GroupChannel (Apache Tomcat 6.0.53 API Documentation)
Keywords: org.apache.catalina.tribes.group.GroupChannel class

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## org.apache.catalina.tribes.group
Class GroupChannel

    java.lang.Object
      org.apache.catalina.tribes.group.ChannelInterceptorBase
          org.apache.catalina.tribes.group.GroupChannel

All Implemented Interfaces:
  Channel, ChannelInterceptor, Heartbeat, ManagedChannel, MembershipListener

    public class GroupChannel

extends ChannelInterceptorBase
implements ManagedChannel

The default implementation of a Channel.
The GroupChannel manages the replication channel. It coordinates message being sent and received with membership announcements. The channel has an chain of interceptors that can modify the message or perform other logic.
It manages a complete group, both membership and replication.

Author:
  Filip Hanik

Nested Class Summary
`static class` | `GroupChannel.HeartbeatThread` Title: Internal heartbeat thread Description: if `Channel.getHeartbeat()==true` then a thread of this class is created
`static class` | `GroupChannel.InterceptorIterator` Title: Interceptor Iterator Description: An iterator to loop through the interceptors in a channel

Nested classes/interfaces inherited from interface org.apache.catalina.tribes.ChannelInterceptor
`ChannelInterceptor.InterceptorEvent`

Field Summary
`protected java.util.ArrayList` | `channelListeners` A list of channel listeners that subscribe to incoming messages
`protected ChannelCoordinator` | `coordinator` The `ChannelCoordinator` coordinates the bottom layer components: - MembershipService - ChannelSender - ChannelReceiver
`protected GroupChannel.HeartbeatThread` | `hbthread` Internal heartbeat thread
`protected boolean` | `heartbeat` Flag to determine if the channel manages its own heartbeat If set to true, the channel will start a local thread for the heart beat.
`protected long` | `heartbeatSleeptime` If `heartbeat == true` then how often do we want this heartbeat to run. default is one minute
`protected ChannelInterceptor` | `interceptors` The first interceptor in the inteceptor stack.
`protected java.util.ArrayList` | `membershipListeners` A list of membership listeners that subscribe to membership announcements
`protected boolean` | `optionCheck` If set to true, the GroupChannel will check to make sure that

Fields inherited from class org.apache.catalina.tribes.group.ChannelInterceptorBase
`log, optionFlag`

Fields inherited from interface org.apache.catalina.tribes.Channel
`DEFAULT, MBR_RX_SEQ, MBR_TX_SEQ, SEND_OPTIONS_ASYNCHRONOUS, SEND_OPTIONS_BYTE_MESSAGE, SEND_OPTIONS_DEFAULT, SEND_OPTIONS_SECURE, SEND_OPTIONS_SYNCHRONIZED_ACK, SEND_OPTIONS_USE_ACK, SND_RX_SEQ, SND_TX_SEQ`

Constructor Summary
`GroupChannel()` Creates a GroupChannel.

Method Summary
`void` | `addChannelListener(ChannelListener channelListener)` Adds a channel listener to the channel.
`void` | `addInterceptor(ChannelInterceptor interceptor)` Adds an interceptor to the stack for message processing Interceptors are ordered in the way they are added.
`void` | `addMembershipListener(MembershipListener membershipListener)` Adds a membership listener to the channel.
`protected void` | `checkOptionFlags()` Validates the option flags that each interceptor is using and reports an error if two interceptor share the same flag.
`ChannelReceiver` | `getChannelReceiver()` Returns the channel receiver component
`ChannelSender` | `getChannelSender()` Returns the channel sender component
`ChannelInterceptor` | `getFirstInterceptor()` Returns the first interceptor of the stack.
`boolean` | `getHeartbeat()`
`long` | `getHeartbeatSleeptime()` Returns the sleep time in milliseconds that the internal heartbeat will sleep in between invokations of `Channel.heartbeat()`
`java.util.Iterator` | `getInterceptors()` Returns an iterator of all the interceptors in this stack
`MembershipService` | `getMembershipService()` Returns the membership service component
`boolean` | `getOptionCheck()`
`void` | `heartbeat()` Sends a heartbeat through the interceptor stack.
`void` | `memberAdded(Member member)` memberAdded gets invoked by the interceptor below the channel and the channel will broadcast it to the membership listeners
`void` | `memberDisappeared(Member member)` memberDisappeared gets invoked by the interceptor below the channel and the channel will broadcast it to the membership listeners
`void` | `messageReceived(ChannelMessage msg)` Callback from the interceptor stack.
`void` | `removeChannelListener(ChannelListener channelListener)` Removes a channel listener from the channel.
`void` | `removeMembershipListener(MembershipListener membershipListener)` Removes a membership listener from the channel.
`UniqueId` | `send(Member[] destination, java.io.Serializable msg, int options)` Send a message to the destinations specified
`UniqueId` | `send(Member[] destination, java.io.Serializable msg, int options, ErrorHandler handler)` Send a message to one or more members in the cluster
`protected void` | `sendNoRpcChannelReply(RpcMessage msg, Member destination)` Sends a `NoRpcChannelReply` message to a member This method gets invoked by the channel if a RPC message comes in and no channel listener accepts the message.
`void` | `setChannelReceiver(ChannelReceiver clusterReceiver)` Sets the channel receiver component
`void` | `setChannelSender(ChannelSender clusterSender)` Sets the channel sender component
`void` | `setHeartbeat(boolean heartbeat)` Enables or disables local heartbeat.
`void` | `setHeartbeatSleeptime(long heartbeatSleeptime)` Configure local heartbeat sleep time Only used when `getHeartbeat()==true`
`void` | `setMembershipService(MembershipService membershipService)` Sets the membership component
`void` | `setOptionCheck(boolean optionCheck)` Enables/disables the option check Setting this to true, will make the GroupChannel perform a conflict check on the interceptors.
`protected void` | `setupDefaultStack()` Sets up the default implementation interceptor stack if no interceptors have been added
`void` | `start(int svc)` Starts the channel
`void` | `stop(int svc)` Stops the channel

