org.jgroups
public class JChannel extends Channel
Properties
Properties are used to configure a channel, and are accepted in several forms; the String form is described here. A property string consists of a number of properties separated by colons. For example:
"<prop1>(arg1=val1):<prop2>(arg1=val1;arg2=val2):<prop3>:<propn>"
Each property relates directly to a protocol layer, which is implemented as a Java class. When a protocol stack is to be created based on the above property string, the first property becomes the bottom-most layer, the second one will be placed on the first, etc.: the stack is created from the bottom to the top, as the string is parsed from left to right. Each property has to be the name of a Java class that resides in the org.jgroups.protocols package.
Note that only the base name has to be given, not the fully specified class name (e.g., UDP instead of org.jgroups.protocols.UDP).
Each layer may have 0 or more arguments, which are specified as a list of name/value pairs in parentheses directly after the property. In the example above, the first protocol layer has 1 argument, the second 2, the third none. When a layer is created, these properties (if there are any) will be set in a layer by invoking the layer's setProperties() method
As an example the property string below instructs JGroups to create a JChannel with protocols UDP, PING, FD and GMS:
"UDP(mcast_addr=228.10.9.8;mcast_port=5678):PING:FD:GMS"
The UDP protocol layer is at the bottom of the stack, and it should use mcast address 228.10.9.8. and port 5678 rather than the default IP multicast address and port. The only other argument instructs FD to output debug information while executing. Property UDP refers to a class UDP, which is subsequently loaded and an instance of which is created as protocol layer. If any of these classes are not found, an exception will be thrown and the construction of the stack will be aborted.
Version: $Revision: 1.45.2.1 $
Field Summary | |
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protected JChannel.CloserThread | closer Thread responsible for closing a channel and potentially reconnecting to it (e.g., when shunned). |
static String | DEFAULT_PROTOCOL_STACK
The default protocol stack used by the default constructor. |
protected Log | log |
protected long | received_bytes |
protected long | received_msgs |
protected long | sent_bytes |
protected long | sent_msgs |
protected boolean | stats Collect statistics |
Constructor Summary | |
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JChannel()
Constructs a JChannel instance with the protocol stack
specified by the DEFAULT_PROTOCOL_STACK member.
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JChannel(File properties)
Constructs a JChannel instance with the protocol stack
configuration contained by the specified file.
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JChannel(Element properties)
Constructs a JChannel instance with the protocol stack
configuration contained by the specified XML element.
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JChannel(URL properties)
Constructs a JChannel instance with the protocol stack
configuration indicated by the specified URL.
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JChannel(String properties)
Constructs a JChannel instance with the protocol stack
configuration based upon the specified properties parameter.
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protected | JChannel(ProtocolStackConfigurator configurator)
Constructs a JChannel instance with the protocol stack
configuration contained by the protocol stack configurator parameter.
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JChannel(Object properties)
Creates a new JChannel with the protocol stack as defined in the properties
parameter. an example of this parameter is "UDP:PING:FD:STABLE:NAKACK:UNICAST:FRAG:FLUSH:GMS:VIEW_ENFORCER:STATE_TRANSFER:QUEUE" Other examples can be found in the ./conf directory |
Method Summary | |
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void | blockOk()
Called to acknowledge a block() (callback in MembershipListener or
BlockEvent received from call to receive() ).
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void | close()
Destroys the channel.
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void | connect(String channel_name)
Connects the channel to a group.
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void | disconnect()
Disconnects the channel if it is connected. |
void | down(Event evt)
Sends a message through the protocol stack if the stack is available |
String | dumpQueue() |
Map | dumpStats()
Returns a map of statistics of the various protocols and of the channel itself. |
String | dumpTimerQueue() |
void | enableStats(boolean stats) |
boolean | getAllStates(Vector targets, long timeout)
Retrieves the current group state. |
String | getChannelName()
returns the name of the channel
if the channel is not connected or if it is closed it will return null |
Address | getLocalAddress()
returns the local address of the channel
returns null if the channel is closed |
protected Log | getLog() |
int | getNumberOfTasksInTimer() |
int | getNumMessages() |
Object | getOpt(int option)
returns the value of an option. |
String | getProperties()
returns the protocol stack configuration in string format.
an example of this property is "UDP:PING:FD:STABLE:NAKACK:UNICAST:FRAG:FLUSH:GMS:VIEW_ENFORCER:STATE_TRANSFER:QUEUE" |
ProtocolStack | getProtocolStack()
Returns the protocol stack.
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long | getReceivedBytes() |
long | getReceivedMessages() |
long | getSentBytes() |
long | getSentMessages() |
boolean | getState(Address target, long timeout)
Retrieves the current group state. |
View | getView()
Returns the current view.
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boolean | isConnected()
returns true if the Connect operation has been called successfully |
boolean | isOpen()
returns true if the Open operation has been called successfully |
boolean | isSuspended() |
void | open()
Opens the channel.
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Object | peek(long timeout)
Just peeks at the next message, view or block. |
String | printProtocolSpec(boolean include_properties)
Returns a pretty-printed form of all the protocols. |
Object | receive(long timeout)
Blocking receive method.
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void | resetStats() |
void | resume() Send() unblocks |
void | returnState(byte[] state)
Called by the application is response to receiving a getState() object when
calling receive() .
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void | send(Message msg)
Sends a message through the protocol stack.
