed feed;

@Override
protected void connectSensors() {
  super.connectSensors();

  feed = feeds().addFeed(JmxFeed.builder()
      .period(5, TimeUnit.SECONDS)
      .pollAttribute(new JmxAttributePollConfig<Integer>(ERROR_COUNT)
          .objectName(requestProcessorMbeanName)
          .attributeName("errorCount"))
      .pollAttribute(new JmxAttributePollConfig<Boolean>(SERVICE_UP)
          .objectName(serverMbeanName)
          .attributeName("Started")
          .onError(Functions.constant(false)))
      .build());
}

Override
protected void disconnectSensors() {
  super.disconnectSensors();
  if (feed != null) feed.stop();
}

Function Feed

This type of feed periodically executes something to compute the attribute values. This can be a Callable, Supplier or Groovy Closure. It must be persistable (e.g. not use an in-line anonymous inner classes).

An example is shown below:

public static class ErrorCountRetriever implements Callable<Integer> {
  private final Entity entity;

  public ErrorCountRetriever(Entity entity) {
    this.entity = entity;
  }

  @Override
  public Integer call() throws Exception {
    // TODO your implementation...
    return 0;
  }
}

private FunctionFeed feed;

@Override
protected void connectSensors() {
  super.connectSensors();

  feed = feeds().addFeed(FunctionFeed.builder()
    .poll(new FunctionPollConfig<Object, Integer>(ERROR_COUNT)
        .period(500, TimeUnit.MILLISECONDS)
        .callable(new ErrorCountRetriever(this))
        .onExceptionOrFailure(Functions.<Integer>constant(null))
    .build());
}

@Override
protected void disconnectSensors() {
  super.disconnectSensors();
  if (feed != null) feed.stop();
}