Methods inherited from class org.apache.catalina.tribes.group.ChannelInterceptorBase
`accept, fireInterceptorEvent, getLocalMember, getMember, getMembers, getNext, getOptionFlag, getPrevious, hasMembers, okToProcess, sendMessage, setNext, setOptionFlag, setPrevious`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Methods inherited from interface org.apache.catalina.tribes.Channel
`getLocalMember, getMember, getMembers, hasMembers`

Field Detail

### heartbeat

    protected boolean heartbeat

  Flag to determine if the channel manages its own heartbeat If set to true, the channel will start a local thread for the heart beat.

### heartbeatSleeptime

    protected long heartbeatSleeptime

  If `heartbeat == true` then how often do we want this heartbeat to run. default is one minute

### hbthread

    protected GroupChannel.HeartbeatThread hbthread

  Internal heartbeat thread

### coordinator

    protected ChannelCoordinator coordinator

  The `ChannelCoordinator` coordinates the bottom layer components:
  - MembershipService
  - ChannelSender
  - ChannelReceiver

### interceptors

    protected ChannelInterceptor interceptors

  The first interceptor in the inteceptor stack. The interceptors are chained in a linked list, so we only need a reference to the first one

### membershipListeners

    protected java.util.ArrayList membershipListeners

  A list of membership listeners that subscribe to membership announcements

### channelListeners

    protected java.util.ArrayList channelListeners

  A list of channel listeners that subscribe to incoming messages

### optionCheck

    protected boolean optionCheck

  If set to true, the GroupChannel will check to make sure that

Constructor Detail

### GroupChannel

    public GroupChannel()

  Creates a GroupChannel. This constructor will also add the first interceptor in the GroupChannel.
  The first interceptor is always the channel itself.

Method Detail

### addInterceptor

    public void addInterceptor(ChannelInterceptor interceptor)

  Adds an interceptor to the stack for message processing
  Interceptors are ordered in the way they are added.
  `channel.addInterceptor(A);`
  `channel.addInterceptor(C);`
  `channel.addInterceptor(B);`
  Will result in a interceptor stack like this:
  `A -> C -> B`
  The complete stack will look like this:
  `Channel -> A -> C -> B -> ChannelCoordinator`

  Specified by:
    `addInterceptor` in interface `Channel`
  Parameters:
    `interceptor` - ChannelInterceptorBase

### heartbeat

    public void heartbeat()

  Sends a heartbeat through the interceptor stack.
  Invoke this method from the application on a periodic basis if you have turned off internal heartbeats `channel.setHeartbeat(false)`

  Specified by:
    `heartbeat` in interface `Channel`
  Specified by:
    `heartbeat` in interface `ChannelInterceptor`
  Specified by:
    `heartbeat` in interface `Heartbeat`
  Overrides:
    `heartbeat` in class `ChannelInterceptorBase`
  See Also:
    `Channel.setHeartbeat(boolean)`

### send

    public UniqueId send(Member[] destination,
                         java.io.Serializable msg,
                         int options)
                  throws ChannelException

