/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.catalina.tribes;
import java.io.Serializable;
/**
* Channel interface<br>
* A channel is a representation of a group of nodes all participating in some sort of
* communication with each other.<br>
* 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:<br>
* 1. send messages<br>
* 2. receive message (by registering a <code>ChannelListener</code><br>
* 3. get all members of the group <code>getMembers()</code><br>
* 4. receive notifications of members added and members disappeared by
* registerering a <code>MembershipListener</code><br>
* <br>
* The channel has 5 major components:<br>
* 1. Data receiver, with a built in thread pool to receive messages from other peers<br>
* 2. Data sender, an implementation for sending data using NIO or java.io<br>
* 3. Membership listener,listens for membership broadcasts<br>
* 4. Membership broadcaster, broadcasts membership pings.<br>
* 5. Channel interceptors, the ability to manipulate messages as they are sent or arrive<br><br>
* The channel layout is:
* <pre><code>
* 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]
* </code></pre>
*
* For example usage @see org.apache.catalina.tribes.group.GroupChannel
* @author Filip Hanik
*
*/
public interface Channel {
/**
* Start and stop sequences can be controlled by these constants
* This allows you to start separate components of the channel <br>
* DEFAULT - starts or stops all components in the channel
* @see #start(int)
* @see #stop(int)
*/
public static final int DEFAULT = 15;
/**
* Start and stop sequences can be controlled by these constants
* This allows you to start separate components of the channel <br>
* SND_RX_SEQ - starts or stops the data receiver. Start means opening a server socket
* in case of a TCP implementation
* @see #start(int)
* @see #stop(int)
*/
public static final int SND_RX_SEQ = 1;
/**
* Start and stop sequences can be controlled by these constants
* This allows you to start separate components of the channel <br>
* 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 #start(int)
* @see #stop(int)
*/
public static final int SND_TX_SEQ = 2;
/**
* Start and stop sequences can be controlled by these constants
* This allows you to start separate components of the channel <br>
* 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 #start(int)
* @see #stop(int)
*/
public static final int MBR_RX_SEQ = 4;
/**
* Start and stop sequences can be controlled by these constants
* This allows you to start separate components of the channel <br>
* 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 #start(int)
* @see #stop(int)
*/
public static final int MBR_TX_SEQ = 8;
/**
* 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. <br>
* However, there are five default flags that every channel implementation must implement<br>
* SEND_OPTIONS_BYTE_MESSAGE - The message is a pure byte message and no marshalling or unmarshalling will
* be performed.<br>
*
* @see #send(Member[], Serializable , int)
* @see #send(Member[], Serializable, int, ErrorHandler)
*/
public static final int SEND_OPTIONS_BYTE_MESSAGE = 0x0001;
/**
* 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. <br>
* However, there are five default flags that every channel implementation must implement<br>
* SEND_OPTIONS_USE_ACK - Message is sent and an ACK is received when the message has been received by the recipient<br>
* If no ack is received, the message is not considered successful<br>
* @see #send(Member[], Serializable , int)
* @see #send(Member[], Serializable, int, ErrorHandler)
*/
public static final int SEND_OPTIONS_USE_ACK = 0x0002;
/**
* 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. <br>
* However, there are five default flags that every channel implementation must implement<br>
* SEND_OPTIONS_SYNCHRONIZED_ACK - Message is sent and an ACK is received when the message has been received and
* processed by the recipient<br>
* If no ack is received, the message is not considered successful<br>
* @see #send(Member[], Serializable , int)
* @see #send(Member[], Serializable, int, ErrorHandler)
*/
public static final int SEND_OPTIONS_SYNCHRONIZED_ACK = 0x0004;
/**
* 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. <br>
* However, there are five default flags that every channel implementation must implement<br>
* SEND_OPTIONS_ASYNCHRONOUS - Message is sent and an ACK is received when the message has been received and
* processed by the recipient<br>
* If no ack is received, the message is not considered successful<br>
* @see #send(Member[], Serializable , int)
* @see #send(Member[], Serializable, int, ErrorHandler)
*/
public static final int SEND_OPTIONS_ASYNCHRONOUS = 0x0008;
/**
* 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. <br>
* However, there are five default flags that every channel implementation must implement<br>
* SEND_OPTIONS_SECURE - Message is sent over an encrypted channel<br>
* @see #send(Member[], Serializable , int)
* @see #send(Member[], Serializable, int, ErrorHandler)
*/
public static final int SEND_OPTIONS_SECURE = 0x0010;
/**
* 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. <br>
* However, there are five default flags that every channel implementation must implement<br>
* SEND_OPTIONS_DEFAULT - the default sending options, just a helper variable. <br>
* The default is <code>int SEND_OPTIONS_DEFAULT = SEND_OPTIONS_USE_ACK;</code><br>
* @see #SEND_OPTIONS_USE_ACK
* @see #send(Member[], Serializable , int)
* @see #send(Member[], Serializable, int, ErrorHandler)
*/
public static final int SEND_OPTIONS_DEFAULT = SEND_OPTIONS_USE_ACK;
/**
* Adds an interceptor to the channel message chain.
