Package pl.morgwai.base.servlet.utils

Class WebsocketPingerService

java.lang.Object

pl.morgwai.base.servlet.utils.WebsocketPingerService

public class WebsocketPingerService
extends Object

Automatically pings and handles pongs from websocket connections. Depending on constructor used, operates in either ping-pong mode or keep-alive-only mode.

Instances are usually created at app startup and stored in a location easily reachable for endpoint instances (for example on static var in app's ServletContextListener).

Endpoint instances should register themselves for pinging in their Endpoint.onOpen(Session, jakarta.websocket.EndpointConfig) method using addConnection(Session) and deregister in Endpoint.onClose(Session, CloseReason) using removeConnection(Session).

Field Summary

Fields

Modifier and Type	Field	Description
static int	DEFAULT_FAILURE_LIMIT	Arbitrarily chosen number.
static int	DEFAULT_INTERVAL	Majority of proxy and NAT routers have timeout of at least 60s.
static int	DEFAULT_PING_SIZE	Economic value to reduce use of Random.

Constructor Summary

Constructors

Constructor	Description
WebsocketPingerService()	Calls WebsocketPingerService(DEFAULT_INTERVAL, DEFAULT_FAILURE_LIMIT, DEFAULT_PING_SIZE, false) (ping-pong mode).
WebsocketPingerService(int intervalSeconds)	Calls WebsocketPingerService(intervalSeconds, false) (keep-alive-only mode).
WebsocketPingerService(int intervalSeconds, boolean synchronizeSending)	Configures and starts the service in keep-alive-only mode: just 1 byte is sent each time and responses are not expected.
WebsocketPingerService(int intervalSeconds, int failureLimit, int pingSize)	Calls WebsocketPingerService(intervalSeconds, failureLimit, pingSize, false) (ping-pong mode).
WebsocketPingerService(int intervalSeconds, int failureLimit, int pingSize, boolean synchronizeSending)	Configures and starts the service in ping-pong mode.

Method Summary

Modifier and Type	Method	Description
void	addConnection(Session connection)	Registers connection for pinging.
int	getNumberOfConnections()	Returns the number of currently registered connections.
void	removeConnection(Session connection)	Deregisters connection.
Set<Session>	stop()	Stops the service.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_INTERVAL

public static final int DEFAULT_INTERVAL

Majority of proxy and NAT routers have timeout of at least 60s.

See Also:

Constant Field Values

DEFAULT_FAILURE_LIMIT

public static final int DEFAULT_FAILURE_LIMIT

Arbitrarily chosen number.

See Also:

Constant Field Values

DEFAULT_PING_SIZE

public static final int DEFAULT_PING_SIZE

Economic value to reduce use of Random.

See Also:

Constant Field Values

Constructor Detail

WebsocketPingerService

public WebsocketPingerService(int intervalSeconds,
                              int failureLimit,
                              int pingSize,
                              boolean synchronizeSending)

Configures and starts the service in ping-pong mode.

Parameters:

intervalSeconds - interval between pings.

failureLimit - limit of lost or malformed pongs after which the given connection is closed. Pongs received after pingIntervalSeconds count as failures. Each valid, timely pong resets connection's failure counter.

pingSize - size of the ping data to send. This comes from Random, so an economic value is recommended.

synchronizeSending - whether to synchronize ping sending on the given connection. Whether it is necessary depends on the implementation of the container. For example it is not necessary on Jetty, but it is on Tomcat: see this bug report.

WebsocketPingerService

public WebsocketPingerService(int intervalSeconds,
                              int failureLimit,
                              int pingSize)

Calls WebsocketPingerService(intervalSeconds, failureLimit, pingSize, false) (ping-pong mode).

WebsocketPingerService

public WebsocketPingerService()

Calls WebsocketPingerService(DEFAULT_INTERVAL, DEFAULT_FAILURE_LIMIT, DEFAULT_PING_SIZE, false) (ping-pong mode).

WebsocketPingerService

public WebsocketPingerService(int intervalSeconds,
                              boolean synchronizeSending)

Configures and starts the service in keep-alive-only mode: just 1 byte is sent each time and responses are not expected. Remaining params have the same meaning as in WebsocketPingerService(int, int, int, boolean).

WebsocketPingerService

public WebsocketPingerService(int intervalSeconds)

Calls WebsocketPingerService(intervalSeconds, false) (keep-alive-only mode).

Method Detail

addConnection

public void addConnection(Session connection)

Registers connection for pinging. Usually called in Endpoint.onOpen(Session, jakarta.websocket.EndpointConfig).

removeConnection

public void removeConnection(Session connection)

Deregisters connection. Usually called in Endpoint.onClose(Session, CloseReason).

getNumberOfConnections

public int getNumberOfConnections()

Returns the number of currently registered connections.

stop

public Set<Session> stop()

Stops the service. After a call to this method the service becomes no longer usable and should be discarded.

Returns:

remaining registered connections.