net.openhft.chronicle.core.threads

Interface EventLoop

All Superinterfaces:

AutoCloseable, Closeable, QueryCloseable

All Known Implementing Classes:

DelegatingEventLoop, OnDemandEventLoop

public interface EventLoop
extends Closeable

EventLoop represents an event-driven loop responsible for processing EventHandlers.

Implementations are not re-entrant. All state changes must occur on the event-loop thread to avoid race conditions. Typical usage is to add handlers before calling start() and then interact with the loop only from within its own thread.

The runsInsideCoreLoop() method allows callers to detect if the current thread is the core event thread. Code already running on the loop can call handlers directly rather than using an invokeAndWait-style mechanism.

Calling addHandler(EventHandler) after stop() results in an IllegalStateException.

Handler priorities control the relative frequency of handler invocation. The following table shows the approximate call frequency compared with HIGH priority:

 Priority            Relative frequency
 HIGH                1 (baseline)
 MEDIUM              ~1/4 of HIGH
 TIMER               ~1/16 of HIGH
 DAEMON              only when idle
 MONITOR             background thread
 BLOCKING            separate cached thread pool
 REPLICATION         alias of MEDIUM
 REPLICATION_TIMER   alias of TIMER
 CONCURRENT          alias of MEDIUM
 

Field Summary

Fields

Modifier and Type	Field and Description
static boolean	DEBUG_ADDING_HANDLERS
static boolean	DEBUG_REMOVING_HANDLERS

Method Summary

Modifier and Type	Method and Description
void	addHandler(EventHandler handler) Adds a handler to the event loop to be executed.
void	close() Stops the event loop and then closes any resources being held.
static boolean	inEventLoop() Checks if the current thread is executing inside an event loop.
boolean	isAlive() Checks if the main thread of the event loop is running.
boolean	isStopped() Checks if the event loop is in the stopped state.
String	name() Retrieves the name of the event loop.
default boolean	runsInsideCoreLoop() Checks if the current thread is the core thread of this event loop, or if this information cannot be determined.
void	start() Starts the event loop.
void	stop() Stops executing handlers and blocks until all handlers are complete.
void	unpause() Typically, implementations will unpause the event loop's pauser, if used.

Methods inherited from interface net.openhft.chronicle.core.io.Closeable

closeQuietly, closeQuietly

Methods inherited from interface net.openhft.chronicle.core.io.QueryCloseable

isClosed, isClosing

Field Detail

DEBUG_ADDING_HANDLERS

static final boolean DEBUG_ADDING_HANDLERS

DEBUG_REMOVING_HANDLERS

static final boolean DEBUG_REMOVING_HANDLERS

Method Detail

name

String name()

Retrieves the name of the event loop.

Returns:

the name of the event loop.

addHandler

void addHandler(EventHandler handler)

Adds a handler to the event loop to be executed. The event loop should execute handlers in order of their priority. Handlers with the same priority have no guarantee of execution order. Handlers will not be executed before start() has been called.

Parameters:

handler - The handler to be added to the event loop.

Throws:

IllegalStateException - if the event loop has been stopped or closed.

start

void start()

Starts the event loop. Once the event loop is started, it begins executing handlers.

unpause

void unpause()

Typically, implementations will unpause the event loop's pauser, if used. This can be helpful in cases where the event loop was temporarily paused for some reason.

stop

void stop()

Stops executing handlers and blocks until all handlers are complete. It is not expected that event loops can then be restarted.

isAlive

boolean isAlive()

Checks if the main thread of the event loop is running.

Returns:

true if the main thread is running, otherwise false.

isStopped

boolean isStopped()

Checks if the event loop is in the stopped state.

Returns:

true if the event loop is in the stopped state, otherwise false.

inEventLoop

static boolean inEventLoop()

Checks if the current thread is executing inside an event loop.

Returns:

true if the current thread is executing inside an event loop, otherwise false.

close

void close()

Stops the event loop and then closes any resources being held. Blocks until all the handlers are stopped and closed.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

See Also:

AbstractCloseable.performClose()

runsInsideCoreLoop

default boolean runsInsideCoreLoop()

Checks if the current thread is the core thread of this event loop, or if this information cannot be determined. If the current thread is not the core event thread but any other, this method returns false.

Returns:

true unless the current thread is not the core event thread.