/**
* 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.master;
import java.io.IOException;
import java.net.InetAddress;
import java.util.ArrayList;
import java.util.Collections;
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 java.util.concurrent.ConcurrentHashMap;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.ClockOutOfSyncException;
import org.apache.hadoop.hbase.HRegionInfo;
import org.apache.hadoop.hbase.HServerAddress;
import org.apache.hadoop.hbase.HServerLoad;
import org.apache.hadoop.hbase.PleaseHoldException;
import org.apache.hadoop.hbase.Server;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.YouAreDeadException;
import org.apache.hadoop.hbase.ZooKeeperConnectionException;
import org.apache.hadoop.hbase.client.HConnection;
import org.apache.hadoop.hbase.client.HConnectionManager;
import org.apache.hadoop.hbase.client.RetriesExhaustedException;
import org.apache.hadoop.hbase.ipc.HRegionInterface;
import org.apache.hadoop.hbase.master.handler.MetaServerShutdownHandler;
import org.apache.hadoop.hbase.master.handler.ServerShutdownHandler;
import org.apache.hadoop.hbase.monitoring.MonitoredTask;
import org.apache.hadoop.hbase.regionserver.RegionOpeningState;
/**
* The ServerManager class manages info about region servers.
* <p>
* Maintains lists of online and dead servers. Processes the startups,
* shutdowns, and deaths of region servers.
* <p>
* Servers are distinguished in two different ways. A given server has a
* location, specified by hostname and port, and of which there can only be one
* online at any given time. A server instance is specified by the location
* (hostname and port) as well as the startcode (timestamp from when the server
* was started). This is used to differentiate a restarted instance of a given
* server from the original instance.
*/
public class ServerManager {
public static final String WAIT_ON_REGIONSERVERS_MAXTOSTART =
"hbase.master.wait.on.regionservers.maxtostart";
public static final String WAIT_ON_REGIONSERVERS_MINTOSTART =
"hbase.master.wait.on.regionservers.mintostart";
public static final String WAIT_ON_REGIONSERVERS_TIMEOUT =
"hbase.master.wait.on.regionservers.timeout";
public static final String WAIT_ON_REGIONSERVERS_INTERVAL =
"hbase.master.wait.on.regionservers.interval";
private static final Log LOG = LogFactory.getLog(ServerManager.class);
// Set if we are to shutdown the cluster.
private volatile boolean clusterShutdown = false;
/** Map of registered servers to their current load */
private final Map<ServerName, HServerLoad> onlineServers =
new ConcurrentHashMap<ServerName, HServerLoad>();
// TODO: This is strange to have two maps but HSI above is used on both sides
/**
* Map from full server-instance name to the RPC connection for this server.
*/
private final Map<ServerName, HRegionInterface> serverConnections =
new HashMap<ServerName, HRegionInterface>();
/**
* List of region servers <ServerName> that should not get any more new
* regions.
*/
private final ArrayList<ServerName> drainingServers =
new ArrayList<ServerName>();
private final Server master;
private final MasterServices services;
private final HConnection connection;
private final DeadServer deadservers;
private final long maxSkew;
private final long warningSkew;
/**
* Set of region servers which are dead but not expired immediately. If one
* server died before master enables ServerShutdownHandler, the server will be
* added to set and will be expired through calling
* {@link ServerManager#expireDeadNotExpiredServers()} by master.
*/
private Set<ServerName> deadNotExpiredServers = new HashSet<ServerName>();
/**
* Flag to enable SSH for ROOT region server. It's used in master initialization to enable SSH for
* ROOT before META assignment.
*/
private boolean isSSHForRootEnabled = false;
/**
* Constructor.
