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Server functionality for HBase
/*
* 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;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
import org.apache.hadoop.hbase.util.Pair;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hbase.thirdparty.com.google.common.base.Preconditions;
/**
* Class to hold dead servers list and utility querying dead server list.
* Servers are added when they expire or when we find them in filesystem on startup.
* When a server crash procedure is queued, it will populate the processing list and
* then remove the server from processing list when done. Servers are removed from
* dead server list when a new instance is started over the old on same hostname and
* port or when new Master comes online tidying up after all initialization. Processing
* list and deadserver list are not tied together (you don't have to be in deadservers
* list to be processing and vice versa).
*/
@InterfaceAudience.Private
public class DeadServer {
private static final Logger LOG = LoggerFactory.getLogger(DeadServer.class);
/**
* Set of known dead servers. On znode expiration, servers are added here.
* This is needed in case of a network partitioning where the server's lease
* expires, but the server is still running. After the network is healed,
* and it's server logs are recovered, it will be told to call server startup
* because by then, its regions have probably been reassigned.
*/
private final Map deadServers = new HashMap<>();
/**
* Set of dead servers currently being processed by a SCP.
* Added to this list at the start of SCP and removed after it is done
* processing the crash.
*/
private final Set processingServers = new HashSet<>();
/**
* @param serverName server name.
* @return true if this server is on the dead servers list false otherwise
*/
public synchronized boolean isDeadServer(final ServerName serverName) {
return deadServers.containsKey(serverName);
}
/**
* Checks if there are currently any dead servers being processed by the
* master. Returns true if at least one region server is currently being
* processed as dead.
*
* @return true if any RS are being processed as dead
*/
synchronized boolean areDeadServersInProgress() {
return !processingServers.isEmpty();
}
public synchronized Set copyServerNames() {
Set clone = new HashSet<>(deadServers.size());
clone.addAll(deadServers.keySet());
return clone;
}
/**
* Adds the server to the dead server list if it's not there already.
*/
synchronized void putIfAbsent(ServerName sn) {
this.deadServers.putIfAbsent(sn, EnvironmentEdgeManager.currentTime());
processing(sn);
}
/**
* Add sn< to set of processing deadservers.
* @see #finish(ServerName)
*/
public synchronized void processing(ServerName sn) {
if (processingServers.add(sn)) {
// Only log on add.
LOG.debug("Processing {}; numProcessing={}", sn, processingServers.size());
}
}
/**
* Complete processing for this dead server.
* @param sn ServerName for the dead server.
* @see #processing(ServerName)
*/
public synchronized void finish(ServerName sn) {
if (processingServers.remove(sn)) {
LOG.debug("Removed {} from processing; numProcessing={}", sn, processingServers.size());
}
}
public synchronized int size() {
return deadServers.size();
}
synchronized boolean isEmpty() {
return deadServers.isEmpty();
}
/**
* Handles restart of a server. The new server instance has a different start code.
* The new start code should be greater than the old one. We don't check that here.
* Removes the old server from deadserver list.
*
* @param newServerName Servername as either host:port or
* host,port,startcode.
* @return true if this server was dead before and coming back alive again
*/
synchronized boolean cleanPreviousInstance(final ServerName newServerName) {
Iterator it = deadServers.keySet().iterator();
while (it.hasNext()) {
if (cleanOldServerName(newServerName, it)) {
return true;
}
}
return false;
}
synchronized void cleanAllPreviousInstances(final ServerName newServerName) {
Iterator it = deadServers.keySet().iterator();
while (it.hasNext()) {
cleanOldServerName(newServerName, it);
}
}
/**
* @param newServerName Server to match port and hostname against.
* @param deadServerIterator Iterator primed so can call 'next' on it.
* @return True if newServerName and current primed
* iterator ServerName have same host and port and we removed old server
* from iterator and from processing list.
*/
private boolean cleanOldServerName(ServerName newServerName,
Iterator deadServerIterator) {
ServerName sn = deadServerIterator.next();
if (ServerName.isSameAddress(sn, newServerName)) {
// Remove from dead servers list. Don't remove from the processing list --
// let the SCP do it when it is done.
deadServerIterator.remove();
return true;
}
return false;
}
@Override
public synchronized String toString() {
// Display unified set of servers from both maps
Set servers = new HashSet<>();
servers.addAll(deadServers.keySet());
servers.addAll(processingServers);
StringBuilder sb = new StringBuilder();
for (ServerName sn : servers) {
if (sb.length() > 0) {
sb.append(", ");
}
sb.append(sn.toString());
// Star entries that are being processed
if (processingServers.contains(sn)) {
sb.append("*");
}
}
return sb.toString();
}
/**
* Extract all the servers dead since a given time, and sort them.
* @param ts the time, 0 for all
* @return a sorted array list, by death time, lowest values first.
*/
synchronized List> copyDeadServersSince(long ts) {
List> res = new ArrayList<>(size());
for (Map.Entry entry:deadServers.entrySet()){
if (entry.getValue() >= ts){
res.add(new Pair<>(entry.getKey(), entry.getValue()));
}
}
Collections.sort(res, (o1, o2) -> o1.getSecond().compareTo(o2.getSecond()));
return res;
}
/**
* Get the time when a server died
* @param deadServerName the dead server name
* @return the date when the server died
*/
public synchronized Date getTimeOfDeath(final ServerName deadServerName){
Long time = deadServers.get(deadServerName);
return time == null ? null : new Date(time);
}
/**
* Called from rpc by operator cleaning up deadserver list.
* @param deadServerName the dead server name
* @return true if this server was removed
*/
public synchronized boolean removeDeadServer(final ServerName deadServerName) {
Preconditions.checkState(!processingServers.contains(deadServerName),
"Asked to remove server still in processingServers set " + deadServerName +
" (numProcessing=" + processingServers.size() + ")");
return this.deadServers.remove(deadServerName) != null;
}
}