SshFenceByTcpPort.java
/**
* 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.ha;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.util.Collection;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.classification.VisibleForTesting;
import com.jcraft.jsch.ChannelExec;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.JSchException;
import com.jcraft.jsch.Session;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* This fencing implementation sshes to the target node and uses
* <code>fuser</code> to kill the process listening on the service's
* TCP port. This is more accurate than using "jps" since it doesn't
* require parsing, and will work even if there are multiple service
* processes running on the same machine.<p>
* It returns a successful status code if:
* <ul>
* <li><code>fuser</code> indicates it successfully killed a process, <em>or</em>
* <li><code>nc -z</code> indicates that nothing is listening on the target port
* </ul>
* <p>
* This fencing mechanism is configured as following in the fencing method
* list:
* <code>sshfence([[username][:ssh-port]])</code>
* where the optional argument specifies the username and port to use
* with ssh.
* <p>
* In order to achieve passwordless SSH, the operator must also configure
* <code>dfs.ha.fencing.ssh.private-key-files</code> to point to an
* SSH key that has passphrase-less access to the given username and host.
*/
public class SshFenceByTcpPort extends Configured
implements FenceMethod {
static final Logger LOG = LoggerFactory.getLogger(SshFenceByTcpPort.class);
static final String CONF_CONNECT_TIMEOUT_KEY =
"dfs.ha.fencing.ssh.connect-timeout";
private static final int CONF_CONNECT_TIMEOUT_DEFAULT =
30*1000;
static final String CONF_IDENTITIES_KEY =
"dfs.ha.fencing.ssh.private-key-files";
/**
* Verify that the argument, if given, in the conf is parseable.
*/
@Override
public void checkArgs(String argStr) throws BadFencingConfigurationException {
if (argStr != null) {
new Args(argStr);
}
}
@Override
public boolean tryFence(HAServiceTarget target, String argsStr)
throws BadFencingConfigurationException {
Args args = new Args(argsStr);
InetSocketAddress serviceAddr = target.getAddress();
String host = serviceAddr.getHostName();
Session session;
try {
session = createSession(serviceAddr.getHostName(), args);
} catch (JSchException e) {
LOG.warn("Unable to create SSH session", e);
return false;
}
LOG.info("Connecting to " + host + "...");
try {
session.connect(getSshConnectTimeout());
} catch (JSchException e) {
LOG.warn("Unable to connect to " + host
+ " as user " + args.user, e);
return false;
}
LOG.info("Connected to " + host);
try {
return doFence(session, serviceAddr);
} catch (JSchException e) {
LOG.warn("Unable to achieve fencing on remote host", e);
return false;
} finally {
session.disconnect();
}
}
private Session createSession(String host, Args args) throws JSchException {
JSch jsch = new JSch();
for (String keyFile : getKeyFiles()) {
jsch.addIdentity(keyFile);
}
JSch.setLogger(new LogAdapter());
Session session = jsch.getSession(args.user, host, args.sshPort);
session.setConfig("StrictHostKeyChecking", "no");
return session;
}
private boolean doFence(Session session, InetSocketAddress serviceAddr)
throws JSchException {
int port = serviceAddr.getPort();
try {
LOG.info("Looking for process running on port " + port);
int rc = execCommand(session,
"PATH=$PATH:/sbin:/usr/sbin fuser -v -k -n tcp " + port);
if (rc == 0) {
LOG.info("Successfully killed process that was " +
"listening on port " + port);
// exit code 0 indicates the process was successfully killed.
return true;
} else if (rc == 1) {
// exit code 1 indicates either that the process was not running
// or that fuser didn't have root privileges in order to find it
// (eg running as a different user)
LOG.info(
"Indeterminate response from trying to kill service. " +
"Verifying whether it is running using nc...");
rc = execCommand(session, "nc -z " + serviceAddr.getHostName() +
" " + serviceAddr.getPort());
if (rc == 0) {
// the service is still listening - we are unable to fence
LOG.warn("Unable to fence - it is running but we cannot kill it");
return false;
} else {
LOG.info("Verified that the service is down.");
return true;
}
} else {
// other
}
LOG.info("rc: " + rc);
return rc == 0;
} catch (InterruptedException e) {
LOG.warn("Interrupted while trying to fence via ssh", e);
return false;
} catch (IOException e) {
LOG.warn("Unknown failure while trying to fence via ssh", e);
return false;
}
}
/**
* Execute a command through the ssh session, pumping its
* stderr and stdout to our own logs.