* @param master
* @param services
* @throws ZooKeeperConnectionException
*/
public ServerManager(final Server master, final MasterServices services)
throws ZooKeeperConnectionException {
this(master, services, true);
}
ServerManager(final Server master, final MasterServices services,
final boolean connect) throws ZooKeeperConnectionException {
this.master = master;
this.services = services;
Configuration c = master.getConfiguration();
maxSkew = c.getLong("hbase.master.maxclockskew", 30000);
warningSkew = c.getLong("hbase.master.warningclockskew", 10000);
this.deadservers = new DeadServer();
this.connection = connect ? HConnectionManager.getConnection(c) : null;
}
/**
* Let the server manager know a new regionserver has come online
* @param ia The remote address
* @param port The remote port
* @param serverStartcode
* @param serverCurrentTime The current time of the region server in ms
* @return The ServerName we know this server as.
* @throws IOException
*/
ServerName regionServerStartup(final InetAddress ia, final int port,
final long serverStartcode, long serverCurrentTime)
throws IOException {
// Test for case where we get a region startup message from a regionserver
// that has been quickly restarted but whose znode expiration handler has
// not yet run, or from a server whose fail we are currently processing.
// Test its host+port combo is present in serverAddresstoServerInfo. If it
// is, reject the server and trigger its expiration. The next time it comes
// in, it should have been removed from serverAddressToServerInfo and queued
// for processing by ProcessServerShutdown.
ServerName sn = new ServerName(ia.getHostName(), port, serverStartcode);
checkClockSkew(sn, serverCurrentTime);
checkIsDead(sn, "STARTUP");
checkAlreadySameHostPort(sn);
recordNewServer(sn, HServerLoad.EMPTY_HSERVERLOAD);
return sn;
}
void regionServerReport(ServerName sn, HServerLoad hsl)
throws YouAreDeadException, PleaseHoldException {
checkIsDead(sn, "REPORT");
if (!this.onlineServers.containsKey(sn)) {
// Already have this host+port combo and its just different start code?
checkAlreadySameHostPort(sn);
// Just let the server in. Presume master joining a running cluster.
// recordNewServer is what happens at the end of reportServerStartup.
// The only thing we are skipping is passing back to the regionserver
// the ServerName to use. Here we presume a master has already done
// that so we'll press on with whatever it gave us for ServerName.
recordNewServer(sn, hsl);
} else {
this.onlineServers.put(sn, hsl);
}
}
/**
* Test to see if we have a server of same host and port already.
* @param serverName
* @throws PleaseHoldException
*/
void checkAlreadySameHostPort(final ServerName serverName)
throws PleaseHoldException {
ServerName existingServer =
ServerName.findServerWithSameHostnamePort(getOnlineServersList(), serverName);
if (existingServer != null) {
String message = "Server serverName=" + serverName +
" rejected; we already have " + existingServer.toString() +
" registered with same hostname and port";
LOG.info(message);
if (existingServer.getStartcode() < serverName.getStartcode()) {
LOG.info("Triggering server recovery; existingServer " +
existingServer + " looks stale, new server:" + serverName);
expireServer(existingServer);
}
if (services.isServerShutdownHandlerEnabled()) {
// master has completed the initialization
throw new PleaseHoldException(message);
}
}
}
/**
* Checks if the clock skew between the server and the master. If the clock skew exceeds the
* configured max, it will throw an exception; if it exceeds the configured warning threshold,
* it will log a warning but start normally.
* @param serverName Incoming servers's name
* @param serverCurrentTime
* @throws ClockOutOfSyncException if the skew exceeds the configured max value
*/
private void checkClockSkew(final ServerName serverName, final long serverCurrentTime)
throws ClockOutOfSyncException {
long skew = System.currentTimeMillis() - serverCurrentTime;
if (skew > maxSkew) {
String message = "Server " + serverName + " has been " +
"rejected; Reported time is too far out of sync with master. " +
"Time difference of " + skew + "ms > max allowed of " + maxSkew + "ms";
LOG.warn(message);
throw new ClockOutOfSyncException(message);
} else if (skew > warningSkew){
String message = "Reported time for server " + serverName + " is out of sync with master " +
"by " + skew + "ms. (Warning threshold is " + warningSkew + "ms; " +
"error threshold is " + maxSkew + "ms)";
LOG.warn(message);
}
}
/**
* If this server is on the dead list, reject it with a YouAreDeadException.