  Send a message to the destinations specified

  Specified by:
    `send` in interface `Channel`
  Parameters:
    `destination` - Member[] - destination.length > 1
    `msg` - Serializable - the message to send
    `options` - int - sender options, options can trigger guarantee levels and different interceptors to react to the message see class documentation for the `Channel` object.
  Returns:
    UniqueId - the unique Id that was assigned to this message
  Throws:
    `ChannelException` - - if an error occurs processing the message
  See Also:
    `Channel`

### send

    public UniqueId send(Member[] destination,
                         java.io.Serializable msg,
                         int options,
                         ErrorHandler handler)
                  throws ChannelException

  Description copied from interface: `Channel`
  Send a message to one or more members in the cluster

  Specified by:
    `send` in interface `Channel`
  Parameters:
    `destination` - Member[] - destination.length > 1
    `msg` - Serializable - the message to send
    `options` - int - sender options, options can trigger guarantee levels and different interceptors to react to the message see class documentation for the `Channel` object.
    `handler` - - callback object for error handling and completion notification, used when a message is sent asynchronously using the `Channel.SEND_OPTIONS_ASYNCHRONOUS` flag enabled.
  Returns:
    UniqueId - the unique Id that was assigned to this message
  Throws:
    `ChannelException` - - if an error occurs processing the message
  See Also:
    `Channel`

### messageReceived

    public void messageReceived(ChannelMessage msg)

  Callback from the interceptor stack.
  When a message is received from a remote node, this method will be invoked by the previous interceptor.
  This method can also be used to send a message to other components within the same application, but its an extreme case, and you're probably better off doing that logic between the applications itself.

  Specified by:
    `messageReceived` in interface `ChannelInterceptor`
  Overrides:
    `messageReceived` in class `ChannelInterceptorBase`
  Parameters:
    `msg` - ChannelMessage

### sendNoRpcChannelReply

    protected void sendNoRpcChannelReply(RpcMessage msg,
                                         Member destination)

  Sends a `NoRpcChannelReply` message to a member
  This method gets invoked by the channel if a RPC message comes in and no channel listener accepts the message. This avoids timeout

  Parameters:
    `msg` - RpcMessage
    `destination` - Member - the destination for the reply

### memberAdded

    public void memberAdded(Member member)

  memberAdded gets invoked by the interceptor below the channel and the channel will broadcast it to the membership listeners

  Specified by:
    `memberAdded` in interface `MembershipListener`
  Overrides:
    `memberAdded` in class `ChannelInterceptorBase`
  Parameters:
    `member` - Member - the new member

### memberDisappeared

    public void memberDisappeared(Member member)

  memberDisappeared gets invoked by the interceptor below the channel and the channel will broadcast it to the membership listeners

  Specified by:
    `memberDisappeared` in interface `MembershipListener`
  Overrides:
    `memberDisappeared` in class `ChannelInterceptorBase`
  Parameters:
    `member` - Member - the member that left or crashed
  See Also:
    `Member.SHUTDOWN_PAYLOAD`

### setupDefaultStack

    protected void setupDefaultStack()
                              throws ChannelException

  Sets up the default implementation interceptor stack if no interceptors have been added

  Throws:
    `ChannelException`

### checkOptionFlags

    protected void checkOptionFlags()
                             throws ChannelException

  Validates the option flags that each interceptor is using and reports an error if two interceptor share the same flag.

  Throws:
    `ChannelException`

### start

    public void start(int svc)
               throws ChannelException

  Starts the channel

  Specified by:
    `start` in interface `Channel`
  Specified by:
    `start` in interface `ChannelInterceptor`
  Overrides:
    `start` in class `ChannelInterceptorBase`
  Parameters:
    `svc` - int - what service to start
  Throws:
    `ChannelException`
  See Also:
    `Channel.start(int)`

### stop

    public void stop(int svc)
              throws ChannelException

  Stops the channel

  Specified by:
    `stop` in interface `Channel`
  Specified by:
    `stop` in interface `ChannelInterceptor`
  Overrides:
    `stop` in class `ChannelInterceptorBase`
  Parameters:
    `svc` - int
  Throws:
    `ChannelException`
  See Also:
    `Channel.stop(int)`

### getFirstInterceptor

    public ChannelInterceptor getFirstInterceptor()

  Returns the first interceptor of the stack. Useful for traversal.

