org.jgroups.blocks

Class GroupRequest<T>

java.lang.Object

org.jgroups.blocks.Request

org.jgroups.blocks.GroupRequest<T>

All Implemented Interfaces:

java.util.concurrent.Future, Condition, NotifyingFuture

public class GroupRequest<T>
extends Request

Sends a message to all members of the group and waits for all responses (or timeout). Returns a boolean value (success or failure). Results (if any) can be retrieved when done.

The supported transport to send requests is currently either a RequestCorrelator or a generic Transport. One of them has to be given in the constructor. It will then be used to send a request. When a message is received by either one, the receiveResponse() of this class has to be called (this class does not actively receive requests/responses itself). Also, when a view change or suspicion is received, the methods viewChange() or suspect() of this class have to be called.

When started, an array of responses, correlating to the membership, is created. Each response is added to the corresponding field in the array. When all fields have been set, the algorithm terminates. This algorithm can optionally use a suspicion service (failure detector) to detect (and exclude from the membership) fauly members. If no suspicion service is available, timeouts can be used instead (see execute()). When done, a list of suspected members can be retrieved.

Because a channel might deliver requests, and responses to different requests, the GroupRequest class cannot itself receive and process requests/responses from the channel. A mechanism outside this class has to do this; it has to determine what the responses are for the message sent by the execute() method and call receiveResponse() to do so.

Author:

Bela Ban

Field Summary

Fields

Modifier and Type	Field and Description
protected java.util.Map<Address,Rsp<T>>	requests Correlates requests and responses

Fields inherited from class org.jgroups.blocks.Request

cond, corr, done, listener, lock, log, options, req_id, start_time

Constructor Summary

Constructors

Constructor and Description
GroupRequest(RequestCorrelator corr, java.util.Collection<Address> targets, RequestOptions options)

Method Summary

Modifier and Type	Method and Description
RspList<T>	get()
RspList<T>	get(long timeout, java.util.concurrent.TimeUnit unit)
RspList<T>	getResults() Returns the results as a RspList
void	receiveResponse(java.lang.Object response_value, Address sender, boolean is_exception) Callback (called by RequestCorrelator or Transport).
protected boolean	responsesComplete()
void	sendRequest(Message req)
void	siteUnreachable(java.lang.String site)
void	suspect(Address suspected_member) Callback (called by RequestCorrelator or Transport).
java.lang.String	toString()
void	transportClosed() Marks all responses with an exception (unless a response was already marked as done)
void	viewChange(View view) Any member of 'membership' that is not in the new view is flagged as SUSPECTED.

Methods inherited from class org.jgroups.blocks.Request

cancel, checkCompletion, corrDone, execute, getResponsesComplete, isCancelled, isDone, isMet, requestId, requestId, responsesComplete, setListener, setResponseFilter, waitForResults

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

requests

protected final java.util.Map<Address,Rsp<T>> requests

Correlates requests and responses

Constructor Detail

GroupRequest

public GroupRequest(RequestCorrelator corr,
                    java.util.Collection<Address> targets,
                    RequestOptions options)

Parameters:

corr - The request correlator to be used. A request correlator sends requests tagged with a unique ID and notifies the sender when matching responses are received. The reason GroupRequest uses it instead of a Transport is that multiple requests/responses might be sent/received concurrently

targets - The targets, which are supposed to receive the message. Any receiver not in this set will discard the message. Targets are always a subset of the current membership

options - The request options to be used for this call

Method Detail

sendRequest

public void sendRequest(Message req)
                 throws java.lang.Exception

Specified by:

sendRequest in class Request

Throws:

java.lang.Exception

receiveResponse

public void receiveResponse(java.lang.Object response_value,
                            Address sender,
                            boolean is_exception)

Callback (called by RequestCorrelator or Transport). Adds a response to the response table. When all responses have been received, execute() returns.

Specified by:

receiveResponse in class Request

suspect

public void suspect(Address suspected_member)

Callback (called by RequestCorrelator or Transport). Report to GroupRequest that a member is reported as faulty (suspected). This method would probably be called when getting a suspect message from a failure detector (where available). It is used to exclude faulty members from the response list.

Specified by:

suspect in class Request

siteUnreachable

public void siteUnreachable(java.lang.String site)

Specified by:

siteUnreachable in class Request

viewChange

public void viewChange(View view)

Any member of 'membership' that is not in the new view is flagged as SUSPECTED. Any member in the new view that is not in the membership (ie, the set of responses expected for the current RPC) will not be added to it. If we did this we might run into the following problem:

• Membership is {A,B}
• A sends a synchronous group RPC (which sleeps for 60 secs in the invocation handler)
• C joins while A waits for responses from A and B
• If this would generate a new view {A,B,C} and if this expanded the response set to {A,B,C}, A would wait forever on C's response because C never received the request in the first place, therefore won't send a response.

Specified by:

viewChange in class Request

transportClosed

public void transportClosed()

Marks all responses with an exception (unless a response was already marked as done)

Specified by:

transportClosed in class Request

getResults

public RspList<T> getResults()

Returns the results as a RspList

get

public RspList<T> get()
               throws java.lang.InterruptedException,
                      java.util.concurrent.ExecutionException

Throws:

java.lang.InterruptedException

java.util.concurrent.ExecutionException

get

public RspList<T> get(long timeout,
                      java.util.concurrent.TimeUnit unit)
               throws java.lang.InterruptedException,
                      java.util.concurrent.ExecutionException,
                      java.util.concurrent.TimeoutException

Throws:

java.lang.InterruptedException

java.util.concurrent.ExecutionException

java.util.concurrent.TimeoutException

toString

public java.lang.String toString()

Overrides:

toString in class Request

responsesComplete

protected boolean responsesComplete()

Specified by:

responsesComplete in class Request