/**
*
* 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.master.handler;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.NavigableMap;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.HRegionInfo;
import org.apache.hadoop.hbase.Server;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.catalog.CatalogTracker;
import org.apache.hadoop.hbase.catalog.MetaEditor;
import org.apache.hadoop.hbase.catalog.MetaReader;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.executor.EventHandler;
import org.apache.hadoop.hbase.master.AssignmentManager;
import org.apache.hadoop.hbase.master.DeadServer;
import org.apache.hadoop.hbase.master.MasterServices;
import org.apache.hadoop.hbase.master.RegionState;
import org.apache.hadoop.hbase.master.RegionStates;
import org.apache.hadoop.hbase.master.ServerManager;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.PairOfSameType;
import org.apache.hadoop.hbase.zookeeper.ZKAssign;
import org.apache.zookeeper.KeeperException;
/**
* Process server shutdown.
* Server-to-handle must be already in the deadservers lists. See
* {@link ServerManager#expireServer(ServerName)}
*/
@InterfaceAudience.Private
public class ServerShutdownHandler extends EventHandler {
private static final Log LOG = LogFactory.getLog(ServerShutdownHandler.class);
private final ServerName serverName;
private final MasterServices services;
private final DeadServer deadServers;
private final boolean shouldSplitHlog; // whether to split HLog or not
public ServerShutdownHandler(final Server server, final MasterServices services,
final DeadServer deadServers, final ServerName serverName,
final boolean shouldSplitHlog) {
this(server, services, deadServers, serverName, EventType.M_SERVER_SHUTDOWN,
shouldSplitHlog);
}
ServerShutdownHandler(final Server server, final MasterServices services,
final DeadServer deadServers, final ServerName serverName, EventType type,
final boolean shouldSplitHlog) {
super(server, type);
this.serverName = serverName;
this.server = server;
this.services = services;
this.deadServers = deadServers;
if (!this.deadServers.contains(this.serverName)) {
LOG.warn(this.serverName + " is NOT in deadservers; it should be!");
}
this.shouldSplitHlog = shouldSplitHlog;
}
@Override
public String getInformativeName() {
if (serverName != null) {
return this.getClass().getSimpleName() + " for " + serverName;
} else {
return super.getInformativeName();
}
}
/**
* Before assign the ROOT region, ensure it haven't
* been assigned by other place
* <p>
* Under some scenarios, the ROOT region can be opened twice, so it seemed online
* in two regionserver at the same time.
* If the ROOT region has been assigned, so the operation can be canceled.
* @throws InterruptedException
* @throws IOException
* @throws KeeperException
*/
private void verifyAndAssignRoot()
throws InterruptedException, IOException, KeeperException {
long timeout = this.server.getConfiguration().
getLong("hbase.catalog.verification.timeout", 1000);
if (!this.server.getCatalogTracker().verifyRootRegionLocation(timeout)) {
this.services.getAssignmentManager().assignRoot();
}
}
/**
* Failed many times, shutdown processing
* @throws IOException
*/
private void verifyAndAssignRootWithRetries() throws IOException {
int iTimes = this.server.getConfiguration().getInt(
"hbase.catalog.verification.retries", 10);
long waitTime = this.server.getConfiguration().getLong(
"hbase.catalog.verification.timeout", 1000);
int iFlag = 0;
while (true) {
try {
verifyAndAssignRoot();
break;
} catch (KeeperException e) {
this.server.abort("In server shutdown processing, assigning root", e);
throw new IOException("Aborting", e);
} catch (Exception e) {
if (iFlag >= iTimes) {
this.server.abort("verifyAndAssignRoot failed after" + iTimes
+ " times retries, aborting", e);
throw new IOException("Aborting", e);
}
try {
Thread.sleep(waitTime);
} catch (InterruptedException e1) {
LOG.warn("Interrupted when is the thread sleep", e1);
Thread.currentThread().interrupt();
throw new IOException("Interrupted", e1);
}
iFlag++;
}
}
}
/**
* @return True if the server we are processing was carrying <code>-ROOT-</code>
*/
boolean isCarryingRoot() {
return false;
}
/**
* @return True if the server we are processing was carrying <code>.META.</code>
*/
boolean isCarryingMeta() {
return false;
}
@Override
public String toString() {
String name = "UnknownServerName";
if(server != null && server.getServerName() != null) {
name = server.getServerName().toString();
}
return getClass().getSimpleName() + "-" + name + "-" + getSeqid();
}
@Override
public void process() throws IOException {
final ServerName serverName = this.serverName;
try {
try {
if (this.shouldSplitHlog) {
LOG.info("Splitting logs for " + serverName);
this.services.getMasterFileSystem().splitLog(serverName);
} else {
LOG.info("Skipping log splitting for " + serverName);
}
} catch (IOException ioe) {
this.services.getExecutorService().submit(this);
this.deadServers.add(serverName);
throw new IOException("failed log splitting for " +
serverName + ", will retry", ioe);
}
// Assign root and meta if we were carrying them.
