org.jgroups.blocks
Class RequestCorrelator
java.lang.Object
org.jgroups.blocks.RequestCorrelator
public class RequestCorrelator
extends java.lang.Object
Framework to send requests and receive matching responses (matching on
request ID).
Multiple requests can be sent at a time. Whenever a response is received,
the correct
RspCollector
is looked up (key = id) and its
method
receiveResponse()
invoked. A caller may use
done()
to signal that no more responses are expected, and that
the corresponding entry may be removed.
RequestCorrelator
can be installed at both client and server
sides, it can also switch roles dynamically; i.e., send a request and at
the same time process an incoming request (when local delivery is enabled,
this is actually the default).
protected java.util.Stack | call_stack - This field is used only if deadlock detection is enabled.
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protected boolean | concurrent_processing - Process items on the queue concurrently (Scheduler).
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protected boolean | deadlock_detection - Whether or not to perform deadlock detection for synchronous (potentially recursive) group method invocations.
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protected Address | local_addr - The address of this group member
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protected static Log | log
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protected String | name - makes the instance unique (together with IDs)
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protected RequestHandler | request_handler - The handler for the incoming requests.
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protected Map | requests - The table of pending requests (keys=Long (request IDs), values=RequestEntry)
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protected Scheduler | scheduler - The dispatching thread pool
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protected boolean | started
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protected Object | transport - The protocol layer to use to pass up/down messages.
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RequestCorrelator(String name, Object transport, RequestHandler handler) - Constructor.
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RequestCorrelator(String name, Object transport, RequestHandler handler, boolean deadlock_detection) - Constructor.
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RequestCorrelator(String name, Object transport, RequestHandler handler, boolean deadlock_detection, boolean concurrent_processing)
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RequestCorrelator(String name, Object transport, RequestHandler handler, boolean deadlock_detection, Address local_addr)
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RequestCorrelator(String name, Object transport, RequestHandler handler, boolean deadlock_detection, Address local_addr, boolean concurrent_processing)
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RequestCorrelator(String name, Object transport, RequestHandler handler, Address local_addr)
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call_stack
protected java.util.Stack call_stack
This field is used only if deadlock detection is enabled.
In case of nested synchronous requests, it holds a list of the
addreses of the senders with the address at the bottom being the
address of the first caller
concurrent_processing
protected boolean concurrent_processing
Process items on the queue concurrently (Scheduler). The default is to wait until the processing of an item
has completed before fetching the next item from the queue. Note that setting this to true
may destroy the properties of a protocol stack, e.g total or causal order may not be
guaranteed. Set this to true only if you know what you're doing !
deadlock_detection
protected boolean deadlock_detection
Whether or not to perform deadlock detection for synchronous (potentially recursive) group method invocations.
If on, we use a scheduler (handling a priority queue), otherwise we don't and call handleRequest() directly.
local_addr
protected Address local_addr
The address of this group member
log
protected static final Log log
name
protected String name
makes the instance unique (together with IDs)
request_handler
protected RequestHandler request_handler
The handler for the incoming requests. It is called from inside the
dispatcher thread
requests
protected final Map requests
The table of pending requests (keys=Long (request IDs), values=RequestEntry)
scheduler
protected Scheduler scheduler
The dispatching thread pool
started
protected boolean started
transport
protected Object transport
The protocol layer to use to pass up/down messages. Can be either a Protocol or a Transport
RequestCorrelator
public RequestCorrelator(String name,
Object transport,
RequestHandler handler)
Constructor. Uses transport to send messages. If handler
is not null, all incoming requests will be dispatched to it (via
handle(Message)
).
name
- Used to differentiate between different RequestCorrelators
(e.g. in different protocol layers). Has to be unique if multiple
request correlators are used.transport
- Used to send/pass up requests. Can be either a Transport (only send() will be
used then), or a Protocol (passUp()/passDown() will be used)handler
- Request handler. Method handle(Message)
will be called when a request is received.
RequestCorrelator
public RequestCorrelator(String name,
Object transport,
RequestHandler handler,
boolean deadlock_detection)
Constructor. Uses transport to send messages. If handler
is not null, all incoming requests will be dispatched to it (via
handle(Message)
).
name
- Used to differentiate between different RequestCorrelators
(e.g. in different protocol layers). Has to be unique if multiple
request correlators are used.transport
- Used to send/pass up requests. Can be either a Transport (only send() will be
used then), or a Protocol (passUp()/passDown() will be used)handler
- Request handler. Method handle(Message)
will be called when a request is received.deadlock_detection
- When enabled (true) recursive synchronous
message calls will be detected and processed with higher priority in
order to solve deadlocks. Slows down processing a little bit when
enabled due to runtime checks involved.
RequestCorrelator
public RequestCorrelator(String name,
Object transport,
RequestHandler handler,
boolean deadlock_detection,
boolean concurrent_processing)
RequestCorrelator
public RequestCorrelator(String name,
Object transport,
RequestHandler handler,
boolean deadlock_detection,
Address local_addr)
RequestCorrelator
public RequestCorrelator(String name,
Object transport,
RequestHandler handler,
boolean deadlock_detection,
Address local_addr,
boolean concurrent_processing)
RequestCorrelator
public RequestCorrelator(String name,
Object transport,
RequestHandler handler,
Address local_addr)
done
public void done(long id)
Used to signal that a certain request may be garbage collected as
all responses have been received.
getLocalAddress
public Address getLocalAddress()
receive
public void receive(Event evt)
Callback.
Called by the protocol below when a message has been received. The
algorithm should test whether the message is destined for us and,
if not, pass it up to the next layer. Otherwise, it should remove
the header and check whether the message is a request or response.
In the first case, the message will be delivered to the request
handler registered (calling its
handle()
method), in the
second case, the corresponding response collector is looked up and
the message delivered.
receiveMessage
public boolean receiveMessage(Message msg)
Handles a message coming from a layer below
- true if the event should be forwarded further up, otherwise false (message was consumed)
receiveSuspect
public void receiveSuspect(Address mbr)
Event.SUSPECT event received from a layer below.
All response collectors currently registered will
be notified that
mbr
may have crashed, so they won't
wait for its response.
receiveView
public void receiveView(View new_view)
Event.VIEW_CHANGE event received from a layer below.
Mark all responses from members that are not in new_view as
NOT_RECEIVED.
sendRequest
public void sendRequest(long id,
List dest_mbrs,
Message msg,
RspCollector coll)
Send a request to a group. If no response collector is given, no
responses are expected (making the call asynchronous).
id
- The request ID. Must be unique for this JVM (e.g. current
time in millisecs)dest_mbrs
- The list of members who should receive the call. Usually a group RPC
is sent via multicast, but a receiver drops the request if its own address
is not in this list. Will not be used if it is null.msg
- The request to be sent. The body of the message carries
the request datacoll
- A response collector (usually the object that invokes
this method). Its methods receiveResponse()
and
suspect()
will be invoked when a message has been received
or a member is suspected, respectively.
setConcurrentProcessing
public void setConcurrentProcessing(boolean concurrent_processing)
setDeadlockDetection
public void setDeadlockDetection(boolean flag)
Switch the deadlock detection mechanism on/off
flag
- the deadlock detection flag
setLocalAddress
public void setLocalAddress(Address local_addr)
setRequestHandler
public void setRequestHandler(RequestHandler handler)
Copyright B) 1998-2005 Bela Ban. All Rights Reserved.