Configuring Atmosphere for Performance

Configuring your application to get the best performance of Atmosphere can be a difficult task. Please make sure you understand what is a Broadcaster before reading this document.

The first decision to make when configuring Atmosphere is to associate a Broadcaster with its own Thread Pool (ExecutorService) or use a single one, shared amongst the set of Broadcaster your application will create.

The second decision to make is to answer the following question: is message order important? Stated differently, does the order of invoking

broadcaster.broadcast("...");

is important for your application or not.

By default, the order is guarantee, e.g invoking

broadcaster.broadcast("message-1");
broadcaster.broadcast("message-2");
broadcaster.broadcast("message-3");

will be received by the client as:

message-1
message-2
message-3

If your application doesn't need to enforce messages order, you may want to disable the mechanism as it significantly improve the performance of messages delivery.

First, disable the mechanism by doing

<init-param>
   <param-name>org.atmosphere.cpr.Broadcaster.supportOutOfOrderBroadcast</param-name>
  <param-value>true</param-value>
</init-param>

Next, make sure you change the default Thread Pool that ship with Atmosphere as you may run out of memory, as the Thread pool is unbounded. Just set: To configure the maximum threads created by the Broadcaster of the message delivery, just add

        <init-param>
            <param-name>org.atmosphere.cpr.broadcaster.maxProcessingThreads</param-name>
            <param-value>10</param-value>
        </init-param>

and for the one used for the write operation,

        <init-param>
            <param-name>org.atmosphere.cpr.broadcaster.maxAsyncWriteThreads</param-name>
            <param-value>10</param-value>
        </init-param>

That could significantly improve the performance of your application.