*/
private int execCommand(Session session, String cmd)
throws JSchException, InterruptedException, IOException {
LOG.debug("Running cmd: " + cmd);
ChannelExec exec = null;
try {
exec = (ChannelExec)session.openChannel("exec");
exec.setCommand(cmd);
exec.setInputStream(null);
exec.connect();
// Pump stdout of the command to our WARN logs
StreamPumper outPumper = new StreamPumper(LOG, cmd + " via ssh",
exec.getInputStream(), StreamPumper.StreamType.STDOUT);
outPumper.start();
// Pump stderr of the command to our WARN logs
StreamPumper errPumper = new StreamPumper(LOG, cmd + " via ssh",
exec.getErrStream(), StreamPumper.StreamType.STDERR);
errPumper.start();
outPumper.join();
errPumper.join();
return exec.getExitStatus();
} finally {
cleanup(exec);
}
}
private static void cleanup(ChannelExec exec) {
if (exec != null) {
try {
exec.disconnect();
} catch (Throwable t) {
LOG.warn("Couldn't disconnect ssh channel", t);
}
}
}
private int getSshConnectTimeout() {
return getConf().getInt(
CONF_CONNECT_TIMEOUT_KEY, CONF_CONNECT_TIMEOUT_DEFAULT);
}
private Collection<String> getKeyFiles() {
return getConf().getTrimmedStringCollection(CONF_IDENTITIES_KEY);
}
/**
* Container for the parsed arg line for this fencing method.
*/
@VisibleForTesting
static class Args {
private static final Pattern USER_PORT_RE = Pattern.compile(
"([^:]+?)?(?:\\:(\\d+))?");
private static final int DEFAULT_SSH_PORT = 22;
String user;
int sshPort;
public Args(String arg)
throws BadFencingConfigurationException {
user = System.getProperty("user.name");
sshPort = DEFAULT_SSH_PORT;
// Parse optional user and ssh port
if (arg != null && !arg.isEmpty()) {
Matcher m = USER_PORT_RE.matcher(arg);
if (!m.matches()) {
throw new BadFencingConfigurationException(
"Unable to parse user and SSH port: "+ arg);
}
if (m.group(1) != null) {
user = m.group(1);
}
if (m.group(2) != null) {
sshPort = parseConfiggedPort(m.group(2));
}
}
}
private int parseConfiggedPort(String portStr)
throws BadFencingConfigurationException {
try {
return Integer.parseInt(portStr);
} catch (NumberFormatException nfe) {
throw new BadFencingConfigurationException(
"Port number '" + portStr + "' invalid");
}
}
}
/**
* Adapter from JSch's logger interface to our log4j
*/
private static class LogAdapter implements com.jcraft.jsch.Logger {
static final Logger LOG = LoggerFactory.getLogger(
SshFenceByTcpPort.class.getName() + ".jsch");
@Override
public boolean isEnabled(int level) {
switch (level) {
case com.jcraft.jsch.Logger.DEBUG:
return LOG.isDebugEnabled();
case com.jcraft.jsch.Logger.INFO:
return LOG.isInfoEnabled();
case com.jcraft.jsch.Logger.WARN:
return LOG.isWarnEnabled();
case com.jcraft.jsch.Logger.ERROR:
case com.jcraft.jsch.Logger.FATAL:
return LOG.isErrorEnabled();
default:
return false;
}
}
@Override
public void log(int level, String message) {
switch (level) {
case com.jcraft.jsch.Logger.DEBUG:
LOG.debug(message);
break;
case com.jcraft.jsch.Logger.INFO:
LOG.info(message);
break;
case com.jcraft.jsch.Logger.WARN:
LOG.warn(message);
break;
case com.jcraft.jsch.Logger.ERROR:
case com.jcraft.jsch.Logger.FATAL:
LOG.error(message);
break;
default:
break;
}
}
}
}