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<!DOCTYPE document [
  <!ENTITY project SYSTEM "project.xml">
]>
<document url="cluster-receiver.html">

  &project;

  <properties>
    <author email="fhanik@apache.org">Filip Hanik</author>
    <title>The Cluster Receiver object</title>
  </properties>

<body>

<section name="Table of Contents">
<toc/>
</section>

<section name="Introduction">
  <p>
  The receiver component is responsible for receiving cluster messages.
  As you might notice through the configuration, is that the receiving of messages
  and sending of messages are two different components, this is different from many other
  frameworks, but there is a good reason for it, to decouple the logic for how messages are sent from
  how messages are received.<br/>
  The receiver is very much like the Tomcat Connector, its the base of the thread pool
  for incoming cluster messages. The receiver is straight forward, but all the socket settings
  for incoming traffic are managed here.
  </p>
</section>

<section name="Blocking vs Non-Blocking Receiver">
  <p>
  The receiver supports both a non blocking, <code>org.apache.catalina.tribes.transport.nio.NioReceiver</code>, and a
  blocking, <code>org.apache.catalina.tribes.transport.bio.BioReceiver</code>. It is preferred to use the non blocking receiver
  to be able to grow your cluster without running into thread starvation.<br/>
  Using the non blocking receiver allows you to with a very limited thread count to serve a large number of messages.
  Usually the rule is to use 1 thread per node in the cluster for small clusters, and then depending on your message frequency
  and your hardware, you'll find an optimal number of threads peak out at a certain number.
  </p>
</section>

<section name="Attributes">
  <subsection name="Common Attributes">
  <attributes>
    <attribute name="className" required="true">
      The implementation of the receiver component. Two implementations available,
      <code>org.apache.catalina.tribes.transport.nio.NioReceiver</code> and
      <code>org.apache.catalina.tribes.transport.bio.BioReceiver</code>.<br/>
      The <code>org.apache.catalina.tribes.transport.nio.NioReceiver</code> is the
      preferred implementation
    </attribute>
    <attribute name="address" required="false">
      The address (network interface) to listen for incoming traffic.
      Same as the bind address. The default value is <code>auto</code> and translates to
      <code>java.net.InetAddress.getLocalHost().getHostAddress()</code>.
    </attribute>
    <attribute name="direct" required="false">
      Possible values are <code>true</code> or <code>false</code>.
      Set to true if you want the receiver to use direct bytebuffers when reading data
      from the sockets.
    </attribute>
    <attribute name="port" required="false">
      The listen port for incoming data. The default value is <code>4000</code>.
      To avoid port conflicts the receiver will automatically bind to a free port within the range of
      <code> port &lt;= bindPort &lt; port+autoBind</code>
      So for example, if port is 4000, and autoBind is set to 10, then the receiver will open up
      a server socket on the first available port in the range 4000-4009.
    </attribute>
    <attribute name="autoBind" required="false">
      Default value is <code>100</code>.
      Use this value if you wish to automatically avoid port conflicts the cluster receiver will try to open a
      server socket on the <code>port</code> attribute port, and then work up <code>autoBind</code> number of times.
    </attribute>
    <attribute name="securePort" required="false">
      The secure listen port. This port is SSL enabled. If this attribute is omitted no SSL port is opened up.
      There default value is unset, meaning there is no SSL socket available.
    </attribute>
    <attribute name="udpPort" required="false">
      The UDP listen port. If this attribute is omitted no UDP port is opened up.
      There default value is unset, meaning there is no UDP listener available.
    </attribute>
    <attribute name="selectorTimeout" required="false">
      The value in milliseconds for the polling timeout in the <code>NioReceiver</code>. On older versions of the JDK
      there have been bugs, that should all now be cleared out where the selector never woke up.
      The default value is a very high <code>5000</code> milliseconds.
    </attribute>
    <attribute name="maxThreads" required="false">
      The maximum number of threads in the receiver thread pool. The default value is <code>6</code>
      Adjust this value relative to the number of nodes in the cluster, the number of messages being exchanged and
      the hardware you are running on. A higher value doesn't mean more efficiency, tune this value according to your
      own test results.
    </attribute>
    <attribute name="minThreads" required="false">
      Minimum number of threads to be created when the receiver is started up. Default value is <code>6</code>
    </attribute>
    <attribute name="ooBInline" required="false">
      Boolean value for the socket OOBINLINE option. Possible values are <code>true</code> or <code>false</code>.
    </attribute>
    <attribute name="rxBufSize" required="false">
      The receiver buffer size on the receiving sockets. Value is in bytes, the default value is <code>43800</code> bytes.
    </attribute>
    <attribute name="txBufSize" required="false">
      The sending buffer size on the receiving sockets. Value is in bytes, the default value is <code>25188</code> bytes.
    </attribute>
    <attribute name="udpRxBufSize" required="false">
        The receive buffer size on the datagram socket.
        Default value is <code>25188</code> bytes.
    </attribute>
    <attribute name="udpTxBufSize" required="false">
       The send buffer size on the datagram socket.
       Default value is <code>43800</code> bytes.
    </attribute>
    <attribute name="soKeepAlive" required="false">
      Boolean value for the socket SO_KEEPALIVE option. Possible values are <code>true</code> or <code>false</code>.
    </attribute>
    <attribute name="soLingerOn" required="false">
      Boolean value to determine whether to use the SO_LINGER socket option.
      Possible values are <code>true</code> or <code>false</code>. Default value is <code>true</code>.
    </attribute>
    <attribute name="soLingerTime" required="false">
      Sets the SO_LINGER socket option time value. The value is in seconds.
      The default value is <code>3</code> seconds.
    </attribute>
    <attribute name="soReuseAddress" required="false">
     Boolean value for the socket SO_REUSEADDR option. Possible values are <code>true</code> or <code>false</code>.
    </attribute>
    <attribute name="tcpNoDelay" required="false">
     Boolean value for the socket TCP_NODELAY option. Possible values are <code>true</code> or <code>false</code>.
     The default value is <code>true</code>
    </attribute>
    <attribute name="timeout" required="false">
     Sets the SO_TIMEOUT option on the socket. The value is in milliseconds and the default value is <code>3000</code>
     milliseconds.
    </attribute>
    <attribute name="useBufferPool" required="false">
     Boolean value whether to use a shared buffer pool of cached <code>org.apache.catalina.tribes.io.XByteBuffer</code>
     objects. If set to true, the XByteBuffer that is used to pass a message up the channel, will be recycled at the end
     of the requests. This means that interceptors in the channel must not maintain a reference to the object
     after the <code>org.apache.catalina.tribes.ChannelInterceptor#messageReceived</code> method has exited.
    </attribute>
  </attributes>
  </subsection>
  <subsection name="NioReceiver">
  </subsection>
  <subsection name="BioReceiver">
  </subsection>

</section>
</body>
</document>