* If it was dead but came back with a new start code, remove the old entry
* from the dead list.
* @param serverName
* @param what START or REPORT
* @throws YouAreDeadException
*/
private void checkIsDead(final ServerName serverName, final String what)
throws YouAreDeadException {
if (this.deadservers.isDeadServer(serverName)) {
// host name, port and start code all match with existing one of the
// dead servers. So, this server must be dead.
String message = "Server " + what + " rejected; currently processing " +
serverName + " as dead server";
LOG.debug(message);
throw new YouAreDeadException(message);
}
// remove dead server with same hostname and port of newly checking in rs after master
// initialization.See HBASE-5916 for more information.
if ((this.services == null || ((HMaster) this.services).isInitialized())
&& this.deadservers.cleanPreviousInstance(serverName)) {
// This server has now become alive after we marked it as dead.
// We removed it's previous entry from the dead list to reflect it.
LOG.debug(what + ":" + " Server " + serverName + " came back up," +
" removed it from the dead servers list");
}
}
/**
* Adds the onlineServers list.
* @param hsl
* @param serverName The remote servers name.
*/
void recordNewServer(final ServerName serverName, final HServerLoad hsl) {
LOG.info("Registering server=" + serverName);
this.onlineServers.put(serverName, hsl);
this.serverConnections.remove(serverName);
}
/**
* @param serverName
* @return HServerLoad if serverName is known else null
*/
public HServerLoad getLoad(final ServerName serverName) {
return this.onlineServers.get(serverName);
}
/**
* @param address
* @return HServerLoad if serverName is known else null
* @deprecated Use {@link #getLoad(HServerAddress)}
*/
public HServerLoad getLoad(final HServerAddress address) {
ServerName sn = new ServerName(address.toString(), ServerName.NON_STARTCODE);
ServerName actual =
ServerName.findServerWithSameHostnamePort(this.getOnlineServersList(), sn);
return actual == null? null: getLoad(actual);
}
/**
* Compute the average load across all region servers.
* Currently, this uses a very naive computation - just uses the number of
* regions being served, ignoring stats about number of requests.
* @return the average load
*/
public double getAverageLoad() {
int totalLoad = 0;
int numServers = 0;
double averageLoad = 0.0;
for (HServerLoad hsl: this.onlineServers.values()) {
numServers++;
totalLoad += hsl.getNumberOfRegions();
}
averageLoad = (double)totalLoad / (double)numServers;
return averageLoad;
}
/** @return the count of active regionservers */
int countOfRegionServers() {
// Presumes onlineServers is a concurrent map
return this.onlineServers.size();
}
/**
* @return Read-only map of servers to serverinfo
*/
public Map<ServerName, HServerLoad> getOnlineServers() {
// Presumption is that iterating the returned Map is OK.
synchronized (this.onlineServers) {
return Collections.unmodifiableMap(this.onlineServers);
}
}
public Set<ServerName> getDeadServers() {
return this.deadservers.clone();
}
/**
* Checks if any dead servers are currently in progress.
* @return true if any RS are being processed as dead, false if not
*/
public boolean areDeadServersInProgress() {
return this.deadservers.areDeadServersInProgress();
}
void letRegionServersShutdown() {
long previousLogTime = 0;
while (!onlineServers.isEmpty()) {
if (System.currentTimeMillis() > (previousLogTime + 1000)) {
StringBuilder sb = new StringBuilder();
for (ServerName key : this.onlineServers.keySet()) {
if (sb.length() > 0) {
sb.append(", ");
}
sb.append(key);
}
LOG.info("Waiting on regionserver(s) to go down " + sb.toString());
previousLogTime = System.currentTimeMillis();
}
synchronized (onlineServers) {
try {
onlineServers.wait(100);
} catch (InterruptedException ignored) {
// continue
}
}
}
}
/*
* Expire the passed server. Add it to list of deadservers and queue a
* shutdown processing.
