Java tutorial
/** * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.hadoop.hbase.procedure; import java.io.Closeable; import java.io.IOException; import java.util.Collection; import java.util.concurrent.ConcurrentMap; import java.util.concurrent.ExecutorService; import java.util.concurrent.Future; import java.util.concurrent.RejectedExecutionException; import java.util.concurrent.SynchronousQueue; import java.util.concurrent.ThreadPoolExecutor; import java.util.concurrent.TimeUnit; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.hadoop.classification.InterfaceAudience; import org.apache.hadoop.hbase.DaemonThreadFactory; import org.apache.hadoop.hbase.errorhandling.ForeignException; import com.google.common.collect.MapMaker; /** * Process to kick off and manage a running {@link Subprocedure} on a member. This is the * specialized part of a {@link Procedure} that actually does procedure type-specific work * and reports back to the coordinator as it completes each phase. * <p> * If there is a connection error ({@link #controllerConnectionFailure(String, IOException)}), all * currently running subprocedures are notify to failed since there is no longer a way to reach any * other members or coordinators since the rpcs are down. */ @InterfaceAudience.Private public class ProcedureMember implements Closeable { private static final Log LOG = LogFactory.getLog(ProcedureMember.class); final static long KEEP_ALIVE_MILLIS_DEFAULT = 5000; private final SubprocedureFactory builder; private final ProcedureMemberRpcs rpcs; private final ConcurrentMap<String, Subprocedure> subprocs = new MapMaker().concurrencyLevel(4).weakValues() .makeMap(); private final ExecutorService pool; /** * Instantiate a new ProcedureMember. This is a slave that executes subprocedures. * * @param rpcs controller used to send notifications to the procedure coordinator * @param pool thread pool to submit subprocedures * @param factory class that creates instances of a subprocedure. */ public ProcedureMember(ProcedureMemberRpcs rpcs, ThreadPoolExecutor pool, SubprocedureFactory factory) { this.pool = pool; this.rpcs = rpcs; this.builder = factory; } /** * Default thread pool for the procedure * * @param memberName * @param procThreads the maximum number of threads to allow in the pool */ public static ThreadPoolExecutor defaultPool(String memberName, int procThreads) { return defaultPool(memberName, procThreads, KEEP_ALIVE_MILLIS_DEFAULT); } /** * Default thread pool for the procedure * * @param memberName * @param procThreads the maximum number of threads to allow in the pool * @param keepAliveMillis the maximum time (ms) that excess idle threads will wait for new tasks */ public static ThreadPoolExecutor defaultPool(String memberName, int procThreads, long keepAliveMillis) { return new ThreadPoolExecutor(1, procThreads, keepAliveMillis, TimeUnit.MILLISECONDS, new SynchronousQueue<Runnable>(), new DaemonThreadFactory("member: '" + memberName + "' subprocedure-pool")); } /** * Package exposed. Not for public use. * * @return reference to the Procedure member's rpcs object */ ProcedureMemberRpcs getRpcs() { return rpcs; } /** * This is separated from execution so that we can detect and handle the case where the * subprocedure is invalid and inactionable due to bad info (like DISABLED snapshot type being * sent here) * @param opName * @param data * @return subprocedure */ public Subprocedure createSubprocedure(String opName, byte[] data) { return builder.buildSubprocedure(opName, data); } /** * Submit an subprocedure for execution. This starts the local acquire phase. * @param subproc the subprocedure to execute. * @return <tt>true</tt> if the subprocedure was started correctly, <tt>false</tt> if it * could not be started. In the latter case, the subprocedure holds a reference to * the exception that caused the failure. */ public boolean submitSubprocedure(Subprocedure subproc) { // if the submitted subprocedure was null, bail. if (subproc == null) { LOG.warn("Submitted null subprocedure, nothing to run here."); return false; } String procName = subproc.getName(); if (procName == null || procName.length() == 0) { LOG.error("Subproc name cannot be null or the empty string"); return false; } // make sure we aren't already running an subprocedure of that name Subprocedure rsub; synchronized (subprocs) { rsub = subprocs.get(procName); } if (rsub != null) { if (!rsub.isComplete()) { LOG.error("Subproc '" + procName + "' is already running. Bailing out"); return false; } LOG.warn("A completed old subproc " + procName + " is still present, removing"); subprocs.remove(procName); } LOG.debug("Submitting new Subprocedure:" + procName); // kick off the subprocedure Future<Void> future = null; try { synchronized (subprocs) { subprocs.put(procName, subproc); } future = this.pool.submit(subproc); return true; } catch (RejectedExecutionException e) { synchronized (subprocs) { subprocs.remove(procName); } // the thread pool is full and we can't run the subprocedure String msg = "Subprocedure pool is full!"; subproc.cancel(msg, e.getCause()); // cancel all subprocedures proactively if (future != null) { future.cancel(true); } } LOG.error("Failed to start subprocedure '" + procName + "'"); return false; } /** * Notification that procedure coordinator has reached the global barrier * @param procName name of the subprocedure that should start running the the in-barrier phase */ public void receivedReachedGlobalBarrier(String procName) { Subprocedure subproc = subprocs.get(procName); if (subproc == null) { LOG.warn("Unexpected reached glabal barrier message for Sub-Procedure '" + procName + "'"); return; } subproc.receiveReachedGlobalBarrier(); } /** * Best effort attempt to close the threadpool via Thread.interrupt. */ @Override public void close() throws IOException { // have to use shutdown now to break any latch waiting pool.shutdownNow(); } /** * Shutdown the threadpool, and wait for upto timeoutMs millis before bailing * @param timeoutMs timeout limit in millis * @return true if successfully, false if bailed due to timeout. * @throws InterruptedException */ boolean closeAndWait(long timeoutMs) throws InterruptedException { pool.shutdown(); return pool.awaitTermination(timeoutMs, TimeUnit.MILLISECONDS); } /** * The connection to the rest of the procedure group (member and coordinator) has been * broken/lost/failed. This should fail any interested subprocedure, but not attempt to notify * other members since we cannot reach them anymore. * @param message description of the error * @param cause the actual cause of the failure * * TODO i'm tempted to just remove this code completely and treat it like any other abort. * Implementation wise, if this happens it is a ZK failure which means the RS will abort. */ public void controllerConnectionFailure(final String message, final IOException cause) { Collection<Subprocedure> toNotify = subprocs.values(); LOG.error(message, cause); for (Subprocedure sub : toNotify) { // TODO notify the elements, if they aren't null sub.cancel(message, cause); } } /** * Send abort to the specified procedure * @param procName name of the procedure to about * @param ee exception information about the abort */ public void receiveAbortProcedure(String procName, ForeignException ee) { LOG.debug("Request received to abort procedure " + procName, ee); // if we know about the procedure, notify it Subprocedure sub = subprocs.get(procName); if (sub == null) { LOG.info("Received abort on procedure with no local subprocedure " + procName + ", ignoring it.", ee); return; // Procedure has already completed } String msg = "Propagating foreign exception to subprocedure " + sub.getName(); LOG.error(msg, ee); sub.cancel(msg, ee); } }