All Known Subinterfaces:: ManagedChannel

All Known Implementing Classes:: GroupChannel

public interface Channel

Channel interface
A channel is a representation of a group of nodes all participating in some sort of communication with each other.
The channel is the main API class for Tribes, this is essentially the only class that an application needs to be aware of. Through the channel the application can:
1. send messages
2. receive message (by registering a ChannelListener
3. get all members of the group getMembers()
4. receive notifications of members added and members disappeared by registering a MembershipListener

The channel has 5 major components:
1. Data receiver, with a built in thread pool to receive messages from other peers
2. Data sender, an implementation for sending data using NIO or java.io
3. Membership listener,listens for membership broadcasts
4. Membership broadcaster, broadcasts membership pings.
5. Channel interceptors, the ability to manipulate messages as they are sent or arrive

The channel layout is:


  ChannelListener_1..ChannelListener_N MembershipListener_1..MembershipListener_N [Application Layer]
            \          \                  /                   /
             \          \                /                   /
              \          \              /                   /
               \          \            /                   /
                \          \          /                   /
                 \          \        /                   /
                  ---------------------------------------
                                  |
                                  |
                               Channel
                                  |
                         ChannelInterceptor_1
                                  |                                               [Channel stack]
                         ChannelInterceptor_N
                                  |
                             Coordinator (implements MessageListener,MembershipListener,ChannelInterceptor)
                          --------------------
                         /        |           \
                        /         |            \
                       /          |             \
                      /           |              \
                     /            |               \
           MembershipService ChannelSender ChannelReceiver                        [IO layer]

For example usage @see org.apache.catalina.tribes.group.GroupChannel

Field Summary

Fields
Modifier and Type	Field	Description
`static int`	`DEFAULT`	Start and stop sequences can be controlled by these constants This allows you to start separate components of the channel DEFAULT - starts or stops all components in the channel
`static int`	`MBR_RX_SEQ`	Start and stop sequences can be controlled by these constants This allows you to start separate components of the channel MBR_RX_SEQ - starts or stops the membership listener.
`static int`	`MBR_TX_SEQ`	Start and stop sequences can be controlled by these constants This allows you to start separate components of the channel MBR_TX_SEQ - starts or stops the membership broadcaster.
`static int`	`SEND_OPTIONS_ASYNCHRONOUS`	Send options, when a message is sent, it can have an option flag to trigger certain behavior.
`static int`	`SEND_OPTIONS_BYTE_MESSAGE`	Send options, when a message is sent, it can have an option flag to trigger certain behavior.
`static int`	`SEND_OPTIONS_DEFAULT`	Send options, when a message is sent, it can have an option flag to trigger certain behavior.
`static int`	`SEND_OPTIONS_MULTICAST`	Send options.
`static int`	`SEND_OPTIONS_SECURE`	Send options, when a message is sent, it can have an option flag to trigger certain behavior.
`static int`	`SEND_OPTIONS_SYNCHRONIZED_ACK`	Send options, when a message is sent, it can have an option flag to trigger certain behavior.
`static int`	`SEND_OPTIONS_UDP`	Send options.
`static int`	`SEND_OPTIONS_USE_ACK`	Send options, when a message is sent, it can have an option flag to trigger certain behavior.
`static int`	`SND_RX_SEQ`	Start and stop sequences can be controlled by these constants This allows you to start separate components of the channel SND_RX_SEQ - starts or stops the data receiver.
`static int`	`SND_TX_SEQ`	Start and stop sequences can be controlled by these constants This allows you to start separate components of the channel SND_TX_SEQ - starts or stops the data sender.