*/
public synchronized void expireServer(final ServerName serverName) {
boolean carryingRoot = services.getAssignmentManager().isCarryingRoot(serverName);
if (!services.isServerShutdownHandlerEnabled() && (!carryingRoot || !this.isSSHForRootEnabled)) {
LOG.info("Master doesn't enable ServerShutdownHandler during initialization, "
+ "delay expiring server " + serverName);
this.deadNotExpiredServers.add(serverName);
return;
}
if (!this.onlineServers.containsKey(serverName)) {
LOG.warn("Received expiration of " + serverName +
" but server is not currently online");
}
if (this.deadservers.contains(serverName)) {
// TODO: Can this happen? It shouldn't be online in this case?
LOG.warn("Received expiration of " + serverName +
" but server shutdown is already in progress");
return;
}
// Remove the server from the known servers lists and update load info BUT
// add to deadservers first; do this so it'll show in dead servers list if
// not in online servers list.
this.deadservers.add(serverName);
this.onlineServers.remove(serverName);
synchronized (onlineServers) {
onlineServers.notifyAll();
}
this.serverConnections.remove(serverName);
// If cluster is going down, yes, servers are going to be expiring; don't
// process as a dead server
if (this.clusterShutdown) {
LOG.info("Cluster shutdown set; " + serverName +
" expired; onlineServers=" + this.onlineServers.size());
if (this.onlineServers.isEmpty()) {
master.stop("Cluster shutdown set; onlineServer=0");
}
return;
}
boolean carryingMeta = services.getAssignmentManager().isCarryingMeta(serverName);
if (carryingRoot || carryingMeta) {
this.services.getExecutorService().submit(new MetaServerShutdownHandler(this.master,
this.services, this.deadservers, serverName, carryingRoot, carryingMeta));
} else {
this.services.getExecutorService().submit(new ServerShutdownHandler(this.master,
this.services, this.deadservers, serverName, true));
}
LOG.debug("Added=" + serverName +
" to dead servers, submitted shutdown handler to be executed, root=" +
carryingRoot + ", meta=" + carryingMeta);
}
/**
* Expire the servers which died during master's initialization. It will be
* called after HMaster#assignRootAndMeta.
* @throws IOException
* */
synchronized void expireDeadNotExpiredServers() throws IOException {
if (!services.isServerShutdownHandlerEnabled()) {
throw new IOException("Master hasn't enabled ServerShutdownHandler ");
}
Iterator<ServerName> serverIterator = deadNotExpiredServers.iterator();
while (serverIterator.hasNext()) {
expireServer(serverIterator.next());
serverIterator.remove();
}
}
/**
* Enable SSH for ROOT region server and expire ROOT which died during master's initialization. It
* will be called before Meta assignment.
* @throws IOException
*/
void enableSSHForRoot() throws IOException {
if (this.isSSHForRootEnabled) {
return;
}
this.isSSHForRootEnabled = true;
Iterator<ServerName> serverIterator = deadNotExpiredServers.iterator();
while (serverIterator.hasNext()) {
ServerName curServerName = serverIterator.next();
if (services.getAssignmentManager().isCarryingRoot(curServerName)) {
expireServer(curServerName);
serverIterator.remove();
}
}
}
/**
* Reset flag isSSHForRootEnabled to false
*/
void disableSSHForRoot() {
this.isSSHForRootEnabled = false;
}
/*
* Remove the server from the drain list.
*/
public boolean removeServerFromDrainList(final ServerName sn) {
// Warn if the server (sn) is not online. ServerName is of the form:
// <hostname> , <port> , <startcode>
if (!this.isServerOnline(sn)) {
LOG.warn("Server " + sn + " is not currently online. " +
"Removing from draining list anyway, as requested.");
}
// Remove the server from the draining servers lists.
return this.drainingServers.remove(sn);
}
/*
* Add the server to the drain list.