  Returns:
    ChannelInterceptor

### getChannelReceiver

    public ChannelReceiver getChannelReceiver()

  Returns the channel receiver component

  Specified by:
    `getChannelReceiver` in interface `ManagedChannel`
  Returns:
    ChannelReceiver
  See Also:
    `ChannelReceiver`

### getChannelSender

    public ChannelSender getChannelSender()

  Returns the channel sender component

  Specified by:
    `getChannelSender` in interface `ManagedChannel`
  Returns:
    ChannelSender
  See Also:
    `ChannelSender`

### getMembershipService

    public MembershipService getMembershipService()

  Returns the membership service component

  Specified by:
    `getMembershipService` in interface `ManagedChannel`
  Returns:
    MembershipService
  See Also:
    `MembershipService`

### setChannelReceiver

    public void setChannelReceiver(ChannelReceiver clusterReceiver)

  Sets the channel receiver component

  Specified by:
    `setChannelReceiver` in interface `ManagedChannel`
  Parameters:
    `clusterReceiver` - ChannelReceiver
  See Also:
    `ChannelReceiver`

### setChannelSender

    public void setChannelSender(ChannelSender clusterSender)

  Sets the channel sender component

  Specified by:
    `setChannelSender` in interface `ManagedChannel`
  Parameters:
    `clusterSender` - ChannelSender
  See Also:
    `ChannelSender`

### setMembershipService

    public void setMembershipService(MembershipService membershipService)

  Sets the membership component

  Specified by:
    `setMembershipService` in interface `ManagedChannel`
  Parameters:
    `membershipService` - MembershipService
  See Also:
    `MembershipService`

### addMembershipListener

    public void addMembershipListener(MembershipListener membershipListener)

  Adds a membership listener to the channel.
  Membership listeners are uniquely identified using the equals(Object) method

  Specified by:
    `addMembershipListener` in interface `Channel`
  Parameters:
    `membershipListener` - MembershipListener
  See Also:
    `MembershipListener`

### removeMembershipListener

    public void removeMembershipListener(MembershipListener membershipListener)

  Removes a membership listener from the channel.
  Membership listeners are uniquely identified using the equals(Object) method

  Specified by:
    `removeMembershipListener` in interface `Channel`
  Parameters:
    `membershipListener` - MembershipListener
  See Also:
    `MembershipListener`

### addChannelListener

    public void addChannelListener(ChannelListener channelListener)

  Adds a channel listener to the channel.
  Channel listeners are uniquely identified using the equals(Object) method

  Specified by:
    `addChannelListener` in interface `Channel`
  Parameters:
    `channelListener` - ChannelListener
  See Also:
    `ChannelListener`, `Heartbeat`

### removeChannelListener

    public void removeChannelListener(ChannelListener channelListener)

  Removes a channel listener from the channel.
  Channel listeners are uniquely identified using the equals(Object) method

  Specified by:
    `removeChannelListener` in interface `Channel`
  Parameters:
    `channelListener` - ChannelListener
  See Also:
    `ChannelListener`

### getInterceptors

    public java.util.Iterator getInterceptors()

  Returns an iterator of all the interceptors in this stack

  Specified by:
    `getInterceptors` in interface `ManagedChannel`
  Returns:
    Iterator
  See Also:
    `Channel.addInterceptor(ChannelInterceptor)`

### setOptionCheck

    public void setOptionCheck(boolean optionCheck)

  Enables/disables the option check
  Setting this to true, will make the GroupChannel perform a conflict check on the interceptors. If two interceptors are using the same option flag and throw an error upon start.

  Parameters:
    `optionCheck` - boolean

### setHeartbeatSleeptime

    public void setHeartbeatSleeptime(long heartbeatSleeptime)

  Configure local heartbeat sleep time
  Only used when `getHeartbeat()==true`

  Parameters:
    `heartbeatSleeptime` - long - time in milliseconds to sleep between heartbeats

### setHeartbeat

    public void setHeartbeat(boolean heartbeat)

  Enables or disables local heartbeat. if `setHeartbeat(true)` is invoked then the channel will start an internal thread to invoke `Channel.heartbeat()` every `getHeartbeatSleeptime` milliseconds

  Specified by:
    `setHeartbeat` in interface `Channel`
  Parameters:
    `heartbeat` - boolean
  See Also:
    `Channel.heartbeat()`

### getOptionCheck

    public boolean getOptionCheck()

  Returns:
    boolean
  See Also:
    `setOptionCheck(boolean)`

### getHeartbeat

    public boolean getHeartbeat()

  Returns:
    boolean
  See Also:
    `setHeartbeat(boolean)`

### getHeartbeatSleeptime

    public long getHeartbeatSleeptime()

  Returns the sleep time in milliseconds that the internal heartbeat will sleep in between invokations of `Channel.heartbeat()`

  Returns:
    long

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