org.apache.slider.server.services.workflow

Class LongLivedProcess

java.lang.Object

org.apache.slider.server.services.workflow.LongLivedProcess

All Implemented Interfaces:

Runnable

public class LongLivedProcess
extends Object
implements Runnable

Execute a long-lived process.

Hadoop's Shell class assumes it is executing a short lived application; this class allows for the process to run for the life of the Java process that forked it. It is designed to be embedded inside a YARN service, though this is not the sole way that it can be used

Key Features:

1. Output is streamed to the output logger provided
.
2. the input stream is closed as soon as the process starts.
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.

Field Summary

Fields

Modifier and Type	Field and Description
static int	RECENT_LINE_LOG_LIMIT Limit on number of lines to retain in the "recent" line list:64

Constructor Summary

Constructors

Constructor and Description
LongLivedProcess(String name, org.slf4j.Logger processLog, List<String> commands) Create an instance

Method Summary

Methods

Modifier and Type	Method and Description
protected String	describeBuilder() Get a text description of the builder suitable for log output
void	dumpEnv(StringBuilder buffer) Dump the environment to a string builder
String	getCommand()
List<String>	getCommands() Get the command list
String	getEnv(String variable) Get the process environment
Integer	getExitCode() Get the exit code: null until the process has finished
Integer	getExitCodeSignCorrected() Get the exit code sign corrected: null until the process has finished
Process	getProcess() Get the process reference
ProcessBuilder	getProcessBuilder() Get the process builder -this can be manipulated up to the start() operation.
List<String>	getRecentOutput() Get the lines of recent output
List<String>	getRecentOutput(boolean finalOutput, int duration) Get the recent output from the process, or [] if not defined
boolean	isFinalOutputProcessed() Query to see if the final output has been processed
boolean	isRecentOutputEmpty()
boolean	isRunning() probe to see if the process is running
void	putEnvMap(Map<String,String> map) Bulk set the environment from a map.
void	run() Entry point for waiting for the program to finish
void	setEnv(String envVar, String val) Add an entry to the environment
void	setLifecycleCallback(LongLivedProcessLifecycleEvent lifecycleCallback) Set an optional application exit callback
void	setProcessLog(org.slf4j.Logger processLog) Set the process log.
void	setRecentLineLimit(int recentLineLimit) Set the limit on recent lines to retain
void	start() Spawn the application
void	stop() Stop the process if it is running.

Methods inherited from class java.lang.Object

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

Field Detail

RECENT_LINE_LOG_LIMIT

public static final int RECENT_LINE_LOG_LIMIT

Limit on number of lines to retain in the "recent" line list:64

See Also:

Constant Field Values

Constructor Detail

LongLivedProcess

public LongLivedProcess(String name,
                org.slf4j.Logger processLog,
                List<String> commands)

Create an instance

Parameters:

name - process name

processLog - log for output (or null)

commands - command list

Method Detail

setRecentLineLimit

public void setRecentLineLimit(int recentLineLimit)

Set the limit on recent lines to retain

Parameters:

recentLineLimit - size of rolling list of recent lines.

setLifecycleCallback

public void setLifecycleCallback(LongLivedProcessLifecycleEvent lifecycleCallback)

Set an optional application exit callback

Parameters:

lifecycleCallback - callback to notify on application exit

setEnv

public void setEnv(String envVar,
          String val)

Add an entry to the environment

Parameters:

envVar - envVar -must not be null

val - value

putEnvMap

public void putEnvMap(Map<String,String> map)

Bulk set the environment from a map. This does not replace the existing environment, just extend it/overwrite single entries.

Parameters:

map - map to add

getEnv

public String getEnv(String variable)

Get the process environment

Parameters:

variable - environment variable

Returns:

the value or null if there is no match

setProcessLog

public void setProcessLog(org.slf4j.Logger processLog)

Set the process log. Ignored once the process starts

Parameters:

processLog - new log ... may be null

getProcess

public Process getProcess()

Get the process reference

Returns:

the process -null if the process is not started

getProcessBuilder

public ProcessBuilder getProcessBuilder()

Get the process builder -this can be manipulated up to the start() operation. As there is no synchronization around it, it must only be used in the same thread setting up the commmand.

Returns:

the process builder

getCommands

public List<String> getCommands()

Get the command list

Returns:

the comands

getCommand

public String getCommand()

isRunning

public boolean isRunning()

probe to see if the process is running

Returns:

true iff the process has been started and is not yet finished

getExitCode

public Integer getExitCode()

Get the exit code: null until the process has finished

Returns:

the exit code or null

getExitCodeSignCorrected

public Integer getExitCodeSignCorrected()

Get the exit code sign corrected: null until the process has finished

Returns:

the exit code or null

stop

public void stop()

Stop the process if it is running. This will trigger an application completion event with the given exit code

describeBuilder

protected String describeBuilder()

Get a text description of the builder suitable for log output

Returns:

a multiline string

dumpEnv

public void dumpEnv(StringBuilder buffer)

Dump the environment to a string builder

Parameters:

buffer - the buffer to append to

run

public void run()

Entry point for waiting for the program to finish

Specified by:

run in interface Runnable

start

public void start()
           throws IOException

Spawn the application

Throws:

IOException - IO problems

getRecentOutput

public List<String> getRecentOutput()

Get the lines of recent output

Returns:

the last few lines of output; an empty list if there are none or the process is not actually running

isRecentOutputEmpty

public boolean isRecentOutputEmpty()

Returns:

whether lines of recent output are empty

isFinalOutputProcessed

public boolean isFinalOutputProcessed()

Query to see if the final output has been processed

Returns:

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, ro wait for recent output to become non-empty

Returns:

a possibly empty list