Package org.atmosphere.interceptor

Class BackpressureInterceptor

java.lang.Object

org.atmosphere.cpr.AtmosphereInterceptorAdapter

org.atmosphere.interceptor.BackpressureInterceptor

All Implemented Interfaces:

AtmosphereInterceptor, AtmosphereConfigAware, InvokationOrder

public class BackpressureInterceptor
extends AtmosphereInterceptorAdapter

Backpressure interceptor that tracks per-client pending message counts and applies a configurable policy (drop-oldest, drop-newest, or disconnect) when a client exceeds the high water mark.

Since:

4.0

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static enum	BackpressureInterceptor.Policy	Backpressure drop policy.

Nested classes/interfaces inherited from interface org.atmosphere.interceptor.InvokationOrder

InvokationOrder.PRIORITY

Field Summary

Fields inherited from interface org.atmosphere.interceptor.InvokationOrder

AFTER_DEFAULT, BEFORE_DEFAULT, FIRST_BEFORE_DEFAULT

Constructor Summary

Constructors

Constructor	Description
BackpressureInterceptor()

Method Summary

Modifier and Type	Method	Description
boolean	allowMessage(String uuid)	Check if a message can be delivered to the given resource.
void	configure(int highWaterMark, BackpressureInterceptor.Policy policy)	Programmatically configure the high water mark and drop policy.
void	configure(AtmosphereConfig config)	Configure an AtmosphereFramework object.
int	highWaterMark()
Action	inspect(AtmosphereResource r)	Invoked before an AtmosphereResource gets dispatched to AtmosphereHandler.
void	messageDelivered(String uuid)	Signal that a previously counted pending message has left the write queue (delivered to the client or evicted by a drop policy).
int	pendingCount(String uuid)
BackpressureInterceptor.Policy	policy()
static BackpressureInterceptor.Policy	policyFromString(String policyStr)	Parse a policy string (case-insensitive) into a BackpressureInterceptor.Policy.
String	toString()
long	totalDisconnects()
long	totalDrops()

Methods inherited from class org.atmosphere.cpr.AtmosphereInterceptorAdapter

destroy, postInspect, priority

Methods inherited from class java.lang.Object

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

Constructor Details

BackpressureInterceptor

public BackpressureInterceptor()

Method Details

configure

public void configure(AtmosphereConfig config)

Description copied from interface: AtmosphereConfigAware

Configure an AtmosphereFramework object.

Specified by:

configure in interface AtmosphereConfigAware

Overrides:

configure in class AtmosphereInterceptorAdapter

Parameters:

config - AtmosphereConfig

configure

public void configure(int highWaterMark,
 BackpressureInterceptor.Policy policy)

Programmatically configure the high water mark and drop policy. Used by consumers (such as the DefaultBroadcaster write path) that resolve the policy from their own configuration rather than from interceptor init parameters.

Parameters:

highWaterMark - the per-client pending high water mark (values < 1 are clamped to 1)

policy - the drop policy to apply once the high water mark is exceeded

policyFromString

public static BackpressureInterceptor.Policy policyFromString(String policyStr)

Parse a policy string (case-insensitive) into a BackpressureInterceptor.Policy. Unknown values fall back to BackpressureInterceptor.Policy.DROP_OLDEST.

Parameters:

policyStr - the policy string, e.g. drop-oldest, drop-newest, disconnect

Returns:

the resolved policy

inspect

public Action inspect(AtmosphereResource r)

Description copied from interface: AtmosphereInterceptor

Invoked before an AtmosphereResource gets dispatched to AtmosphereHandler.

Specified by:

inspect in interface AtmosphereInterceptor

Overrides:

inspect in class AtmosphereInterceptorAdapter

Parameters:

r - a AtmosphereResource

Returns:

Action.CONTINUE or Action.SUSPEND to dispatch the AtmosphereResource to other AtmosphereInterceptor or AtmosphereHandler. Return Action.TYPE.CANCELLED to stop the processing.

allowMessage

public boolean allowMessage(String uuid)

Check if a message can be delivered to the given resource. Call this before queueing a message for delivery.

Parameters:

uuid - the resource UUID

Returns:

true if the message should be delivered, false if dropped

messageDelivered

public void messageDelivered(String uuid)

Signal that a previously counted pending message has left the write queue (delivered to the client or evicted by a drop policy). Decrements the per-client pending count, never below zero. Consumers wiring allowMessage(String) into a real write/queue path MUST call this once per message removed from the queue, otherwise the pending count leaks upward and every message is eventually treated as over-limit.

Parameters:

uuid - the resource UUID

pendingCount

public int pendingCount(String uuid)

Returns:

the number of pending messages for the given resource

totalDrops

public long totalDrops()

Returns:

total messages dropped due to backpressure

totalDisconnects

public long totalDisconnects()

Returns:

total clients disconnected due to backpressure

highWaterMark

public int highWaterMark()

Returns:

the configured high water mark

policy

public BackpressureInterceptor.Policy policy()

Returns:

the configured policy

toString

public String toString()

Overrides:

toString in class AtmosphereInterceptorAdapter