Method Summary

All Methods Static Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`void`	`addChannelListener(ChannelListener listener)`	Add a channel listener, this is a callback object when messages are received If the channel listener implements the Heartbeat interface the `heartbeat()` method will be invoked when the heartbeat runs on the channel
`void`	`addInterceptor(ChannelInterceptor interceptor)`	Adds an interceptor to the channel message chain.
`void`	`addMembershipListener(MembershipListener listener)`	Add a membership listener, will get notified when a new member joins, leaves or crashes If the membership listener implements the Heartbeat interface the `heartbeat()` method will be invoked when the heartbeat runs on the channel
`Member`	`getLocalMember(boolean incAlive)`	Return the member that represents this node.
`Member`	`getMember(Member mbr)`	Returns the member from the membership service with complete and recent data.
`Member[]`	`getMembers()`	Get all current group members
`java.lang.String`	`getName()`	Return the name of this channel.
`static java.lang.String`	`getSendOptionsAsString(int input)`	Translates an integer value of SendOptions to its human-friendly comma separated value list for use in JMX and such.
`static int`	`getSendOptionValue(java.lang.String opt)`	Translates the name of an option to its integer value.
`java.util.concurrent.ScheduledExecutorService`	`getUtilityExecutor()`	Return executor that can be used for utility tasks.
`boolean`	`hasMembers()`	Returns true if there are any members in the group, this call is the same as `getMembers().length > 0`
`void`	`heartbeat()`	Sends a heart beat through the interceptor stacks Use this method to alert interceptors and other components to clean up garbage, timed out messages etc. If you application has a background thread, then you can save one thread, by configuring your channel to not use an internal heartbeat thread and invoking this method.
`static int`	`parseSendOptions(java.lang.String input)`	Translates a comma separated list of option names to their bitwise-ORd value
`void`	`removeChannelListener(ChannelListener listener)`	remove a channel listener, listeners are removed based on Object.hashCode and Object.equals
`void`	`removeMembershipListener(MembershipListener listener)`	remove a membership listener, listeners are removed based on Object.hashCode and Object.equals
`UniqueId`	`send(Member[] destination, java.io.Serializable msg, int options)`	Send a message to one or more members in the cluster
`UniqueId`	`send(Member[] destination, java.io.Serializable msg, int options, ErrorHandler handler)`	Send a message to one or more members in the cluster
`void`	`setHeartbeat(boolean enable)`	Enables or disables internal heartbeat.
`void`	`setName(java.lang.String name)`	Set the name of this channel
`void`	`setUtilityExecutor(java.util.concurrent.ScheduledExecutorService utilityExecutor)`	Set the executor that can be used for utility tasks.
`void`	`start(int svc)`	Starts up the channel.
`void`	`stop(int svc)`	Shuts down the channel.

- Field Detail
  - DEFAULT
```
static final int DEFAULT
```
    Start and stop sequences can be controlled by these constants This allows you to start separate components of the channel
    DEFAULT - starts or stops all components in the channel
    
    See Also:
    
    start(int), stop(int), Constant Field Values
  - SND_RX_SEQ
```
static final int SND_RX_SEQ
```
    Start and stop sequences can be controlled by these constants This allows you to start separate components of the channel
    SND_RX_SEQ - starts or stops the data receiver. Start means opening a server socket in case of a TCP implementation
    
    See Also:
    
    start(int), stop(int), Constant Field Values
  - SND_TX_SEQ
```
static final int SND_TX_SEQ
```
    Start and stop sequences can be controlled by these constants This allows you to start separate components of the channel
    SND_TX_SEQ - starts or stops the data sender. This should not open any sockets, as sockets are opened on demand when a message is being sent
    
    See Also:
    
    start(int), stop(int), Constant Field Values
  - MBR_RX_SEQ
```
static final int MBR_RX_SEQ
```
    Start and stop sequences can be controlled by these constants This allows you to start separate components of the channel
    MBR_RX_SEQ - starts or stops the membership listener. In a multicast implementation this will open a datagram socket and join a group and listen for membership messages members joining
    
    See Also:
    
    start(int), stop(int), Constant Field Values
  - MBR_TX_SEQ
```
static final int MBR_TX_SEQ
```
    Start and stop sequences can be controlled by these constants This allows you to start separate components of the channel
    MBR_TX_SEQ - starts or stops the membership broadcaster. In a multicast implementation this will open a datagram socket and join a group and broadcast the local member information
    
    See Also:
    
    start(int), stop(int), Constant Field Values
  - SEND_OPTIONS_BYTE_MESSAGE
```
static final int SEND_OPTIONS_BYTE_MESSAGE
```
    Send options, when a message is sent, it can have an option flag to trigger certain behavior. Most flags are used to trigger channel interceptors as the message passes through the channel stack.
    However, there are five default flags that every channel implementation must implement
    SEND_OPTIONS_BYTE_MESSAGE - The message is a pure byte message and no marshaling or unmarshaling will be performed.
    
