Package org.voltdb.client

Class Client2RequestGate

java.lang.Object

org.voltdb.client.Client2RequestGate

public class Client2RequestGate
extends Object

Provides a way to automatically handle Client2 request queue backpressure by blocking the calling thread.

Procedure calls are queued in the Client2 API for the duration of their execution. If the application is queueing calls faster than they can be processed, particularly when using callProcedureAsync, eventually the queue will reach its limit. The application can be made aware of an approaching limit by implementing a handler for "request backpressure" events; the application is expected to take whatever steps are needed in order to reduce the call rate. If it does not, then eventually the hard limit will be reached, and further calls will be rejected until the queue length falls below that limit.

Execution will not be blocked internally to the API when calling callProcedureAsync.

In some simple cases, it may nevertheless be appropriate to simply block execution of a thread that is about to issue callProcedureAsync This class, Client2RequestGate, facilitates that.

See Also:

• Client2
• Client2Config

Constructor Summary

Constructors

Constructor	Description
Client2RequestGate()

Method Summary

Modifier and Type	Method	Description
void	operate(boolean closing)	Set current state of the request gate.
void	waitOpen()	Await gate opening.
void	waitOpen(long timeout, TimeUnit unit)	Await gate opening with timeout.

Methods inherited from class java.lang.Object

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

Constructor Details

Client2RequestGate

public Client2RequestGate()

Method Details

waitOpen

public void waitOpen()
              throws InterruptedException

Await gate opening.

Usage: a call to this should be placed immediately before each callProcedureAsync request. It returns immediately, unless execution is blocked.

Throws:

InterruptedException

See Also:

• Client2.callProcedureAsync(java.lang.String, java.lang.Object...)

waitOpen

public void waitOpen(long timeout,
 TimeUnit unit)
              throws TimeoutException,
InterruptedException

Await gate opening with timeout.

Usage: a call to this should be placed immediately before each callProcedureAsync request. It returns immediately, unless execution is blocked.

Parameters:

timeout - the timeout interval

unit - the units in which the timeout was expressed

Throws:

TimeoutException

InterruptedException

See Also:

• Client2.callProcedureAsync(java.lang.String, java.lang.Object...)

operate

public void operate(boolean closing)

Set current state of the request gate.

Usage: configure this method as the request-backpressure handler in your application, before creating client instances. Here, gate is an instance of Client2RequestGate.

config.requestBackpressureHandler(gate::operate)

The notification is triggered when the queue length rises above the warning limit, and again when the queue length falls below the resume limit.

Parameters:

closing - true if gate is closing, false if opening

See Also:

• Client2Config.clientRequestLimit(int)
• Client2Config.clientRequestBackpressureLevel(int, int)
• Client2Config.requestBackpressureHandler(org.voltdb.client.Client2Notification.RequestBackpressure)