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void | send(Address dst, Address src, Serializable obj)
creates a new message with the destination address, and the source address
and the object as the message value |
void | setOpt(int option, Object value)
Sets a channel option. |
void | shutdown() Shuts down the channel without disconnecting |
boolean | statsEnabled() |
void | suspend() Send() blocks from now on, until resume() is called |
String | toString(boolean details) |
void | up(Event evt)
Callback method Called by the ProtocolStack when a message is received. |
JChannel
instance with the protocol stack
specified by the DEFAULT_PROTOCOL_STACK
member.
Throws: ChannelException if problems occur during the initialization of the protocol stack.
JChannel
instance with the protocol stack
configuration contained by the specified file.
Parameters: properties a file containing a JGroups XML protocol stack configuration.
Throws: ChannelException if problems occur during the configuration or initialization of the protocol stack.
JChannel
instance with the protocol stack
configuration contained by the specified XML element.
Parameters: properties a XML element containing a JGroups XML protocol stack configuration.
Throws: ChannelException if problems occur during the configuration or initialization of the protocol stack.
JChannel
instance with the protocol stack
configuration indicated by the specified URL.
Parameters: properties a URL pointing to a JGroups XML protocol stack configuration.
Throws: ChannelException if problems occur during the configuration or initialization of the protocol stack.
JChannel
instance with the protocol stack
configuration based upon the specified properties parameter.
Parameters: properties an old style property string, a string representing a system resource containing a JGroups XML configuration, a string representing a URL pointing to a JGroups XML XML configuration, or a string representing a file name that contains a JGroups XML configuration.
Throws: ChannelException if problems occur during the configuration and initialization of the protocol stack.
JChannel
instance with the protocol stack
configuration contained by the protocol stack configurator parameter.
All of the public constructors of this class eventually delegate to this method.
Parameters: configurator a protocol stack configurator containing a JGroups protocol stack configuration.
Throws: ChannelException if problems occur during the initialization of the protocol stack.
Deprecated: Use the constructors with specific parameter types instead.
Creates a new JChannel with the protocol stack as defined in the properties parameter. an example of this parameter isParameters: properties the protocol stack setup; if null, the default protocol stack will be used. The properties can also be a java.net.URL object or a string that is a URL spec. The JChannel will validate any URL object and String object to see if they are a URL. In case of the parameter being a url, the JChannel will try to load the xml from there. In case properties is a org.w3c.dom.Element, the ConfiguratorFactory will parse the DOM tree with the element as its root element.
MembershipListener
or
BlockEvent
received from call to receive()
).
After sending blockOk(), no messages should be sent until a new view has been received.
Calling this method on a closed channel has no effect.Parameters: channel_name A String
denoting the group name. Cannot be null.
Throws: ChannelException The protocol stack cannot be started ChannelClosedException The channel is closed and therefore cannot be used any longer. A new channel has to be created first.
Parameters: evt the message to send down, encapsulated in an event
Returns: Map
timeout
milliseconds have elapsed. The argument of GET_STATE_OK should be a vector of objects.Parameters: targets - the target members to receive the state from ( an Address list ) timeout - the number of milliseconds to wait for the operation to complete successfully
Returns: true of the state was received, false if the operation timed out
Parameters: option the option you want to see the value for
Returns: the object value, in most cases java.lang.Boolean
See Also: JChannel
timeout
milliseconds have elapsed. The argument of GET_STATE_OK should be a single object.Parameters: target - the target member to receive the state from. if null, state is retrieved from coordinator timeout - the number of milliseconds to wait for the operation to complete successfully
Returns: true of the state was received, false if the operation timed out
Returns: returns the current group view, or null if the channel is closed or disconnected
Parameters: timeout the number of milliseconds to wait if the receive queue is empty. 0 means wait forever
Throws: TimeoutException if a timeout occured prior to a new message was received ChannelNotConnectedException ChannelClosedException
See Also: JChannel
getState()
object when
calling receive()
.
When the application receives a getState() message on the receive() method,
it should call returnState() to reply with the state of the applicationParameters: state The state of the application as a byte buffer (to send over the network).
Parameters: msg the message to be sent through the protocol stack, the destination of the message is specified inside the message itself
Throws: ChannelNotConnectedException ChannelClosedException
Parameters: dst - the destination address of the message, null for all members src - the source address of the message obj - the value of the message
Throws: ChannelNotConnectedException ChannelClosedException
See Also: JChannel
There are certain dependencies between the options that you can set, I will try to describe them here.
Option: Channel.VIEW option
Value: java.lang.Boolean
Result: set to true the JChannel will receive VIEW change events
Option: Channel.SUSPECT
Value: java.lang.Boolean
Result: set to true the JChannel will receive SUSPECT events
Option: Channel.BLOCK
Value: java.lang.Boolean
Result: set to true will set setOpt(VIEW, true) and the JChannel will receive BLOCKS and VIEW events
Option: GET_STATE_EVENTS
Value: java.lang.Boolean
Result: set to true the JChannel will receive state events
Option: LOCAL
Value: java.lang.Boolean
Result: set to true the JChannel will receive messages that it self sent out.
Option: AUTO_RECONNECT
Value: java.lang.Boolean
Result: set to true and the JChannel will try to reconnect when it is being closed
Option: AUTO_GETSTATE
Value: java.lang.Boolean
Result: set to true, the AUTO_RECONNECT will be set to true and the JChannel will try to get the state after a close and reconnect happens
Parameters: option the parameter option Channel.VIEW, Channel.SUSPECT, etc value the value to set for this option
Receive
s will dequeue it.Parameters: evt the event carrying the message from the protocol stack