    See Also:
    
    send(Member[], Serializable , int), send(Member[], Serializable, int, ErrorHandler), Constant Field Values
  - SEND_OPTIONS_USE_ACK
```
static final int SEND_OPTIONS_USE_ACK
```
    Send options, when a message is sent, it can have an option flag to trigger certain behavior. Most flags are used to trigger channel interceptors as the message passes through the channel stack.
    However, there are five default flags that every channel implementation must implement
    SEND_OPTIONS_USE_ACK - Message is sent and an ACK is received when the message has been received by the recipient
    If no ack is received, the message is not considered successful
    
    See Also:
    
    send(Member[], Serializable , int), send(Member[], Serializable, int, ErrorHandler), Constant Field Values
  - SEND_OPTIONS_SYNCHRONIZED_ACK
```
static final int SEND_OPTIONS_SYNCHRONIZED_ACK
```
    Send options, when a message is sent, it can have an option flag to trigger certain behavior. Most flags are used to trigger channel interceptors as the message passes through the channel stack.
    However, there are five default flags that every channel implementation must implement
    SEND_OPTIONS_SYNCHRONIZED_ACK - Message is sent and an ACK is received when the message has been received and processed by the recipient
    If no ack is received, the message is not considered successful
    
    See Also:
    
    send(Member[], Serializable , int), send(Member[], Serializable, int, ErrorHandler), Constant Field Values
  - SEND_OPTIONS_ASYNCHRONOUS
```
static final int SEND_OPTIONS_ASYNCHRONOUS
```
    Send options, when a message is sent, it can have an option flag to trigger certain behavior. Most flags are used to trigger channel interceptors as the message passes through the channel stack.
    However, there are five default flags that every channel implementation must implement
    SEND_OPTIONS_ASYNCHRONOUS - Message will be placed on a queue and sent by a separate thread
    If the queue is full, behaviour depends on MessageDispatchInterceptor.isAlwaysSend()
    
    See Also:
    
    send(Member[], Serializable , int), send(Member[], Serializable, int, ErrorHandler), Constant Field Values
  - SEND_OPTIONS_SECURE
```
static final int SEND_OPTIONS_SECURE
```
    Send options, when a message is sent, it can have an option flag to trigger certain behavior. Most flags are used to trigger channel interceptors as the message passes through the channel stack.
    However, there are five default flags that every channel implementation must implement
    SEND_OPTIONS_SECURE - Message is sent over an encrypted channel
    
    See Also:
    
    send(Member[], Serializable , int), send(Member[], Serializable, int, ErrorHandler), Constant Field Values
  - SEND_OPTIONS_UDP
```
static final int SEND_OPTIONS_UDP
```
    Send options. When a message is sent with this flag on the system sends the message using UDP instead of TCP
    
    See Also:
    
    send(Member[], Serializable , int), send(Member[], Serializable, int, ErrorHandler), Constant Field Values
  - SEND_OPTIONS_MULTICAST
```
static final int SEND_OPTIONS_MULTICAST
```
    Send options. When a message is sent with this flag on the system sends a UDP message on the Multicast address instead of UDP or TCP to individual addresses
    
    See Also:
    
    send(Member[], Serializable , int), send(Member[], Serializable, int, ErrorHandler), Constant Field Values
  - SEND_OPTIONS_DEFAULT
```
static final int SEND_OPTIONS_DEFAULT
```
    Send options, when a message is sent, it can have an option flag to trigger certain behavior. Most flags are used to trigger channel interceptors as the message passes through the channel stack.
    However, there are five default flags that every channel implementation must implement
    SEND_OPTIONS_DEFAULT - the default sending options, just a helper variable.
    The default is int SEND_OPTIONS_DEFAULT = SEND_OPTIONS_USE_ACK;
    
    See Also:
    
    SEND_OPTIONS_USE_ACK, send(Member[], Serializable , int), send(Member[], Serializable, int, ErrorHandler), Constant Field Values
- Method Detail
  - addInterceptor
```
void addInterceptor(ChannelInterceptor interceptor)
```
    Adds an interceptor to the channel message chain.
    
