org.jgroups
public abstract class Channel extends Object
Receiver
in setReceiver(Receiver)
and implementing the
MessageListener.receive(Message)
callback.
A channel instance is created using the public constructor.
Various degrees of sophistication in message exchange can be achieved using building blocks on top of channels; e.g., light-weight groups, synchronous message invocation, or remote method calls. Channels are on the same abstraction level as sockets, and should really be simple to use. Higher-level abstractions are all built on top of channels.DatagramPacket
,
MulticastSocket
,
JChannel
Modifier and Type | Class and Description |
---|---|
static class |
Channel.State |
Modifier and Type | Field and Description |
---|---|
protected Set<ChannelListener> |
channel_listeners |
protected boolean |
discard_own_messages |
protected Receiver |
receiver |
protected SocketFactory |
socket_factory |
protected Channel.State |
state
The current state of the channel
|
protected UpHandler |
up_handler |
Constructor and Description |
---|
Channel() |
Modifier and Type | Method and Description |
---|---|
void |
addChannelListener(ChannelListener listener)
Adds a ChannelListener instance that will be notified when a channel event such as connect,
disconnect or close occurs.
|
void |
clearChannelListeners()
Clears all installed ChannelListener instances
|
abstract void |
close()
Destroys the channel and its associated resources (e.g., the protocol stack).
|
abstract void |
connect(String cluster_name)
Connects the channel to a group.
|
abstract void |
connect(String cluster_name,
Address target,
long timeout)
Connects this channel to a group and gets a state from a specified state provider.
|
abstract void |
disconnect()
Disconnects the channel if it is connected.
|
Object |
down(Event evt)
Enables access to event mechanism of a channel and is normally not used by clients directly.
|
abstract Map<String,Object> |
dumpStats()
Returns a map of statistics of the various protocols and of the channel itself.
|
abstract boolean |
flushSupported() |
abstract Address |
getAddress()
Returns the channel's own address.
|
abstract String |
getClusterName()
Returns the cluster name of the group of which the channel is a member.
|
boolean |
getDiscardOwnMessages()
Returns true if this channel will discard its own messages, false otherwise
|
protected abstract Log |
getLog() |
abstract String |
getName()
Returns the logical name of this channel if set.
|
abstract String |
getName(Address member)
Returns the logical name of a given member.
|
String |
getProperties() |
abstract ProtocolStack |
getProtocolStack() |
Receiver |
getReceiver()
Returns a receiver for this channel if it has been installed using
setReceiver(Receiver) , null otherwise |
SocketFactory |
getSocketFactory() |
String |
getState() |
abstract void |
getState(Address target,
long timeout)
Retrieves the full state from the target member.
|
UpHandler |
getUpHandler()
Returns UpHandler installed for this channel
|
abstract View |
getView()
Gets the current view.
|
boolean |
isClosed()
Determines whether the channel is in the closed state.
|
boolean |
isConnected()
Determines whether the channel is connected to a group.
|
boolean |
isConnecting()
Determines whether the channel is in the connecting state; this means
connect(String) has been
called, but hasn't returned yet |
boolean |
isOpen()
Determines whether the channel is open; ie.
|
protected void |
notifyChannelClosed(Channel c) |
protected void |
notifyChannelConnected(Channel c) |
protected void |
notifyChannelDisconnected(Channel c) |
void |
removeChannelListener(ChannelListener listener)
Removes a ChannelListener previously installed
|
abstract void |
send(Address dst,
byte[] buf)
Sends a message.
|
abstract void |
send(Address dst,
byte[] buf,
int offset,
int length)
Sends a message to a destination.
|
abstract void |
send(Address dst,
Object obj)
Helper method to create a Message with given parameters and invoke
send(Message) . |
abstract void |
send(Message msg)
Sends a message.
|
void |
setDiscardOwnMessages(boolean flag)
When set to true, all messages sent by a member A will be discarded by A.
|
abstract void |
setName(String name)
Sets the logical name for the channel.
|
void |
setReceiver(Receiver r)
Sets the receiver for this channel.
|
void |
setSocketFactory(SocketFactory factory) |
void |
setUpHandler(UpHandler up_handler)
Sets this channel event handler to be a recipient off all events .
|
abstract void |
startFlush(boolean automatic_resume)
Will perform a flush of the system, ie.
|
abstract void |
startFlush(List<Address> flushParticipants,
boolean automatic_resume)
Performs a partial flush in a cluster for flush participants.
|
abstract void |
stopFlush() |
abstract void |
stopFlush(List<Address> flushParticipants) |
protected volatile Channel.State state
protected UpHandler up_handler
protected Set<ChannelListener> channel_listeners
protected Receiver receiver
protected SocketFactory socket_factory
protected boolean discard_own_messages
public String getState()
protected abstract Log getLog()
public abstract ProtocolStack getProtocolStack()
public SocketFactory getSocketFactory()
public void setSocketFactory(SocketFactory factory)
public abstract void connect(String cluster_name) throws Exception
All channels with the same name form a group, that means all messages sent to the group will be received by all channels connected to the same cluster name.
cluster_name
- The name of the channel to connect to.Exception
- The protocol stack cannot be startedIllegalStateException
- The channel is closedpublic abstract void connect(String cluster_name, Address target, long timeout) throws Exception
connect and getState methods successively.
