Class StatusChecker

java.lang.Object

org.simpleframework.http.socket.service.StatusChecker

All Implemented Interfaces:

Runnable

class StatusChecker
extends Object
implements Runnable

The StatusChecker object is used to perform health checks on connected sessions. Health is determined using the ping pong protocol defined in RFC 6455. The ping pong protocol requires that any endpoint must respond to a ping control frame with a pong control frame containing the same payload. This session checker will send out out ping controls frames and wait for a pong frame. If it does not receive a pong frame after a configured expiry time then it will close the associated session.

Field Summary

Fields

Modifier and Type	Field	Description
private final Channel	channel	This is the underling TCP channel that is being checked.
private final FrameConnection	connection	This is the WebSocket this this pinger will be monitoring.
private final AtomicLong	counter	This is a count of the number of unacknowledged ping frames.
private final Reason	error	The only reason for a close is for an unexpected error.
private final Frame	frame	This is the frame that contains the ping to send.
private final long	frequency	This is the frequency with which the checker should run.
private final StatusResultListener	listener	This is used to perform the monitoring of the sessions.
private final Reason	normal	The only reason for a close is for an unexpected error.
private final Scheduler	scheduler	This is the shared scheduler used to execute this checker.
private final Trace	trace	This is used to trace various events for this pinger.

Constructor Summary

Constructors

Constructor	Description
StatusChecker(FrameConnection connection, Request request, Scheduler scheduler, long frequency)	Constructor for the StatusChecker object.

Method Summary

Modifier and Type	Method	Description
void	close()	This is used to close the session and send a 1000 close code to the client indicating a normal closure.
void	failure()	This is used to close the session and send a 1011 close code to the client indicating an internal server error.
void	refresh()	If the connection gets a response to its ping message then this will reset the internal counter.
void	run()	This method is used to check to see if a session has expired.
void	start()	This is used to kick of the status checking.

Methods inherited from class Object

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

Field Details

listener

private final StatusResultListener listener

This is used to perform the monitoring of the sessions.

connection

private final FrameConnection connection

This is the WebSocket this this pinger will be monitoring.

scheduler

private final Scheduler scheduler

This is the shared scheduler used to execute this checker.

counter

private final AtomicLong counter

This is a count of the number of unacknowledged ping frames.

channel

private final Channel channel

This is the underling TCP channel that is being checked.

normal

private final Reason normal

The only reason for a close is for an unexpected error.

error

private final Reason error

The only reason for a close is for an unexpected error.

trace

private final Trace trace

This is used to trace various events for this pinger.

frame

private final Frame frame

This is the frame that contains the ping to send.

frequency

private final long frequency

This is the frequency with which the checker should run.

Constructor Details

StatusChecker

public StatusChecker(FrameConnection connection,
 Request request,
 Scheduler scheduler,
 long frequency)

Constructor for the StatusChecker object. This is used to create a pinger that will send out ping frames at a specified interval. If a session does not respond within three times the duration of the ping the connection is reset.

Parameters:

connection - this is the WebSocket to send the frames

request - this is the associated request

scheduler - this is the scheduler used to execute this

frequency - this is the frequency with which to ping

Method Details

start

public void start()

This is used to kick of the status checking. Here an initial ping is sent over the socket and the task is then scheduled to check the result after the frequency period has expired. If this method fails for any reason the TCP channel is closed.

run

public void run()

This method is used to check to see if a session has expired. If there have been three unacknowledged ping events then this will force a closure of the WebSocket connection. This is done to ensure only healthy connections are maintained within the server, also RFC 6455 recommends using the ping pong protocol.

Specified by:

run in interface Runnable

refresh

public void refresh()

If the connection gets a response to its ping message then this will reset the internal counter. This ensure that the connection does not time out. If after three pings there is not response from the other side then the connection will be terminated.

failure

public void failure()

This is used to close the session and send a 1011 close code to the client indicating an internal server error. Closing of the session in this manner only occurs if there is an expiry of the session or an I/O error, both of which are unexpected and violate the behaviour as defined in RFC 6455.

close

public void close()

This is used to close the session and send a 1000 close code to the client indicating a normal closure. This will be called when there is a close notification dispatched to the status listener. Typically here a graceful closure is best.