if (isCarryingRoot()) { // -ROOT-
LOG.info("Server " + serverName +
" was carrying ROOT. Trying to assign.");
this.services.getAssignmentManager().
regionOffline(HRegionInfo.ROOT_REGIONINFO);
verifyAndAssignRootWithRetries();
}
// Carrying meta?
if (isCarryingMeta()) {
LOG.info("Server " + serverName +
" was carrying META. Trying to assign.");
this.services.getAssignmentManager().
regionOffline(HRegionInfo.FIRST_META_REGIONINFO);
this.services.getAssignmentManager().assignMeta();
}
// We don't want worker thread in the MetaServerShutdownHandler
// executor pool to block by waiting availability of -ROOT-
// and .META. server. Otherwise, it could run into the following issue:
// 1. The current MetaServerShutdownHandler instance For RS1 waits for the .META.
// to come online.
// 2. The newly assigned .META. region server RS2 was shutdown right after
// it opens the .META. region. So the MetaServerShutdownHandler
// instance For RS1 will still be blocked.
// 3. The new instance of MetaServerShutdownHandler for RS2 is queued.
// 4. The newly assigned .META. region server RS3 was shutdown right after
// it opens the .META. region. So the MetaServerShutdownHandler
// instance For RS1 and RS2 will still be blocked.
// 5. The new instance of MetaServerShutdownHandler for RS3 is queued.
// 6. Repeat until we run out of MetaServerShutdownHandler worker threads
// The solution here is to resubmit a ServerShutdownHandler request to process
// user regions on that server so that MetaServerShutdownHandler
// executor pool is always available.
//
// If AssignmentManager hasn't finished rebuilding user regions,
// we are not ready to assign dead regions either. So we re-queue up
// the dead server for further processing too.
if (isCarryingRoot() || isCarryingMeta() // -ROOT- or .META.
|| !services.getAssignmentManager().isFailoverCleanupDone()) {
this.services.getServerManager().processDeadServer(serverName);
return;
}
// Wait on meta to come online; we need it to progress.
// TODO: Best way to hold strictly here? We should build this retry logic
// into the MetaReader operations themselves.
// TODO: Is the reading of .META. necessary when the Master has state of
// cluster in its head? It should be possible to do without reading .META.
// in all but one case. On split, the RS updates the .META.
// table and THEN informs the master of the split via zk nodes in
// 'unassigned' dir. Currently the RS puts ephemeral nodes into zk so if
// the regionserver dies, these nodes do not stick around and this server
// shutdown processing does fixup (see the fixupDaughters method below).
// If we wanted to skip the .META. scan, we'd have to change at least the
// final SPLIT message to be permanent in zk so in here we'd know a SPLIT
// completed (zk is updated after edits to .META. have gone in). See
// {@link SplitTransaction}. We'd also have to be figure another way for
// doing the below .META. daughters fixup.
NavigableMap<HRegionInfo, Result> hris = null;
while (!this.server.isStopped()) {
try {
this.server.getCatalogTracker().waitForMeta();
hris = MetaReader.getServerUserRegions(this.server.getCatalogTracker(),
this.serverName);
break;
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
throw new IOException("Interrupted", e);
} catch (IOException ioe) {
LOG.info("Received exception accessing META during server shutdown of " +
serverName + ", retrying META read", ioe);
}
}
if (this.server.isStopped()) {
throw new IOException("Server is stopped");
}
// Clean out anything in regions in transition. Being conservative and
// doing after log splitting. Could do some states before -- OPENING?
// OFFLINE? -- and then others after like CLOSING that depend on log
// splitting.