* @param interceptor ChannelInterceptor
*/
public void addInterceptor(ChannelInterceptor interceptor);
/**
* 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
* @param svc int value of <BR>
* DEFAULT - will start all services <BR>
* MBR_RX_SEQ - starts the membership receiver <BR>
* MBR_TX_SEQ - starts the membership broadcaster <BR>
* SND_TX_SEQ - starts the replication transmitter<BR>
* SND_RX_SEQ - starts the replication receiver<BR>
* <b>Note:</b> 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.
*/
public void start(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
* @param svc int value of <BR>
* DEFAULT - will shutdown all services <BR>
* MBR_RX_SEQ - stops the membership receiver <BR>
* MBR_TX_SEQ - stops the membership broadcaster <BR>
* SND_TX_SEQ - stops the replication transmitter<BR>
* SND_RX_SEQ - stops the replication receiver<BR>
* @throws ChannelException if a startup error occurs or the service is already stopped or an error occurs.
*/
public void stop(int svc) throws ChannelException;
/**
* Send a message to one or more members in the cluster
* @param destination Member[] - the destinations, can not 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.
* @param msg Serializable - the message to send, has to be serializable, or a <code>ByteMessage</code> to
* send a pure byte array
* @param options int - sender options, see class documentation for each interceptor that is configured in order to trigger interceptors
* @return a unique Id that identifies the message that is sent
* @see ByteMessage
* @see #SEND_OPTIONS_USE_ACK
* @see #SEND_OPTIONS_ASYNCHRONOUS
* @see #SEND_OPTIONS_SYNCHRONIZED_ACK
*/
public UniqueId send(Member[] destination, Serializable msg, int options) throws ChannelException;
/**
* Send a message to one or more members in the cluster
* @param destination Member[] - the destinations, null or zero length means all
* @param msg ClusterMessage - the message to send
* @param options int - sender options, see class documentation
* @param handler ErrorHandler - handle errors through a callback, rather than throw it
* @return a unique Id that identifies the message that is sent
* @exception ChannelException - if a serialization error happens.
*/
public UniqueId send(Member[] destination, Serializable msg, int options, ErrorHandler handler) throws ChannelException;
/**
* 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.<br>
* 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 #setHeartbeat(boolean)
*/
public void heartbeat();
/**
* Enables or disables internal heartbeat.
* @param enable boolean - default value is implementation specific
* @see #heartbeat()
*/
public void setHeartbeat(boolean enable);
/**
* Add a membership listener, will get notified when a new member joins, leaves or crashes
* <br>If the membership listener implements the Heartbeat interface
* the <code>heartbeat()</code> method will be invoked when the heartbeat runs on the channel
* @param listener MembershipListener
* @see MembershipListener
*/
public void addMembershipListener(MembershipListener listener);
/**
* Add a channel listener, this is a callback object when messages are received
* <br>If the channel listener implements the Heartbeat interface
* the <code>heartbeat()</code> method will be invoked when the heartbeat runs on the channel
* @param listener ChannelListener
* @see ChannelListener
* @see Heartbeat
*/
public void addChannelListener(ChannelListener listener);
/**
* remove a membership listener, listeners are removed based on Object.hashCode and Object.equals
* @param listener MembershipListener
* @see MembershipListener
*/
public void removeMembershipListener(MembershipListener listener);
/**
* remove a channel listener, listeners are removed based on Object.hashCode and Object.equals
* @param listener ChannelListener
* @see ChannelListener
*/
public void removeChannelListener(ChannelListener listener);
/**
* Returns true if there are any members in the group,
* this call is the same as <code>getMembers().length>0</code>
* @return boolean - true if there are any members automatically discovered
*/
public boolean hasMembers() ;
/**
* Get all current group members
* @return all members or empty array, never null
*/
public Member[] getMembers() ;
/**
* Return the member that represents this node. This is also the data
* that gets broadcasted through the membership broadcaster component
* @param incAlive - optimization, true if you want it to calculate alive time
* since the membership service started.
* @return Member
*/
public Member getLocalMember(boolean incAlive);
/**
* 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.<br>
* In most cases, this is not necessary.
* @param mbr Member
* @return Member
*/
public Member getMember(Member mbr);
}