Dropwizard Websocket Support

[//]: # ()

A 3rd party Dropwizard bundle, that enhances Dropwizard capabilities to support not only JAX-RS resources but also websockets endpoints using the JSR-356 API.

The websockets endpoints will be instrumented the same way Dropwizards does with JAX-RS resources, and their metrics will be exposed in the same way. This includes:

• Counters of current open sessions.
• Counters and rate meters for new connections.
• Counters and rate meters for messages reviewed by the endpoint.
• Timers and statistics for session duration.

Maven Dependency

Add the Maven dependency:

<dependency>
  <groupId>com.liveperson</groupId>
  <artifactId>dropwizard-websockets</artifactId>
  <version></version>
</dependency>

Usage

In your code you should add the WebsocketBundle in the initialization stage of the Application. Give the bundle your endpoints classes (or ServerEndpoindConfig in case of programmatic endpoints) as parameters:

public void initialize(Bootstrap<Configuration> bootstrap) {
    bootstrap.addBundle(new WebsocketBundle(MyWebSocket1.class, MyWebSocket2.class));
}

Or, if you prefer, you can register the endpoint before the running stage:

public void initialize(Bootstrap<Configuration> bootstrap) {
    websocketBundle = new WebsocketBundle();        
    bootstrap.addBundle(websocketBundle);
}

@Override
public void run(Configuration configuration, Environment environment) throws Exception {
    // Using BasicServerEndpointConfig lets you inject objects to the websocket endpoint:
    final BasicServerEndpointConfig bsec = new BasicServerEndpointConfig(EchoServer.class, "/extends-ws");
    // bsec.getUserProperties().put(Environment.class.getName(), environment);
    // Then you can get it from the Session object
    // - obj = session.getUserProperties().get("objectName");            
    websocketBundle.addEndpoint(bsec);
}

That's all. A full example can be found in the tests classes.

Metrics

In order to collect metrics on your endpoints, you should annotate them with metrics annotations:

@Metered
@Timed
@ExceptionMetered
@ServerEndpoint("/annotated-ws")
public static class AnnotatedEchoServer {
    @OnOpen
    public void myOnOpen(final Session session) throws IOException {
        session.getAsyncRemote().sendText("welcome");
    }

    @OnMessage
    public void myOnMsg(final Session session, String message) {
        session.getAsyncRemote().sendText(message.toUpperCase());
    }

    @OnClose
    public void myOnClose(final Session session, CloseReason cr) {
    }
}

Then you'll be able to see your metrics as follows:

{
  "counters" : {
    "io.dropwizard.websockets.MyApp$AnnotatedEchoServer.openConnections" : {
      "count" : 2
    }
  },
  "meters" : {
    "io.dropwizard.websockets.MyApp$AnnotatedEchoServer.OnError" : {
      "count" : 0,
      "m15_rate" : 0.0,
      "m1_rate" : 0.0,
      "m5_rate" : 0.0,
      "mean_rate" : 0.0,
      "units" : "events/second"
    },
    "io.dropwizard.websockets.MyApp$AnnotatedEchoServer.OnMessage" : {
      "count" : 3,
      "m15_rate" : 0.6,
      "m1_rate" : 0.6,
      "m5_rate" : 0.6,
      "mean_rate" : 0.3194501069682357,
      "units" : "events/second"
    }
  },
  "timers" : {
    "io.dropwizard.websockets.MyApp$AnnotatedEchoServer" : {
      "count" : 1,
      "max" : 0.101819137,
      "mean" : 0.101819137,
      "min" : 0.101819137,
      "p50" : 0.101819137,
      "p75" : 0.101819137,
      "p95" : 0.101819137,
      "p98" : 0.101819137,
      "p99" : 0.101819137,
      "p999" : 0.101819137,
      "stddev" : 0.0,
      "m15_rate" : 0.2,
      "m1_rate" : 0.2,
      "m5_rate" : 0.2,
      "mean_rate" : 0.10647618704871187,
      "duration_units" : "seconds",
      "rate_units" : "calls/second"
    }
  }
}

Alternatives

See also dropwizard-websocket-jee7-bundle.