org.apache.slider.server.services.workflow

Class ForkedProcessService

java.lang.Object

org.apache.hadoop.service.AbstractService

org.apache.slider.server.services.workflow.WorkflowExecutorService<ExecutorService>

org.apache.slider.server.services.workflow.ForkedProcessService

All Implemented Interfaces:

Closeable, AutoCloseable, Runnable, org.apache.hadoop.service.Service, LongLivedProcessLifecycleEvent

public class ForkedProcessService
extends WorkflowExecutorService<ExecutorService>
implements LongLivedProcessLifecycleEvent, Runnable

Service wrapper for an external program that is launched and can/will terminate. This service is notified when the subprocess terminates, and stops itself and converts a non-zero exit code into a failure exception.

Key Features:

1. The property executionTimeout can be set to set a limit on the duration of a process
2. Output is streamed to the output logger provided
.
3. The most recent lines of output are saved to a linked list
.
4. A synchronous callback, LongLivedProcessLifecycleEvent, is raised on the start and finish of a process.

Usage:

The service can be built in the constructor, ForkedProcessService(String, Map, List), or have its simple constructor used to instantiate the service, then the build(Map, List) command used to define the environment variables and list of commands to execute. One of these two options MUST be exercised before calling the services's AbstractService.start() method.

The forked process is executed in the service's serviceStart() method; if still running when the service is stopped, serviceStop() will attempt to stop it.

The service delegates process execution to LongLivedProcess, receiving callbacks via the LongLivedProcessLifecycleEvent. When the service receives a callback notifying that the process has completed, it calls its AbstractService.stop() method. If the error code was non-zero, the service is logged as having failed.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.hadoop.service.Service

org.apache.hadoop.service.Service.STATE

Constructor Summary

Constructors

Constructor and Description
ForkedProcessService(String name) Create an instance of the service
ForkedProcessService(String name, Map<String,String> env, List<String> commandList) Create an instance of the service, set up the process

Method Summary

Methods

Modifier and Type	Method and Description
void	build(Map<String,String> env, List<String> commandList) Build the process to execute when the service is started
protected void	completed() Note the process as having completed.
Integer	getExitCode()
int	getExitCodeSignCorrected()
List<String>	getRecentOutput() Get the recent output from the process, or [] if not defined
List<String>	getRecentOutput(boolean finalOutput, int duration) Get the recent output from the process, or [] if not defined
boolean	isProcessRunning() Is a process running: between started and terminated
boolean	isProcessStarted()
boolean	isProcessTerminated()
void	onProcessExited(LongLivedProcess process, int uncorrected, int code) Callback when a process has finished
void	onProcessStarted(LongLivedProcess process) Callback when a process is started
void	run() handle timeout response by escalating it to a failure
protected void	serviceStart()
protected void	serviceStop() Stop the service: halt the executor.
void	setProcessLog(org.slf4j.Logger processLog) Set the process log.
void	setTimeout(int timeout, int code) Set the timeout by which time a process must have finished -or -1 for forever

Methods inherited from class org.apache.slider.server.services.workflow.WorkflowExecutorService

execute, getExecutor, setExecutor, stopExecutor, submit

Methods inherited from class org.apache.hadoop.service.AbstractService

close, getBlockers, getConfig, getFailureCause, getFailureState, getLifecycleHistory, getName, getServiceState, getStartTime, init, isInState, noteFailure, putBlocker, registerGlobalListener, registerServiceListener, removeBlocker, serviceInit, setConfig, start, stop, toString, unregisterGlobalListener, unregisterServiceListener, waitForServiceToStop

Methods inherited from class java.lang.Object

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

Constructor Detail

ForkedProcessService

public ForkedProcessService(String name)

Create an instance of the service

Parameters:

name - a name

ForkedProcessService

public ForkedProcessService(String name,
                    Map<String,String> env,
                    List<String> commandList)
                     throws IOException

Create an instance of the service, set up the process

Parameters:

name - a name

commandList - list of commands is inserted on the front

env - environment variables above those generated by

Throws:

IOException - IO problems

Method Detail

serviceStart

protected void serviceStart()
                     throws Exception

Overrides:

serviceStart in class org.apache.hadoop.service.AbstractService

Throws:

Exception

serviceStop

protected void serviceStop()
                    throws Exception

Description copied from class: WorkflowExecutorService

Stop the service: halt the executor.

Overrides:

serviceStop in class WorkflowExecutorService<ExecutorService>

Throws:

Exception - exception.

setProcessLog

public void setProcessLog(org.slf4j.Logger processLog)

Set the process log. This may be null for "do not log"

Parameters:

processLog - process log

setTimeout

public void setTimeout(int timeout,
              int code)

Set the timeout by which time a process must have finished -or -1 for forever

Parameters:

timeout - timeout in milliseconds

build

public void build(Map<String,String> env,
         List<String> commandList)
           throws IOException

Build the process to execute when the service is started

Parameters:

commandList - list of commands is inserted on the front

env - environment variables above those generated by

Throws:

IOException - IO problems

onProcessStarted

public void onProcessStarted(LongLivedProcess process)

Description copied from interface: LongLivedProcessLifecycleEvent

Callback when a process is started

Specified by:

onProcessStarted in interface LongLivedProcessLifecycleEvent

Parameters:

process - the process invoking the callback

onProcessExited

public void onProcessExited(LongLivedProcess process,
                   int uncorrected,
                   int code)

Description copied from interface: LongLivedProcessLifecycleEvent

Callback when a process has finished

Specified by:

onProcessExited in interface LongLivedProcessLifecycleEvent

Parameters:

process - the process invoking the callback

uncorrected - exit code from the process

code - the code- as sign corrected

run

public void run()

handle timeout response by escalating it to a failure

Specified by:

run in interface Runnable

completed

protected void completed()

Note the process as having completed. The process marked as terminated -and anything synchronized on processTerminated is notified

isProcessTerminated

public boolean isProcessTerminated()

isProcessStarted

public boolean isProcessStarted()

isProcessRunning

public boolean isProcessRunning()

Is a process running: between started and terminated

Returns:

true if the process is up.

getExitCode

public Integer getExitCode()

getExitCodeSignCorrected

public int getExitCodeSignCorrected()

getRecentOutput

public List<String> getRecentOutput()

Get the recent output from the process, or [] if not defined

Returns:

a possibly empty list

getRecentOutput

public List<String> getRecentOutput(boolean finalOutput,
                           int duration)

Get the recent output from the process, or [] if not defined

Parameters:

finalOutput - flag to indicate "wait for the final output of the process"

duration - the duration, in ms, to wait for recent output to become non-empty

Returns:

a possibly empty list