Package org.apache.hadoop.ha

Class ShellCommandFencer

java.lang.Object

org.apache.hadoop.conf.Configured

org.apache.hadoop.ha.ShellCommandFencer

All Implemented Interfaces:

Configurable, FenceMethod

public class ShellCommandFencer
extends Configured
implements FenceMethod

Fencing method that runs a shell command. It should be specified in the fencing configuration like:
shell(/path/to/my/script.sh arg1 arg2 ...)
The string between '(' and ')' is passed directly to a bash shell (cmd.exe on Windows) and may not include any closing parentheses.

The shell command will be run with an environment set up to contain all of the current Hadoop configuration variables, with the '_' character replacing any '.' or '-' characters in the configuration keys.

If the shell command returns an exit code of 0, the fencing is determined to be successful. If it returns any other exit code, the fencing was not successful and the next fencing method in the list will be attempted.

Note: this fencing method does not implement any timeout. If timeouts are necessary, they should be implemented in the shell script itself (eg by forking a subshell to kill its parent in some number of seconds).

Constructor Summary

Constructors

Constructor	Description
ShellCommandFencer()

Method Summary

Modifier and Type	Method	Description
void	checkArgs(String args)	Verify that the given fencing method's arguments are valid.
boolean	tryFence(HAServiceTarget target, String args)	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 Details

ShellCommandFencer

public ShellCommandFencer()

Method Details

checkArgs

public void checkArgs(String args)
               throws BadFencingConfigurationException

Description copied from interface: FenceMethod

Verify that the given fencing method's arguments are valid.

Specified by:

checkArgs in interface FenceMethod

Parameters:

args - 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 args)

Description copied from interface: FenceMethod

Attempt to fence the target node.

Specified by:

tryFence in interface FenceMethod

Parameters:

target - the target of the service to fence

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

Returns:

true if fencing was successful, false if unsuccessful or indeterminate