If FLUSH protocol is in channel's stack definition only one flush is executed for both connecting and
fetching state rather than two flushes if we invoke connect and getState in succession.
If the channel is closed an exception will be thrown.
cluster_name
- the cluster name to connect to. Cannot be null.target
- the state provider. If null state will be fetched from coordinator, unless this channel is coordinator.timeout
- the timeout for state transfer.Exception
- Connecting to the cluster or state transfer was not successfulIllegalStateException
- The channel is closed and therefore cannot be usedpublic abstract void disconnect()
connect(String)
public abstract void close()
ChannelClosed
exception (or
results in a null operation). It is a null operation if the channel is already closed.
If the channel is connected to a group, disconnect()
will be called first.
public boolean isOpen()
public boolean isConnected()
public boolean isConnecting()
connect(String)
has been
called, but hasn't returned yetpublic boolean isClosed()
public abstract Map<String,Object> dumpStats()
public abstract void send(Message msg) throws Exception
null
address sends the message to all
group members.
msg
- The message to be sent. Destination and buffer should be set. A null destination
means to send to all group members.IllegalStateException
- thrown if the channel is disconnected or closedException
public abstract void send(Address dst, Object obj) throws Exception
send(Message)
.dst
- Destination address for message. If null, message will be sent to all current group
membersobj
- A serializable object. Will be marshalled into the byte buffer of the Message. If it
is not serializable, an exception will be thrownException
- exception thrown if message sending was not successfulpublic abstract void send(Address dst, byte[] buf) throws Exception
send(Address,byte[],int,int)
for detailsdst
- destination address for message. If null, message will be sent to all current group
membersbuf
- buffer message payloadException
- exception thrown if message sending was not successfulpublic abstract void send(Address dst, byte[] buf, int offset, int length) throws Exception
dst
- The destination address. If null, the message will be sent to all cluster nodes (=
group members)buf
- The buffer to be sentoffset
- The offset into the bufferlength
- The length of the data to be sent. Has to be <= buf.length - offset. This will send
length
bytes starting at offset
Exception
- If send() failedpublic Object down(Event evt)
sends
- an Event to a specific protocol layer and receive a response.public abstract View getView()
connect()
. The result of calling this method on an unconnected channel is
implementation defined (may return null). Calling this method on a closed channel returns a
null view.public abstract Address getAddress()
send()
operation.public abstract String getName()
public abstract String getName(Address member)
member
- member
public abstract void setName(String name)
name
- public abstract String getClusterName()
connect()
. Calling this method on a closed channel
returns null
.public String getProperties()
public void setUpHandler(UpHandler up_handler)
the
- handler to handle channel eventspublic UpHandler getUpHandler()
public void addChannelListener(ChannelListener listener)
listener
- to be notifiedpublic void removeChannelListener(ChannelListener listener)
listener
- to be removedpublic void clearChannelListeners()
public void setReceiver(Receiver r)
r
- the receiver instance for this channelReceiver
public Receiver getReceiver()
setReceiver(Receiver)
, null otherwisepublic void setDiscardOwnMessages(boolean flag)
flag
- public boolean getDiscardOwnMessages()
public abstract boolean flushSupported()
public abstract void startFlush(List<Address> flushParticipants, boolean automatic_resume) throws Exception
automatic_resume
- if true call stopFlush()
after the flushException
startFlush(boolean)
public abstract void startFlush(boolean automatic_resume) throws Exception
stopFlush()
is called.
In case of flush collisions, a random sleep time backoff algorithm is employed and the flush
is reattempted for numberOfAttempts. Therefore this method is guaranteed to return after
timeout x numberOfAttempts milliseconds.automatic_resume
- if true call stopFlush()
after the flushException
public abstract void stopFlush()
public abstract void getState(Address target, long timeout) throws Exception
State transfer is initiated by invoking getState on this channel. The state provider in turn
invokes MessageListener.getState(java.io.OutputStream)
callback and sends a state to
this node, the state receiver. After the state arrives to the state receiver
MessageListener.setState(java.io.InputStream)
callback is invoked to install the
state.
target
- The state provider. If null the coordinator is used by defaulttimeout
- The number of milliseconds to wait for the operation to complete successfully. 0
waits until the state has been receivedIllegalStateException
- The channel was closed or disconnected, or the flush (if present) failedStateTransferException
- raised if there was a problem during the state transferException
MessageListener.getState(java.io.OutputStream)
,
MessageListener.setState(java.io.InputStream)
protected void notifyChannelConnected(Channel c)
protected void notifyChannelDisconnected(Channel c)
protected void notifyChannelClosed(Channel c)
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