org.apache.zookeeper.server

Class NIOServerCnxnFactory.SelectorThread

java.lang.Object

java.lang.Thread

org.apache.zookeeper.server.ZooKeeperThread

org.apache.zookeeper.server.NIOServerCnxnFactory.SelectorThread

All Implemented Interfaces:

Runnable

Enclosing class:

NIOServerCnxnFactory

public class NIOServerCnxnFactory.SelectorThread
extends ZooKeeperThread

The SelectorThread receives newly accepted connections from the AcceptThread and is responsible for selecting for I/O readiness across the connections. This thread is the only thread that performs any non-threadsafe or potentially blocking calls on the selector (registering new connections and reading/writing interest ops). Assignment of a connection to a SelectorThread is permanent and only one SelectorThread will ever interact with the connection. There are 1-N SelectorThreads, with connections evenly apportioned between the SelectorThreads. If there is a worker thread pool, when a connection has I/O to perform the SelectorThread removes it from selection by clearing its interest ops and schedules the I/O for processing by a worker thread. When the work is complete, the connection is placed on the ready queue to have its interest ops restored and resume selection. If there is no worker thread pool, the SelectorThread performs the I/O directly.

Nested Class Summary

Nested classes/interfaces inherited from class java.lang.Thread

Thread.State, Thread.UncaughtExceptionHandler

Field Summary

Fields inherited from class java.lang.Thread

MAX_PRIORITY, MIN_PRIORITY, NORM_PRIORITY

Constructor Summary

Constructors

Constructor and Description
SelectorThread(int id)

Method Summary

Modifier and Type	Method and Description
boolean	addAcceptedConnection(SocketChannel accepted) Place new accepted connection onto a queue for adding.
boolean	addInterestOpsUpdateRequest(SelectionKey sk) Place interest op update requests onto a queue so that only the selector thread modifies interest ops, because interest ops reads/sets are potentially blocking operations if other select operations are happening.
void	run() The main loop for the thread selects() on the connections and dispatches ready I/O work requests, then registers all pending newly accepted connections and updates any interest ops on the queue.

Methods inherited from class org.apache.zookeeper.server.ZooKeeperThread

handleException

Methods inherited from class java.lang.Thread

activeCount, checkAccess, clone, countStackFrames, currentThread, destroy, dumpStack, enumerate, getAllStackTraces, getContextClassLoader, getDefaultUncaughtExceptionHandler, getId, getName, getPriority, getStackTrace, getState, getThreadGroup, getUncaughtExceptionHandler, holdsLock, interrupt, interrupted, isAlive, isDaemon, isInterrupted, join, join, join, resume, setContextClassLoader, setDaemon, setDefaultUncaughtExceptionHandler, setName, setPriority, setUncaughtExceptionHandler, sleep, sleep, start, stop, stop, suspend, toString, yield

Methods inherited from class java.lang.Object

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

Constructor Detail

SelectorThread

public SelectorThread(int id)
               throws IOException

Throws:

IOException

Method Detail

addAcceptedConnection

public boolean addAcceptedConnection(SocketChannel accepted)

Place new accepted connection onto a queue for adding. Do this so only the selector thread modifies what keys are registered with the selector.

addInterestOpsUpdateRequest

public boolean addInterestOpsUpdateRequest(SelectionKey sk)

Place interest op update requests onto a queue so that only the selector thread modifies interest ops, because interest ops reads/sets are potentially blocking operations if other select operations are happening.

run

public void run()

The main loop for the thread selects() on the connections and dispatches ready I/O work requests, then registers all pending newly accepted connections and updates any interest ops on the queue.

Specified by:

run in interface Runnable

Overrides:

run in class Thread