org.janusgraph.diskstorage.util.backpressure

Class SemaphoreProtectedReleaseQueryBackPressure

java.lang.Object

org.janusgraph.diskstorage.util.backpressure.SemaphoreProtectedReleaseQueryBackPressure

All Implemented Interfaces:

QueryBackPressure

public class SemaphoreProtectedReleaseQueryBackPressure
extends Object
implements QueryBackPressure

Query back pressure implementation which uses Semaphore to control back pressure and has protection in place to not generate more `permits` than `backPressureLimit`.
This implementation is similar to SemaphoreQueryBackPressure with the exception that `releaseAfterQuery` calls are asynchronous (non-blocking) and protected against generating more `permits` than `backPressureLimit`. This comes with additional overhead of using a separate thread to process any new `release` calls which means that all calls to `releaseAfterQuery` will be processed in sequential order one by one. The first time logic registers that an attempt to add a new permit could potentially result in a bigger amount of `permits` than `backPressureLimit`, it logs a warning. Subsequent calls to `releaseAfterQuery` will not log such warning anymore.

Constructor Summary

Constructors

Constructor and Description
SemaphoreProtectedReleaseQueryBackPressure(int backPressureLimit)

Method Summary

Modifier and Type	Method and Description
void	acquireBeforeQuery() Acquires one slot.
void	close() Releases any resources related to the back pressure mechanism.
void	releaseAfterQuery() Releases one slot in non-blocking fashion.

Methods inherited from class java.lang.Object

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

Constructor Detail

SemaphoreProtectedReleaseQueryBackPressure

public SemaphoreProtectedReleaseQueryBackPressure(int backPressureLimit)

Method Detail

acquireBeforeQuery

public void acquireBeforeQuery()

Description copied from interface: QueryBackPressure

Acquires one slot. If not slots are available then this method will be blocked until a slot is available.

Specified by:

acquireBeforeQuery in interface QueryBackPressure

releaseAfterQuery

public void releaseAfterQuery()

Description copied from interface: QueryBackPressure

Releases one slot in non-blocking fashion. The successful execution of this method doesn't mean that the release is happened. Instead, execution of this method guarantees that the release will happen.

Specified by:

releaseAfterQuery in interface QueryBackPressure

close

public void close()

Description copied from interface: QueryBackPressure

Releases any resources related to the back pressure mechanism. Makes this instance unusable after that.

Specified by:

close in interface QueryBackPressure