The Apache Tomcat Servlet/JSP Container

Apache Tomcat 7

Version 7.0.26, Feb 23 2012
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The Channel Interceptor object

Table of Contents
Introduction

Apache Tribes supports an interceptor architecture to intercept both messages and membership notifications. This architecture allows decoupling of logic and opens the way for some very kewl feature add ons.

Available Interceptors

  • org.apache.catalina.tribes.group.interceptors.TcpFailureDetector
  • org.apache.catalina.tribes.group.interceptors.ThroughputInterceptor
  • org.apache.catalina.tribes.group.interceptors.MessageDispatch15Interceptor
  • org.apache.catalina.tribes.group.interceptors.MessageDispatchInterceptor
  • org.apache.catalina.tribes.group.interceptors.NonBlockingCoordinator
  • org.apache.catalina.tribes.group.interceptors.OrderInterceptor
  • org.apache.catalina.tribes.group.interceptors.SimpleCoordinator
  • org.apache.catalina.tribes.group.interceptors.StaticMembershipInterceptor
  • org.apache.catalina.tribes.group.interceptors.TwoPhaseCommitInterceptor
  • org.apache.catalina.tribes.group.interceptors.DomainFilterInterceptor
  • org.apache.catalina.tribes.group.interceptors.FragmentationInterceptor
  • org.apache.catalina.tribes.group.interceptors.GzipInterceptor

Static Membership

In addition to dynamic discovery, Apache Tribes also supports static membership, with membership verification. To achieve this add the org.apache.catalina.tribes.group.interceptors.StaticMembershipInterceptor underneath the org.apache.catalina.tribes.group.interceptors.TcpFailureDetector interceptor. Inside the StaticMembershipInterceptor you can add the static members you wish to have. The TcpFailureDetector will do a health check on the static members,and also monitor them for crashes so they will have the same level of notification mechanism as the members that are automatically discovered.

     <Interceptor className="org.apache.catalina.tribes.group.interceptors.StaticMembershipInterceptor">
       <Member className="org.apache.catalina.tribes.membership.StaticMember"
                  port="5678"
                  securePort="-1"
                  host="tomcat01.mydomain.com"
                  domain="staging-cluster"
                  uniqueId="{0,1,2,3,4,5,6,7,8,9}"/>
     </Interceptor>

   

Attributes
Common Attributes
AttributeDescription
className Required, as there is no default
optionFlag If you want the interceptor to trigger on certain message depending on the message's option flag, you can setup the interceptors flag here. The default value is 0, meaning this interceptor will trigger on all messages.
org.apache.catalina.tribes.group.interceptors.DomainFilterInterceptor Attributes
AttributeDescription
domain The logical cluster domain that this Interceptor accepts. Two different type of values are possible:
1. Regular string values like "staging-domain" or "tomcat-cluster" will be converted into bytes using ISO-8859-1 encoding.
2. byte array in string form, for example {216,123,12,3}
org.apache.catalina.tribes.group.interceptors.MessageDispatch15Interceptor Attributes
AttributeDescription
className Required, This dispatcher uses JDK 1.5 java.util.concurrent package
optionFlag The default and hard coded value is 8 (org.apache.catalina.tribes.Channel.SEND_OPTIONS_ASYNCHRONOUS). The dispatcher will trigger on this value only, as it is predefined by Tribes. The other attributes are inherited from its base class org.apache.catalina.tribes.group.interceptors.MessageDispatchInterceptor.
org.apache.catalina.tribes.group.interceptors.MessageDispatchInterceptor Attributes
AttributeDescription
className Required, Same implementation as MessageDispatch15Interceptor, but with JDK 1.4 compliance.
optionFlag The default and hard coded value is 8 (org.apache.catalina.tribes.Channel.SEND_OPTIONS_ASYNCHRONOUS). The dispatcher will trigger on this value only, as it is predefined by Tribes.
alwaysSend What behavior should be executed when the dispatch queue is full. If true (default), then the message is is sent synchronously, if false an error is thrown.
maxQueueSize Size in bytes of the dispatch queue, the default value is 1024*1024*64 (64MB) sets the maximum queue size for the dispatch queue if the queue fills up, one can trigger the behavior, if alwaysSend is set to true, the message will be sent synchronously if the flag is false, an error is thrown
org.apache.catalina.tribes.group.interceptors.TcpFailureDetector Attributes
AttributeDescription
org.apache.catalina.tribes.group.interceptors.ThroughputInterceptor Attributes
AttributeDescription
interval Defines the interval in number of messages when we are to report the throughput statistics. The report is logged to the org.apache.juli.logging.LogFactory.getLog(ThroughputInterceptor.class) logger under the INFO level. Default value is to report every 10000 messages.
Nested element StaticMember Attributes
AttributeDescription
className Only one implementation available:org.apache.catalina.tribes.membership.StaticMember
port The port that this static member listens to for cluster messages
securePort The secure port this static member listens to for encrypted cluster messages default value is -1, this value means the member is not listening on a secure port
host The host (or network interface) that this static member listens for cluster messages. Three different type of values are possible:
1. IP address in the form of "216.123.1.23"
2. Hostnames like "tomcat01.mydomain.com" or "tomcat01" as long as they resolve correctly
3. byte array in string form, for example {216,123,12,3}
domain The logical cluster domain for this this static member listens for cluster messages. Two different type of values are possible:
1. Regular string values like "staging-domain" or "tomcat-cluster" will be converted into bytes using ISO-8859-1 encoding. 2. byte array in string form, for example {216,123,12,3}
uniqueId A universally uniqueId for this static member. The values must be 16 bytes in the following form:
1. byte array in string form, for example {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}

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