    Parameters:
    
    interceptor - ChannelInterceptor
  - start
```
void start(int svc)
    throws ChannelException
```
    Starts up the channel. This can be called multiple times for individual services to start The svc parameter can be the logical or value of any constants
    
    Parameters:
    
    svc - int value of
    DEFAULT - will start all services
    MBR_RX_SEQ - starts the membership receiver
    MBR_TX_SEQ - starts the membership broadcaster
    SND_TX_SEQ - starts the replication transmitter
    SND_RX_SEQ - starts the replication receiver
    Note: In order for the membership broadcaster to transmit the correct information, it has to be started after the replication receiver.
    
    Throws:
    
    ChannelException - if a startup error occurs or the service is already started or an error occurs.
  - stop
```
void stop(int svc)
   throws ChannelException
```
    Shuts down the channel. This can be called multiple times for individual services to shutdown The svc parameter can be the logical or value of any constants
    
    Parameters:
    
    svc - int value of
    DEFAULT - will shutdown all services
    MBR_RX_SEQ - stops the membership receiver
    MBR_TX_SEQ - stops the membership broadcaster
    SND_TX_SEQ - stops the replication transmitter
    SND_RX_SEQ - stops the replication receiver
    
    Throws:
    
    ChannelException - if a startup error occurs or the service is already stopped or an error occurs.
  - send
```
UniqueId send(Member[] destination,
              java.io.Serializable msg,
              int options)
       throws ChannelException
```
    Send a message to one or more members in the cluster
    
    Parameters:
    
    destination - Member[] - the destinations, cannot be null or zero length, the reason for that is that a membership change can occur and at that time the application is uncertain what group the message actually got sent to.
    
    msg - Serializable - the message to send, has to be serializable, or a ByteMessage to send a pure byte array
    
    options - int - sender options, see class documentation for each interceptor that is configured in order to trigger interceptors
    
    Returns:
    
    a unique Id that identifies the message that is sent
    
    Throws:
    
    ChannelException - if a serialization error happens.
    
    See Also:
    
    ByteMessage, SEND_OPTIONS_USE_ACK, SEND_OPTIONS_ASYNCHRONOUS, SEND_OPTIONS_SYNCHRONIZED_ACK
  - send
```
UniqueId send(Member[] destination,
              java.io.Serializable msg,
              int options,
              ErrorHandler handler)
       throws ChannelException
```
    Send a message to one or more members in the cluster
    
    Parameters:
    
    destination - Member[] - the destinations, null or zero length means all
    
    msg - ClusterMessage - the message to send
    
    options - int - sender options, see class documentation
    
    handler - ErrorHandler - handle errors through a callback, rather than throw it
    
    Returns:
    
    a unique Id that identifies the message that is sent
    
    Throws:
    
    ChannelException - - if a serialization error happens.
  - heartbeat
```
void heartbeat()
```
    Sends a heart beat through the interceptor stacks Use this method to alert interceptors and other components to clean up garbage, timed out messages etc.
    If you application has a background thread, then you can save one thread, by configuring your channel to not use an internal heartbeat thread and invoking this method.
    
    See Also:
    
    setHeartbeat(boolean)
  - setHeartbeat
```
void setHeartbeat(boolean enable)
```
    Enables or disables internal heartbeat.
    
    Parameters:
    
    enable - boolean - default value is implementation specific
    
    See Also:
    
    heartbeat()
  - addMembershipListener
```
void addMembershipListener(MembershipListener listener)
```
    Add a membership listener, will get notified when a new member joins, leaves or crashes
    If the membership listener implements the Heartbeat interface the heartbeat() method will be invoked when the heartbeat runs on the channel
    
    Parameters:
    
    listener - MembershipListener
    
    See Also:
    
    MembershipListener
  - addChannelListener
```
void addChannelListener(ChannelListener listener)
```
    Add a channel listener, this is a callback object when messages are received
    If the channel listener implements the Heartbeat interface the heartbeat() method will be invoked when the heartbeat runs on the channel
    
    Parameters:
    
    listener - ChannelListener
    
    See Also:
    
    ChannelListener, Heartbeat
  - removeMembershipListener
```
void removeMembershipListener(MembershipListener listener)
```
    remove a membership listener, listeners are removed based on Object.hashCode and Object.equals
    
