org.apache.hadoop.ha
Class SshFenceByTcpPort

java.lang.Object
  org.apache.hadoop.conf.Configured
      org.apache.hadoop.ha.SshFenceByTcpPort

All Implemented Interfaces:

Configurable, FenceMethod

public class SshFenceByTcpPort
extends Configured
implements FenceMethod

This fencing implementation sshes to the target node and uses fuser 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.

It returns a successful status code if:

• fuser indicates it successfully killed a process, or
• nc -z indicates that nothing is listening on the target port

This fencing mechanism is configured as following in the fencing method list: sshfence([[username][:ssh-port]]) where the optional argument specifies the username and port to use with ssh.

In order to achieve passwordless SSH, the operator must also configure dfs.ha.fencing.ssh.private-key-files to point to an SSH key that has passphrase-less access to the given username and host.

Constructor Summary

SshFenceByTcpPort()

Method Summary

void	checkArgs(String argStr) Verify that the argument, if given, in the conf is parseable.
boolean	tryFence(HAServiceTarget target, String argsStr) Attempt to fence the target node.

Methods inherited from class org.apache.hadoop.conf.Configured

getConf, setConf

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SshFenceByTcpPort

public SshFenceByTcpPort()

Method Detail

checkArgs

public void checkArgs(String argStr)
               throws BadFencingConfigurationException

Verify that the argument, if given, in the conf is parseable.

Specified by:

checkArgs in interface FenceMethod

Parameters:

argStr - the arguments provided in the configuration. This may be null if the operator did not configure any arguments.

Throws:

BadFencingConfigurationException - if the arguments are invalid

tryFence

public boolean tryFence(HAServiceTarget target,
                        String argsStr)
                 throws BadFencingConfigurationException

Description copied from interface: FenceMethod

Attempt to fence the target node.

Specified by:

tryFence in interface FenceMethod

argsStr - the configured arguments, which were checked at startup by FenceMethod.checkArgs(String)

Returns:

true if fencing was successful, false if unsuccessful or indeterminate

Throws:

BadFencingConfigurationException - if the configuration was determined to be invalid only at runtime