Configuring the maximum threads used by a Broadcaster - Atmosphere/atmosphere GitHub Wiki
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>