com.hazelcast.spi.impl.sequence

Interface CallIdSequence

All Known Implementing Classes:

AbstractCallIdSequence, CallIdSequenceWithBackpressure, CallIdSequenceWithoutBackpressure, FailFastCallIdSequence

public interface CallIdSequence

Responsible for generating invocation callIds.

It is very important that for each next() and forceNext() ()} there is a matching complete(). If they don't match, the number of concurrent invocations will grow/shrink without bound over time. This can lead to OOME or deadlock.

When backpressure is enabled and there are too many concurrent invocations, calls of next() will block using a spin-loop with exponential backoff.

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 improve isolation, at the expense of:

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

Method Summary

Modifier and Type	Method and Description
void	complete() Not idempotent: must be called exactly once per invocation.
long	concurrentInvocations() Returns the number of concurrent invocations.
long	forceNext() Generates the next unique call ID.
long	getLastCallId() Returns the last issued call ID.
int	getMaxConcurrentInvocations() Returns the maximum concurrent invocations supported.
long	next() Generates the next unique call ID.

Method Detail

getMaxConcurrentInvocations

int getMaxConcurrentInvocations()

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

Returns:

the maximum concurrent invocation.

next

long next()

Generates the next unique call ID. When the implementation supports backpressure, it will not return unless the number of outstanding invocations is within the configured limit. Instead it will block until the condition is met and eventually throw HazelcastOverloadException.

Returns:

the generated call ID

Throws:

HazelcastOverloadException - if the outstanding invocation count hasn't dropped below the configured limit

forceNext

long forceNext()

Generates the next unique call ID. This never blocks and it should be used only for urgent operation or when retrying.

Returns:

the generated call ID

complete

void complete()

Not idempotent: must be called exactly once per invocation.

getLastCallId

long getLastCallId()

Returns the last issued call ID. ONLY FOR TESTING. Must not be used for production code.

concurrentInvocations

long concurrentInvocations()

Returns the number of concurrent invocations.

Returns:

the number of concurrent invocations. Returns -1 if not known.