Class GroupRequest
- java.lang.Object
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- org.jgroups.blocks.GroupRequest
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- All Implemented Interfaces:
RspCollector
,Command
public class GroupRequest extends java.lang.Object implements RspCollector, Command
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 theexecute()
method and callreceiveResponse()
to do so.Requirements: lossless delivery, e.g. acknowledgment-based message confirmation.
- Version:
- $Id: GroupRequest.java,v 1.30.2.3 2008/11/17 13:37:59 belaban Exp $
- Author:
- Bela Ban
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Field Summary
Fields Modifier and Type Field Description protected RequestCorrelator
corr
protected boolean
done
protected int
expected_mbrs
static int
GET_ABS_MAJORITY
return majority (of all members, may block)static int
GET_ALL
return all responsesstatic int
GET_FIRST
return only first responsestatic int
GET_MAJORITY
return majority (of all non-faulty members)static int
GET_N
return n responses (may block)static int
GET_NONE
return no response (async call)protected Message
request_msg
protected RspFilter
rsp_filter
protected int
rsp_mode
protected long
timeout
protected Transport
transport
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Constructor Summary
Constructors Constructor Description GroupRequest(Message m, RequestCorrelator corr, java.util.Vector<Address> members, int rsp_mode)
GroupRequest(Message m, RequestCorrelator corr, java.util.Vector<Address> members, int rsp_mode, long timeout, int expected_mbrs)
GroupRequest(Message m, Transport transport, java.util.Vector<Address> members, int rsp_mode)
GroupRequest(Message m, Transport transport, java.util.Vector<Address> members, int rsp_mode, long timeout, int expected_mbrs)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
execute()
boolean
execute(boolean use_anycasting)
Sends the message.Address
getCaller()
int
getNumSuspects()
RspList
getResults()
Returns the results as a RspListjava.util.Vector<Address>
getSuspects()
Returns the list of suspected members.boolean
isDone()
void
receiveResponse(java.lang.Object response_value, Address sender)
Callback (called by RequestCorrelator or Transport).void
reset(java.util.Vector<Address> mbrs)
This method sets themembership
variable to the value ofmembers
.void
setCaller(Address caller)
void
setResponseFilter(RspFilter filter)
void
suspect(Address suspected_member)
Callback (called by RequestCorrelator or Transport).java.lang.String
toString()
void
viewChange(View new_view)
Any member of 'membership' that is not in the new view is flagged as SUSPECTED.
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Field Detail
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GET_FIRST
public static final int GET_FIRST
return only first response- See Also:
- Constant Field Values
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GET_ALL
public static final int GET_ALL
return all responses- See Also:
- Constant Field Values
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GET_MAJORITY
public static final int GET_MAJORITY
return majority (of all non-faulty members)- See Also:
- Constant Field Values
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GET_ABS_MAJORITY
public static final int GET_ABS_MAJORITY
return majority (of all members, may block)- See Also:
- Constant Field Values
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GET_N
public static final int GET_N
return n responses (may block)- See Also:
- Constant Field Values
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GET_NONE
public static final int GET_NONE
return no response (async call)- See Also:
- Constant Field Values
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request_msg
protected final Message request_msg
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corr
protected final RequestCorrelator corr
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transport
protected Transport transport
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rsp_filter
protected RspFilter rsp_filter
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rsp_mode
protected int rsp_mode
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done
protected boolean done
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timeout
protected long timeout
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expected_mbrs
protected int expected_mbrs
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Constructor Detail
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GroupRequest
public GroupRequest(Message m, RequestCorrelator corr, java.util.Vector<Address> members, int rsp_mode)
- Parameters:
m
- The message to be sentcorr
- 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 reasonGroupRequest
uses it instead of aTransport
is that multiple requests/responses might be sent/received concurrently.members
- The initial membership. This value reflects the membership to which the request is sent (and from which potential responses are expected). Is reset by reset().rsp_mode
- How many responses are expected. Can beGET_ALL
: wait for all responses from non-suspected members. A suspicion service might warn us when a member from which a response is outstanding has crashed, so it can be excluded from the responses. If no suspision service is available, a timeout can be used (a value of 0 means wait forever). If a timeout of 0 is used, no suspicion service is available and a member from which we expect a response has crashed, this methods blocks forever !.GET_FIRST
: wait for the first available response.GET_MAJORITY
: wait for the majority of all responses. The majority is re-computed when a member is suspected.GET_ABS_MAJORITY
: wait for the majority of all members. This includes failed members, so it may block if no timeout is specified.GET_N
: wait for N members. Return if n is >= membership+suspects.GET_NONE
: don't wait for any response. Essentially send an asynchronous message to the group members.
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GroupRequest
public GroupRequest(Message m, RequestCorrelator corr, java.util.Vector<Address> members, int rsp_mode, long timeout, int expected_mbrs)
- Parameters:
timeout
- Time to wait for responses (ms). A value of <= 0 means wait indefinitely (e.g. if a suspicion service is available; timeouts are not needed).
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GroupRequest
public GroupRequest(Message m, Transport transport, java.util.Vector<Address> members, int rsp_mode)
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GroupRequest
public GroupRequest(Message m, Transport transport, java.util.Vector<Address> members, int rsp_mode, long timeout, int expected_mbrs)
- Parameters:
timeout
- Time to wait for responses (ms). A value of <= 0 means wait indefinitely (e.g. if a suspicion service is available; timeouts are not needed).
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Method Detail
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getCaller
public Address getCaller()
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setCaller
public void setCaller(Address caller)
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setResponseFilter
public void setResponseFilter(RspFilter filter)
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execute
public boolean execute() throws java.lang.Exception
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execute
public boolean execute(boolean use_anycasting) throws java.lang.Exception
Sends the message. Returns when n responses have been received, or a timeout has occurred. n can be the first response, all responses, or a majority of the responses.- Throws:
java.lang.Exception
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reset
public final void reset(java.util.Vector<Address> mbrs)
This method sets themembership
variable to the value ofmembers
. It requires that the caller already hold thersp_mutex
lock.- Parameters:
mbrs
- The new list of members
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receiveResponse
public void receiveResponse(java.lang.Object response_value, Address sender)
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 interfaceRspCollector
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suspect
public void suspect(Address suspected_member)
Callback (called by RequestCorrelator or Transport). Report toGroupRequest
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 interfaceRspCollector
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viewChange
public void viewChange(View new_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 interfaceRspCollector
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getResults
public RspList getResults()
Returns the results as a RspList
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toString
public java.lang.String toString()
- Overrides:
toString
in classjava.lang.Object
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getNumSuspects
public int getNumSuspects()
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getSuspects
public java.util.Vector<Address> getSuspects()
Returns the list of suspected members. An attempt to modify the return value will throw an excxeption
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isDone
public boolean isDone()
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