com.hazelcast.spi.impl.operationservice.impl

Class CallIdSequence

java.lang.Object

com.hazelcast.spi.impl.operationservice.impl.CallIdSequence

Direct Known Subclasses:

CallIdSequence.CallIdSequenceWithBackpressure, CallIdSequence.CallIdSequenceWithoutBackpressure

public abstract class CallIdSequence
extends Object

Responsible for generating callIds.

It is very important that for each next(Invocation), there is a matching complete(Invocation). If this doesn't match, than either the number of concurrent invocations can grow or shrink over time. This can lead to OOME or deadlock.

The CallIdSequence provides back pressure if enabled and there are too many concurrent invocations. When this happens, an exponential backoff policy is applied.

Currently a single CallIdSequence is used for all partitions; so there is contention. Also one partition can cause problems in other partition if a lot of invocations are created for that partition. Then other partitions can't make as many invocations because a single callIdSequence is being used.

In the future we could add a CallIdSequence per partition or using some 'concurrency level' and do a mod based on the partition-id. The advantage is that you reduce contention and improved isolation, at the expensive of:

1. increased complexity
2. not always being able to fully utilize the number of invocations.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	CallIdSequence.CallIdSequenceWithBackpressure A CallIdSequence that provided backpressure by taking the number in flight operations into account when a call-id needs to be determined.
static class	CallIdSequence.CallIdSequenceWithoutBackpressure

Constructor Summary

Constructors

Constructor and Description
CallIdSequence()

Method Summary

Methods

Modifier and Type	Method and Description
abstract void	complete(com.hazelcast.spi.impl.operationservice.impl.Invocation invocation)
abstract int	getMaxConcurrentInvocations() Returns the maximum concurrent invocations supported.
abstract long	next(com.hazelcast.spi.impl.operationservice.impl.Invocation invocation) Creates the next call-id.
protected boolean	skipRegistration(com.hazelcast.spi.impl.operationservice.impl.Invocation invocation) Not every call needs to be registered.

Methods inherited from class java.lang.Object

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

Constructor Detail

CallIdSequence

public CallIdSequence()

Method Detail

getMaxConcurrentInvocations

public abstract int getMaxConcurrentInvocations()

Returns the maximum concurrent invocations supported. Integer.MAX_VALUE means there is no max.

Returns:

the maximum concurrent invocation.

next

public abstract long next(com.hazelcast.spi.impl.operationservice.impl.Invocation invocation)

Creates the next call-id.

Operation.CALL_ID_LOCAL_SKIPPED is returned if local registration in the InvocationRegistry can be skipped.

Parameters:

invocation - the Invocation to create a call-id for.

Returns:

the generated callId.

Throws:

AssertionError - if invocation.op.callId not equals 0

complete

public abstract void complete(com.hazelcast.spi.impl.operationservice.impl.Invocation invocation)

skipRegistration

protected boolean skipRegistration(com.hazelcast.spi.impl.operationservice.impl.Invocation invocation)

Not every call needs to be registered. A call that is local and has no backups, doesn't need to be registered since there will not be a remote machine sending a response back to the invocation.

Parameters:

invocation -

Returns:

true if registration is required, false otherwise.