    Parameters:
    
    listener - MembershipListener
    
    See Also:
    
    MembershipListener
  - removeChannelListener
```
void removeChannelListener(ChannelListener listener)
```
    remove a channel listener, listeners are removed based on Object.hashCode and Object.equals
    
    Parameters:
    
    listener - ChannelListener
    
    See Also:
    
    ChannelListener
  - hasMembers
```
boolean hasMembers()
```
    Returns true if there are any members in the group, this call is the same as getMembers().length > 0
    
    Returns:
    
    boolean - true if there are any members automatically discovered
  - getMembers
```
Member[] getMembers()
```
    Get all current group members
    
    Returns:
    
    all members or empty array, never null
  - getLocalMember
```
Member getLocalMember(boolean incAlive)
```
    Return the member that represents this node. This is also the data that gets broadcasted through the membership broadcaster component
    
    Parameters:
    
    incAlive - - optimization, true if you want it to calculate alive time since the membership service started.
    
    Returns:
    
    Member
  - getMember
```
Member getMember(Member mbr)
```
    Returns the member from the membership service with complete and recent data. Some implementations might serialize and send membership information along with a message, and instead of sending complete membership details, only send the primary identifier for the member but not the payload or other information. When such message is received the application can retrieve the cached member through this call.
    In most cases, this is not necessary.
    
    Parameters:
    
    mbr - Member
    
    Returns:
    
    Member
  - getName
```
java.lang.String getName()
```
    Return the name of this channel.
    
    Returns:
    
    channel name
  - setName
```
void setName(java.lang.String name)
```
    Set the name of this channel
    
    Parameters:
    
    name - The new channel name
  - getUtilityExecutor
```
java.util.concurrent.ScheduledExecutorService getUtilityExecutor()
```
    Return executor that can be used for utility tasks.
    
    Returns:
    
    the executor
  - setUtilityExecutor
```
void setUtilityExecutor(java.util.concurrent.ScheduledExecutorService utilityExecutor)
```
    Set the executor that can be used for utility tasks.
    
    Parameters:
    
    utilityExecutor - the executor
  - getSendOptionValue
```
static int getSendOptionValue(java.lang.String opt)
```
    Translates the name of an option to its integer value. Valid option names are "asynchronous" (alias "async"), "byte_message" (alias "byte"), "multicast", "secure", "synchronized_ack" (alias "sync"), "udp", "use_ack"
    
    Parameters:
    
    opt - The name of the option
    
    Returns:
    
    the int value of the passed option name
  - parseSendOptions
```
static int parseSendOptions(java.lang.String input)
```
    Translates a comma separated list of option names to their bitwise-ORd value
    
    Parameters:
    
    input - A comma separated list of options, e.g. "async, multicast"
    
    Returns:
    
    a bitwise ORd value of the passed option names
  - getSendOptionsAsString
```
static java.lang.String getSendOptionsAsString(int input)
```
    Translates an integer value of SendOptions to its human-friendly comma separated value list for use in JMX and such.
    
    Parameters:
    
    input - the int value of SendOptions
    
    Returns:
    
    the human-friendly string representation in a reverse order (i.e. the last option will be shown first)

Interface Channel

Field Summary

Method Summary

Field Detail

DEFAULT

SND_RX_SEQ

SND_TX_SEQ

MBR_RX_SEQ

MBR_TX_SEQ

SEND_OPTIONS_BYTE_MESSAGE

SEND_OPTIONS_USE_ACK

SEND_OPTIONS_SYNCHRONIZED_ACK

SEND_OPTIONS_ASYNCHRONOUS

SEND_OPTIONS_SECURE

SEND_OPTIONS_UDP

SEND_OPTIONS_MULTICAST

SEND_OPTIONS_DEFAULT

Method Detail

addInterceptor

start

stop

send

send

heartbeat

setHeartbeat

addMembershipListener

addChannelListener

removeMembershipListener

removeChannelListener

hasMembers

getMembers

getLocalMember

getMember

getName

setName

getUtilityExecutor

setUtilityExecutor

getSendOptionValue

parseSendOptions

getSendOptionsAsString