*/
public boolean addServerToDrainList(final ServerName sn) {
// Warn if the server (sn) is not online. ServerName is of the form:
// <hostname> , <port> , <startcode>
if (!this.isServerOnline(sn)) {
LOG.warn("Server " + sn + " is not currently online. " +
"Ignoring request to add it to draining list.");
return false;
}
// Add the server to the draining servers lists, if it's not already in
// it.
if (this.drainingServers.contains(sn)) {
LOG.warn("Server " + sn + " is already in the draining server list." +
"Ignoring request to add it again.");
return false;
}
return this.drainingServers.add(sn);
}
// RPC methods to region servers
/**
* Sends an OPEN RPC to the specified server to open the specified region.
* <p>
* Open should not fail but can if server just crashed.
* <p>
* @param server server to open a region
* @param region region to open
* @param versionOfOfflineNode that needs to be present in the offline node
* when RS tries to change the state from OFFLINE to other states.
*/
public RegionOpeningState sendRegionOpen(final ServerName server,
HRegionInfo region, int versionOfOfflineNode)
throws IOException {
HRegionInterface hri = getServerConnection(server);
if (hri == null) {
LOG.warn("Attempting to send OPEN RPC to server " + server.toString() +
" failed because no RPC connection found to this server");
return RegionOpeningState.FAILED_OPENING;
}
return (versionOfOfflineNode == -1) ? hri.openRegion(region) : hri
.openRegion(region, versionOfOfflineNode);
}
/**
* Sends an OPEN RPC to the specified server to open the specified region.
* <p>
* Open should not fail but can if server just crashed.
* <p>
* @param server server to open a region
* @param regions regions to open
*/
public void sendRegionOpen(ServerName server, List<HRegionInfo> regions)
throws IOException {
HRegionInterface hri = getServerConnection(server);
if (hri == null) {
LOG.warn("Attempting to send OPEN RPC to server " + server.toString() +
" failed because no RPC connection found to this server");
return;
}
hri.openRegions(regions);
}
/**
* Sends an CLOSE RPC to the specified server to close the specified region.
* <p>
* A region server could reject the close request because it either does not
* have the specified region or the region is being split.
* @param server server to open a region
* @param region region to open
* @param versionOfClosingNode
* the version of znode to compare when RS transitions the znode from
* CLOSING state.
* @return true if server acknowledged close, false if not
* @throws IOException
*/
public boolean sendRegionClose(ServerName server, HRegionInfo region,
int versionOfClosingNode) throws IOException {
if (server == null) throw new NullPointerException("Passed server is null");
HRegionInterface hri = getServerConnection(server);
if (hri == null) {
throw new IOException("Attempting to send CLOSE RPC to server " +
server.toString() + " for region " +
region.getRegionNameAsString() +
" failed because no RPC connection found to this server");
}
return hri.closeRegion(region, versionOfClosingNode);
}
/**
* @param sn
* @return
* @throws IOException
* @throws RetriesExhaustedException wrapping a ConnectException if failed
* putting up proxy.
*/
private HRegionInterface getServerConnection(final ServerName sn)
throws IOException {
HRegionInterface hri = this.serverConnections.get(sn);
if (hri == null) {
LOG.debug("New connection to " + sn.toString());
hri = this.connection.getHRegionConnection(sn.getHostname(), sn.getPort());
this.serverConnections.put(sn, hri);
}
return hri;
}
/**
* Wait for the region servers to report in.
* We will wait until one of this condition is met:
* - the master is stopped
* - the 'hbase.master.wait.on.regionservers.maxtostart' number of
* region servers is reached
* - the 'hbase.master.wait.on.regionservers.mintostart' is reached AND
* there have been no new region server in for
* 'hbase.master.wait.on.regionservers.interval' time AND
* the 'hbase.master.wait.on.regionservers.timeout' is reached
*
* @throws InterruptedException
*/
public void waitForRegionServers(MonitoredTask status)
throws InterruptedException {
final long interval = this.master.getConfiguration().
getLong(WAIT_ON_REGIONSERVERS_INTERVAL, 1500);
final long timeout = this.master.getConfiguration().
