/**
* Copyright 2010 The Apache Software Foundation
*
* 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.regionserver.handler;
import java.io.IOException;
import java.util.concurrent.atomic.AtomicBoolean;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.HRegionInfo;
import org.apache.hadoop.hbase.Server;
import org.apache.hadoop.hbase.executor.EventHandler;
import org.apache.hadoop.hbase.regionserver.HRegion;
import org.apache.hadoop.hbase.regionserver.RegionServerServices;
import org.apache.hadoop.hbase.util.CancelableProgressable;
import org.apache.hadoop.hbase.zookeeper.ZKAssign;
import org.apache.zookeeper.KeeperException;
/**
* Handles opening of a region on a region server.
* <p>
* This is executed after receiving an OPEN RPC from the master or client.
*/
public class OpenRegionHandler extends EventHandler {
private static final Log LOG = LogFactory.getLog(OpenRegionHandler.class);
private final RegionServerServices rsServices;
private final HRegionInfo regionInfo;
// We get version of our znode at start of open process and monitor it across
// the total open. We'll fail the open if someone hijacks our znode; we can
// tell this has happened if version is not as expected.
private volatile int version = -1;
public OpenRegionHandler(final Server server,
final RegionServerServices rsServices, HRegionInfo regionInfo) {
this(server, rsServices, regionInfo, EventType.M_RS_OPEN_REGION);
}
protected OpenRegionHandler(final Server server,
final RegionServerServices rsServices, final HRegionInfo regionInfo,
EventType eventType) {
super(server, eventType);
this.rsServices = rsServices;
this.regionInfo = regionInfo;
}
public HRegionInfo getRegionInfo() {
return regionInfo;
}
@Override
public void process() throws IOException {
final String name = regionInfo.getRegionNameAsString();
LOG.debug("Processing open of " + name);
if (this.server.isStopped() || this.rsServices.isStopping()) {
LOG.info("Server stopping or stopped, skipping open of " + name);
return;
}
final String encodedName = regionInfo.getEncodedName();
// Check that this region is not already online
HRegion region = this.rsServices.getFromOnlineRegions(encodedName);
if (region != null) {
LOG.warn("Attempted open of " + name +
" but already online on this server");
return;
}
// If fails, just return. Someone stole the region from under us.
// Calling transitionZookeeperOfflineToOpening initalizes this.version.
if (!transitionZookeeperOfflineToOpening(encodedName)) return;
// Open region. After a successful open, failures in subsequent processing
// needs to do a close as part of cleanup.
region = openRegion();
if (region == null) return;
boolean failed = true;
if (tickleOpening("post_region_open")) {
if (updateMeta(region)) failed = false;
}
if (failed || this.server.isStopped() || this.rsServices.isStopping()) {
cleanupFailedOpen(region);
return;
}
if (!transitionToOpened(region)) {
cleanupFailedOpen(region);
return;
}
// Done! Successful region open
LOG.debug("Opened " + name);
}
/**
* Update ZK, ROOT or META. This can take a while if for example the
* .META. is not available -- if server hosting .META. crashed and we are
* waiting on it to come back -- so run in a thread and keep updating znode
* state meantime so master doesn't timeout our region-in-transition.
* Caller must cleanup region if this fails.
*/
private boolean updateMeta(final HRegion r) {
if (this.server.isStopped() || this.rsServices.isStopping()) {
return false;
}
// Object we do wait/notify on. Make it boolean. If set, we're done.
// Else, wait.
final AtomicBoolean signaller = new AtomicBoolean(false);
PostOpenDeployTasksThread t = new PostOpenDeployTasksThread(r,
this.server, this.rsServices, signaller);
t.start();
int assignmentTimeout = this.server.getConfiguration().
getInt("hbase.master.assignment.timeoutmonitor.period", 10000);
// Total timeout for meta edit. If we fail adding the edit then close out
// the region and let it be assigned elsewhere.
long timeout = assignmentTimeout * 10;
long now = System.currentTimeMillis();
long endTime = now + timeout;
// Let our period at which we update OPENING state to be be 1/3rd of the
// regions-in-transition timeout period.
long period = Math.max(1, assignmentTimeout/ 3);
long lastUpdate = now;
while (!signaller.get() && t.isAlive() && !this.server.isStopped() &&
!this.rsServices.isStopping() && (endTime > now)) {
long elapsed = now - lastUpdate;
if (elapsed > period) {
// Only tickle OPENING if postOpenDeployTasks is taking some time.
lastUpdate = now;
tickleOpening("post_open_deploy");
}
synchronized (signaller) {
try {
signaller.wait(period);
} catch (InterruptedException e) {
// Go to the loop check.
