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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 org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
import org.apache.hadoop.hbase.util.Pair;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
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;
/**
* Class to hold dead servers list and utility querying dead server list.
* On znode expiration, servers are added here.
*/
@InterfaceAudience.Private
public class DeadServer {
private static final Log LOG = LogFactory.getLog(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();
/**
* Number of dead servers currently being processed
*/
private int numProcessing = 0;
/**
* Whether a dead server is being processed currently.
*/
private boolean processing = false;
/**
* A dead server that comes back alive has a different start code. The new start code should be
* greater than the old one, but we don't take this into account in this method.
*
* @param newServerName Servername as either host:port or
* host,port,startcode.
* @return true if this server was dead before and coming back alive again
*/
public synchronized boolean cleanPreviousInstance(final ServerName newServerName) {
Iterator it = deadServers.keySet().iterator();
while (it.hasNext()) {
ServerName sn = it.next();
if (ServerName.isSameHostnameAndPort(sn, newServerName)) {
it.remove();
return true;
}
}
return false;
}
/**
* @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
*/
public synchronized boolean areDeadServersInProgress() { return processing; }
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.
* @param sn the server name
*/
public synchronized void add(ServerName sn) {
processing = true;
if (!deadServers.containsKey(sn)){
deadServers.put(sn, EnvironmentEdgeManager.currentTime());
}
}
/**
* Notify that we started processing this dead server.
* @param sn ServerName for the dead server.
*/
public synchronized void notifyServer(ServerName sn) {
if (LOG.isDebugEnabled()) { LOG.debug("Started processing " + sn); }
processing = true;
numProcessing++;
}
public synchronized void finish(ServerName sn) {
numProcessing--;
if (LOG.isDebugEnabled()) LOG.debug("Finished " + sn + "; numProcessing=" + numProcessing);
assert numProcessing >= 0: "Number of dead servers in processing should always be non-negative";
if (numProcessing < 0) {
LOG.error("Number of dead servers in processing = " + numProcessing
+ ". Something went wrong, this should always be non-negative.");
numProcessing = 0;
}
if (numProcessing == 0) { processing = false; }
}
public synchronized int size() {
return deadServers.size();
}
public synchronized boolean isEmpty() {
return deadServers.isEmpty();
}
public synchronized void cleanAllPreviousInstances(final ServerName newServerName) {
Iterator it = deadServers.keySet().iterator();
while (it.hasNext()) {
ServerName sn = it.next();
if (ServerName.isSameHostnameAndPort(sn, newServerName)) {
it.remove();
}
}
}
public synchronized String toString() {
StringBuilder sb = new StringBuilder();
for (ServerName sn : deadServers.keySet()) {
if (sb.length() > 0) {
sb.append(", ");
}
sb.append(sn.toString());
}
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.
*/
public 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, ServerNameDeathDateComparator);
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);
}
private static Comparator> ServerNameDeathDateComparator =
new Comparator>(){
@Override
public int compare(Pair o1, Pair o2) {
return o1.getSecond().compareTo(o2.getSecond());
}
};
}