getLong(WAIT_ON_REGIONSERVERS_TIMEOUT, 4500);
int minToStart = this.master.getConfiguration().
getInt(WAIT_ON_REGIONSERVERS_MINTOSTART, 1);
if (minToStart < 1) {
LOG.warn(String.format(
"The value of '%s' (%d) can not be less than 1, ignoring.",
WAIT_ON_REGIONSERVERS_MINTOSTART, minToStart));
minToStart = 1;
}
int maxToStart = this.master.getConfiguration().
getInt(WAIT_ON_REGIONSERVERS_MAXTOSTART, Integer.MAX_VALUE);
if (maxToStart < minToStart) {
LOG.warn(String.format(
"The value of '%s' (%d) is set less than '%s' (%d), ignoring.",
WAIT_ON_REGIONSERVERS_MAXTOSTART, maxToStart,
WAIT_ON_REGIONSERVERS_MINTOSTART, minToStart));
maxToStart = Integer.MAX_VALUE;
}
long now = System.currentTimeMillis();
final long startTime = now;
long slept = 0;
long lastLogTime = 0;
long lastCountChange = startTime;
int count = countOfRegionServers();
int oldCount = 0;
while (
!this.master.isStopped() &&
count < maxToStart &&
(lastCountChange+interval > now || timeout > slept || count < minToStart)
){
// Log some info at every interval time or if there is a change
if (oldCount != count || lastLogTime+interval < now){
lastLogTime = now;
String msg =
"Waiting for region servers count to settle; currently"+
" checked in " + count + ", slept for " + slept + " ms," +
" expecting minimum of " + minToStart + ", maximum of "+ maxToStart+
", timeout of "+timeout+" ms, interval of "+interval+" ms.";
LOG.info(msg);
status.setStatus(msg);
}
// We sleep for some time
final long sleepTime = 50;
Thread.sleep(sleepTime);
now = System.currentTimeMillis();
slept = now - startTime;
oldCount = count;
count = countOfRegionServers();
if (count != oldCount) {
lastCountChange = now;
}
}
LOG.info("Finished waiting for region servers count to settle;" +
" checked in " + count + ", slept for " + slept + " ms," +
" expecting minimum of " + minToStart + ", maximum of "+ maxToStart+","+
" master is "+ (this.master.isStopped() ? "stopped.": "running.")
);
}
/**
* @return A copy of the internal list of online servers.
*/
public List<ServerName> getOnlineServersList() {
// TODO: optimize the load balancer call so we don't need to make a new list
// TODO: FIX. THIS IS POPULAR CALL.
return new ArrayList<ServerName>(this.onlineServers.keySet());
}
/**
* @return A copy of the internal list of draining servers.
*/
public List<ServerName> getDrainingServersList() {
return new ArrayList<ServerName>(this.drainingServers);
}
/**
* @return A copy of the internal set of deadNotExpired servers.
*/
Set<ServerName> getDeadNotExpiredServers() {
return new HashSet<ServerName>(this.deadNotExpiredServers);
}
public boolean isServerOnline(ServerName serverName) {
return onlineServers.containsKey(serverName);
}
public void shutdownCluster() {
this.clusterShutdown = true;
this.master.stop("Cluster shutdown requested");
}
public boolean isClusterShutdown() {
return this.clusterShutdown;
}
/**
* Stop the ServerManager. Currently closes the connection to the master.
*/
public void stop() {
if (connection != null) {
try {
connection.close();
} catch (IOException e) {
LOG.error("Attempt to close connection to master failed", e);
}
}
}
/**
* To clear any dead server with same host name and port of any online server
*/
void clearDeadServersWithSameHostNameAndPortOfOnlineServer() {
ServerName sn = null;
for (ServerName serverName : getOnlineServersList()) {
while ((sn = ServerName.
findServerWithSameHostnamePort(this.deadservers, serverName)) != null) {
this.deadservers.remove(sn);
}
}
}
}