AssignmentManager am = services.getAssignmentManager();
List<RegionState> regionsInTransition = am.processServerShutdown(serverName);
LOG.info("Reassigning " + ((hris == null)? 0: hris.size()) +
" region(s) that " + (serverName == null? "null": serverName) +
" was carrying (skipping " + regionsInTransition.size() +
" regions(s) that are already in transition)");
// Iterate regions that were on this server and assign them
if (hris != null) {
RegionStates regionStates = am.getRegionStates();
List<HRegionInfo> toAssignRegions = new ArrayList<HRegionInfo>();
for (Map.Entry<HRegionInfo, Result> e: hris.entrySet()) {
HRegionInfo hri = e.getKey();
RegionState rit = regionStates.getRegionTransitionState(hri);
if (processDeadRegion(hri, e.getValue(), am, server.getCatalogTracker())) {
ServerName addressFromAM = regionStates.getRegionServerOfRegion(hri);
if (addressFromAM != null && !addressFromAM.equals(this.serverName)) {
// If this region is in transition on the dead server, it must be
// opening or pending_open, which is covered by AM#processServerShutdown
LOG.debug("Skip assigning region " + hri.getRegionNameAsString()
+ " because it has been opened in " + addressFromAM.getServerName());
continue;
}
if (rit != null) {
if (!rit.isOnServer(serverName)
|| rit.isClosed() || rit.isOpened() || rit.isSplit()) {
// Skip regions that are in transition on other server,
// or in state closed/opened/split
LOG.info("Skip assigning region " + rit);
continue;
}
try{
//clean zk node
LOG.info("Reassigning region with rs = " + rit + " and deleting zk node if exists");
ZKAssign.deleteNodeFailSilent(services.getZooKeeper(), hri);
} catch (KeeperException ke) {
this.server.abort("Unexpected ZK exception deleting unassigned node " + hri, ke);
return;
}
}
toAssignRegions.add(hri);
} else if (rit != null) {
if (rit.isSplitting() || rit.isSplit()) {
// This will happen when the RS went down and the call back for the SPLIITING or SPLIT
// has not yet happened for node Deleted event. In that case if the region was actually
// split
// but the RS had gone down before completing the split process then will not try to
// assign the parent region again. In that case we should make the region offline and
// also delete the region from RIT.
am.regionOffline(hri);
} else if ((rit.isClosing() || rit.isPendingClose())
&& am.getZKTable().isDisablingOrDisabledTable(hri.getTableNameAsString())) {
// If the table was partially disabled and the RS went down, we should clear the RIT
// and remove the node for the region.
// The rit that we use may be stale in case the table was in DISABLING state
// but though we did assign we will not be clearing the znode in CLOSING state.
// Doing this will have no harm. See HBASE-5927
am.deleteClosingOrClosedNode(hri);
am.regionOffline(hri);
} else {
LOG.warn("THIS SHOULD NOT HAPPEN: unexpected region in transition "
+ rit + " not to be assigned by SSH of server " + serverName);
}
}
}
try {
am.assign(toAssignRegions);
} catch (InterruptedException ie) {
LOG.error("Caught " + ie + " during round-robin assignment");
throw new IOException(ie);
}
}
} finally {
this.deadServers.finish(serverName);
}
LOG.info("Finished processing of shutdown of " + serverName);
}
/**
* Process a dead region from a dead RS. Checks if the region is disabled or
* disabling or if the region has a partially completed split.
* @param hri
* @param result
* @param assignmentManager
* @param catalogTracker
* @return Returns true if specified region should be assigned, false if not.
* @throws IOException
*/
public static boolean processDeadRegion(HRegionInfo hri, Result result,
AssignmentManager assignmentManager, CatalogTracker catalogTracker)
throws IOException {
boolean tablePresent = assignmentManager.getZKTable().isTablePresent(
hri.getTableNameAsString());
if (!tablePresent) {
LOG.info("The table " + hri.getTableNameAsString()
+ " was deleted. Hence not proceeding.");
return false;
}
// If table is not disabled but the region is offlined,
boolean disabled = assignmentManager.getZKTable().isDisabledTable(
hri.getTableNameAsString());
if (disabled){
LOG.info("The table " + hri.getTableNameAsString()
+ " was disabled. Hence not proceeding.");
return false;
}
if (hri.isOffline() && hri.isSplit()) {
LOG.debug("Offlined and split region " + hri.getRegionNameAsString() +
"; checking daughter presence");
if (MetaReader.getRegion(catalogTracker, hri.getRegionName()) == null) {
return false;
}
fixupDaughters(result, assignmentManager, catalogTracker);
return false;
}
boolean disabling = assignmentManager.getZKTable().isDisablingTable(
hri.getTableNameAsString());
if (disabling) {
LOG.info("The table " + hri.getTableNameAsString()
+ " is disabled. Hence not assigning region" + hri.getEncodedName());
return false;
}
return true;
}
/**
* Check that daughter regions are up in .META. and if not, add them.