}
}
now = System.currentTimeMillis();
}
// Is thread still alive? We may have left above loop because server is
// stopping or we timed out the edit. Is so, interrupt it.
if (t.isAlive()) {
if (!signaller.get()) {
// Thread still running; interrupt
LOG.debug("Interrupting thread " + t);
t.interrupt();
}
try {
t.join();
} catch (InterruptedException ie) {
LOG.warn("Interrupted joining " +
r.getRegionInfo().getRegionNameAsString(), ie);
Thread.currentThread().interrupt();
}
}
// Was there an exception opening the region? This should trigger on
// InterruptedException too. If so, we failed.
return !t.interrupted() && t.getException() == null;
}
/**
* Thread to run region post open tasks. Call {@link #getException()} after
* the thread finishes to check for exceptions running
* {@link RegionServerServices#postOpenDeployTasks(HRegion, org.apache.hadoop.hbase.catalog.CatalogTracker, boolean)}.
*/
static class PostOpenDeployTasksThread extends Thread {
private Exception exception = null;
private final Server server;
private final RegionServerServices services;
private final HRegion region;
private final AtomicBoolean signaller;
PostOpenDeployTasksThread(final HRegion region, final Server server,
final RegionServerServices services, final AtomicBoolean signaller) {
super("PostOpenDeployTasks:" + region.getRegionInfo().getEncodedName());
this.setDaemon(true);
this.server = server;
this.services = services;
this.region = region;
this.signaller = signaller;
}
public void run() {
try {
this.services.postOpenDeployTasks(this.region,
this.server.getCatalogTracker(), false);
} catch (Exception e) {
LOG.warn("Exception running postOpenDeployTasks; region=" +
this.region.getRegionInfo().getEncodedName(), e);
this.exception = e;
}
// We're done. Set flag then wake up anyone waiting on thread to complete.
this.signaller.set(true);
synchronized (this.signaller) {
this.signaller.notify();
}
}
/**
* @return Null or the run exception; call this method after thread is done.
*/
Exception getException() {
return this.exception;
}
}
/**
* @param r Region we're working on.
* @return Transition znode to OPENED state.
* @throws IOException
*/
private boolean transitionToOpened(final HRegion r) throws IOException {
boolean result = false;
HRegionInfo hri = r.getRegionInfo();
final String name = hri.getRegionNameAsString();
// Finally, Transition ZK node to OPENED
try {
if (ZKAssign.transitionNodeOpened(this.server.getZooKeeper(), hri,
this.server.getServerName(), this.version) == -1) {
LOG.warn("Completed the OPEN of region " + name +
" but when transitioning from " +
" OPENING to OPENED got a version mismatch, someone else clashed " +
"so now unassigning -- closing region");
} else {
result = true;
}
} catch (KeeperException e) {
LOG.error("Failed transitioning node " + name +
" from OPENING to OPENED -- closing region", e);
}
return result;
}
/**
* @return Instance of HRegion if successful open else null.
*/
private HRegion openRegion() {
HRegion region = null;
try {
// Instantiate the region. This also periodically tickles our zk OPENING
// state so master doesn't timeout this region in transition.
region = HRegion.openHRegion(this.regionInfo, this.rsServices.getWAL(),
this.server.getConfiguration(), this.rsServices.getFlushRequester(),
new CancelableProgressable() {
public boolean progress() {
// We may lose the znode ownership during the open. Currently its
// too hard interrupting ongoing region open. Just let it complete
// and check we still have the znode after region open.
return tickleOpening("open_region_progress");
}
});
} catch (IOException e) {
// We failed open. Let our znode expire in regions-in-transition and
// Master will assign elsewhere. Presumes nothing to close.
LOG.error("Failed open of region=" +
this.regionInfo.getRegionNameAsString(), e);
}
return region;
}
private void cleanupFailedOpen(final HRegion region) throws IOException {
if (region != null) region.close();
this.rsServices.removeFromOnlineRegions(regionInfo.getEncodedName());
}
/**
* Transition ZK node from OFFLINE to OPENING.
* @param encodedName Name of the znode file (Region encodedName is the znode
* name).
* @return True if successful transition.
*/
boolean transitionZookeeperOfflineToOpening(final String encodedName) {
// TODO: should also handle transition from CLOSED?
try {
// Initialize the znode version.
this.version =
ZKAssign.transitionNodeOpening(server.getZooKeeper(),
regionInfo, server.getServerName());
} catch (KeeperException e) {
LOG.error("Error transition from OFFLINE to OPENING for region=" +
encodedName, e);
}
boolean b = isGoodVersion();
if (!b) {
LOG.warn("Failed transition from OFFLINE to OPENING for region=" +
encodedName);
}
return b;
}
/**
* Update our OPENING state in zookeeper.
* Do this so master doesn't timeout this region-in-transition.
* @param context Some context to add to logs if failure
* @return True if successful transition.
*/
boolean tickleOpening(final String context) {
// If previous checks failed... do not try again.
if (!isGoodVersion()) return false;
String encodedName = this.regionInfo.getEncodedName();
try {
this.version =
ZKAssign.retransitionNodeOpening(server.getZooKeeper(),
this.regionInfo, this.server.getServerName(), this.version);
} catch (KeeperException e) {
server.abort("Exception refreshing OPENING; region=" + encodedName +
", context=" + context, e);
this.version = -1;
}
boolean b = isGoodVersion();
if (!b) {
LOG.warn("Failed refreshing OPENING; region=" + encodedName +
", context=" + context);
}
return b;
}
private boolean isGoodVersion() {
return this.version != -1;
}
}