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/*
* 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;
import org.apache.catalina.tribes.group.interceptors.MessageDispatchInterceptor;
/**
* 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
*
* @see org.apache.catalina.tribes.group.GroupChannel example usage
*/
public interface Channel {
/**
* 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 #start(int)
* @see #stop(int)
*/
int DEFAULT = 15;
/**
* 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 #start(int)
* @see #stop(int)
*/
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
* 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)
*/
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
* 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)
*/
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
* 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)
*/
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.
* 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 #send(Member[], Serializable , int)
* @see #send(Member[], Serializable, int, ErrorHandler)
*/
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.
* 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 #send(Member[], Serializable , int)
* @see #send(Member[], Serializable, int, ErrorHandler)
*/
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.
* 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 #send(Member[], Serializable , int)
* @see #send(Member[], Serializable, int, ErrorHandler)
*/
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.
* 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 {@link MessageDispatchInterceptor#isAlwaysSend()}
* @see #send(Member[], Serializable , int)
* @see #send(Member[], Serializable, int, ErrorHandler)
*/
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.
* However, there are five default flags that every channel implementation must implement
* SEND_OPTIONS_SECURE - Message is sent over an encrypted channel
* @see #send(Member[], Serializable , int)
* @see #send(Member[], Serializable, int, ErrorHandler)
*/
int SEND_OPTIONS_SECURE = 0x0010;
/**
* Send options. When a message is sent with this flag on
* the system sends the message using UDP instead of TCP
* @see #send(Member[], Serializable , int)
* @see #send(Member[], Serializable, int, ErrorHandler)
*/
int SEND_OPTIONS_UDP = 0x0020;
/**
* 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 #send(Member[], Serializable , int)
* @see #send(Member[], Serializable, int, ErrorHandler)
*/
int SEND_OPTIONS_MULTICAST = 0x0040;
/**
* 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 #SEND_OPTIONS_USE_ACK
* @see #send(Member[], Serializable , int)
* @see #send(Member[], Serializable, int, ErrorHandler)
*/
int SEND_OPTIONS_DEFAULT = SEND_OPTIONS_USE_ACK;
/**
* Adds an interceptor to the channel message chain.
* @param interceptor ChannelInterceptor
*/
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
* 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.
*/
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
* 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.
*/
void stop(int svc) throws ChannelException;
/**
* Send a message to one or more members in the cluster
* @param 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.
* @param msg Serializable - the message to send, has to be serializable, or a ByteMessage 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
* @throws ChannelException if a serialization error happens.
* @see ByteMessage
* @see #SEND_OPTIONS_USE_ACK
* @see #SEND_OPTIONS_ASYNCHRONOUS
* @see #SEND_OPTIONS_SYNCHRONIZED_ACK
*/
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.
*/
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.
* 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)
*/
void heartbeat();
/**
* Enables or disables internal heartbeat.
* @param enable boolean - default value is implementation specific
* @see #heartbeat()
*/
void setHeartbeat(boolean enable);
/**
* 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
* @param listener MembershipListener
* @see MembershipListener
*/
void addMembershipListener(MembershipListener 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
* @param listener ChannelListener
* @see ChannelListener
* @see Heartbeat
*/
void addChannelListener(ChannelListener listener);
/**
* remove a membership listener, listeners are removed based on Object.hashCode and Object.equals
* @param listener MembershipListener
* @see MembershipListener
*/
void removeMembershipListener(MembershipListener listener);
/**
* remove a channel listener, listeners are removed based on Object.hashCode and Object.equals
* @param listener ChannelListener
* @see ChannelListener
*/
void removeChannelListener(ChannelListener listener);
/**
* Returns true if there are any members in the group,
* this call is the same as getMembers().length > 0
* @return boolean - true if there are any members automatically discovered
*/
boolean hasMembers() ;
/**
* Get all current group members
* @return all members or empty array, never null
*/
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
*/
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.
* In most cases, this is not necessary.
* @param mbr Member
* @return Member
*/
Member getMember(Member mbr);
/**
* Return the name of this channel.
* @return channel name
*/
String getName();
/**
* Set the name of this channel
* @param name The new channel name
*/
void setName(String name);
}