* @param hris All regions for this server in meta.
* @param result The contents of the parent row in .META.
* @return the number of daughters missing and fixed
* @throws IOException
*/
public static int fixupDaughters(final Result result,
final AssignmentManager assignmentManager,
final CatalogTracker catalogTracker)
throws IOException {
PairOfSameType<HRegionInfo> daughters = HRegionInfo.getDaughterRegions(result);
int fixedA = fixupDaughter(result, daughters.getFirst(),
assignmentManager, catalogTracker);
int fixedB = fixupDaughter(result, daughters.getSecond(),
assignmentManager, catalogTracker);
return fixedA + fixedB;
}
/**
* Check individual daughter is up in .META.; fixup if its not.
* @param result The contents of the parent row in .META.
* @param qualifier Which daughter to check for.
* @return 1 if the daughter is missing and fixed. Otherwise 0
* @throws IOException
*/
static int fixupDaughter(final Result result, HRegionInfo daughter,
final AssignmentManager assignmentManager,
final CatalogTracker catalogTracker)
throws IOException {
if (daughter == null) return 0;
if (isDaughterMissing(catalogTracker, daughter)) {
LOG.info("Fixup; missing daughter " + daughter.getRegionNameAsString());
MetaEditor.addDaughter(catalogTracker, daughter, null);
// TODO: Log WARN if the regiondir does not exist in the fs. If its not
// there then something wonky about the split -- things will keep going
// but could be missing references to parent region.
// And assign it.
assignmentManager.assign(daughter, true, true);
return 1;
} else {
LOG.debug("Daughter " + daughter.getRegionNameAsString() + " present");
}
return 0;
}
/**
* Look for presence of the daughter OR of a split of the daughter in .META.
* Daughter could have been split over on regionserver before a run of the
* catalogJanitor had chance to clear reference from parent.
* @param daughter Daughter region to search for.
* @throws IOException
*/
private static boolean isDaughterMissing(final CatalogTracker catalogTracker,
final HRegionInfo daughter) throws IOException {
FindDaughterVisitor visitor = new FindDaughterVisitor(daughter);
// Start the scan at what should be the daughter's row in the .META.
// We will either 1., find the daughter or some derivative split of the
// daughter (will have same table name and start row at least but will sort
// after because has larger regionid -- the regionid is timestamp of region
// creation), OR, we will not find anything with same table name and start
// row. If the latter, then assume daughter missing and do fixup.
byte [] startrow = daughter.getRegionName();
MetaReader.fullScan(catalogTracker, visitor, startrow);
return !visitor.foundDaughter();
}
/**
* Looks for daughter. Sets a flag if daughter or some progeny of daughter
* is found up in <code>.META.</code>.
*/
static class FindDaughterVisitor implements MetaReader.Visitor {
private final HRegionInfo daughter;
private boolean found = false;
FindDaughterVisitor(final HRegionInfo daughter) {
this.daughter = daughter;
}
/**
* @return True if we found a daughter region during our visiting.
*/
boolean foundDaughter() {
return this.found;
}
@Override
public boolean visit(Result r) throws IOException {
HRegionInfo hri =
HRegionInfo.getHRegionInfo(r);
if (hri == null) {
LOG.warn("No serialized HRegionInfo in " + r);
return true;
}
byte [] value = r.getValue(HConstants.CATALOG_FAMILY,
HConstants.SERVER_QUALIFIER);
// See if daughter is assigned to some server
if (value == null) return false;
// Now see if we have gone beyond the daughter's startrow.
if (!Bytes.equals(daughter.getTableName(),
hri.getTableName())) {
// We fell into another table. Stop scanning.
return false;
}
// If our start rows do not compare, move on.
if (!Bytes.equals(daughter.getStartKey(), hri.getStartKey())) {
return false;
}
// Else, table name and start rows compare. It means that the daughter
// or some derivative split of the daughter is up in .META. Daughter
// exists.
this.found = true;
return false;
}
}
}