org.apache.slider.server.services.workflow

Class WorkflowSequenceService

java.lang.Object

org.apache.hadoop.service.AbstractService

org.apache.slider.server.services.workflow.WorkflowSequenceService

All Implemented Interfaces:

Closeable, AutoCloseable, org.apache.hadoop.service.Service, org.apache.hadoop.service.ServiceStateChangeListener, ServiceParent

Direct Known Subclasses:

AbstractProviderService

public class WorkflowSequenceService
extends org.apache.hadoop.service.AbstractService
implements ServiceParent, org.apache.hadoop.service.ServiceStateChangeListener

This resembles the YARN CompositeService, except that it starts one service after another Workflow

1. When the WorkflowSequenceService instance is initialized, it only initializes itself.
2. When the WorkflowSequenceService instance is started, it initializes then starts the first of its children. If there are no children, it immediately stops.
3. When the active child stops, it did not fail, and the parent has not stopped -then the next service is initialized and started. If there is no remaining child the parent service stops.
4. If the active child did fail, the parent service notes the exception and stops -effectively propagating up the failure.

New service instances MAY be added to a running instance -but no guarantees can be made as to whether or not they will be run.

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
WorkflowSequenceService() Construct an instance with the default name
WorkflowSequenceService(String name) Construct an instance
WorkflowSequenceService(String name, List<org.apache.hadoop.service.Service> children) Create a service sequence with the given list of services
WorkflowSequenceService(String name, org.apache.hadoop.service.Service... children) Create a service sequence with the given list of services

Method Summary

Methods

Modifier and Type	Method and Description
void	addService(org.apache.hadoop.service.Service service) Add the passed Service to the list of services managed by this WorkflowSequenceService
org.apache.hadoop.service.Service	getActiveService() Get the current service -which may be null
org.apache.hadoop.service.Service	getPreviousService() Get the previously active service
List<org.apache.hadoop.service.Service>	getServices() Get an unmodifiable list of services
protected void	onServiceCompleted(org.apache.hadoop.service.Service service) handler for service completion: base class starts the next service
protected void	serviceStart() When started
protected void	serviceStop()
protected void	setStopIfNoChildServicesAtStartup(boolean stopIfNoChildServicesAtStartup)
boolean	startNextService() Start the next service in the list.
void	stateChanged(org.apache.hadoop.service.Service service) State change event relays service stop events to onServiceCompleted(Service).
String	toString()

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, unregisterGlobalListener, unregisterServiceListener, waitForServiceToStop

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.hadoop.service.Service

close, getBlockers, getConfig, getFailureCause, getFailureState, getLifecycleHistory, getName, getServiceState, getStartTime, init, isInState, registerServiceListener, start, stop, unregisterServiceListener, waitForServiceToStop

Constructor Detail

WorkflowSequenceService

public WorkflowSequenceService(String name)

Construct an instance

Parameters:

name - service name

WorkflowSequenceService

public WorkflowSequenceService()

Construct an instance with the default name

WorkflowSequenceService

public WorkflowSequenceService(String name,
                       org.apache.hadoop.service.Service... children)

Create a service sequence with the given list of services

Parameters:

name - service name

children - initial sequence

WorkflowSequenceService

public WorkflowSequenceService(String name,
                       List<org.apache.hadoop.service.Service> children)

Create a service sequence with the given list of services

Parameters:

name - service name

children - initial sequence

Method Detail

getActiveService

public org.apache.hadoop.service.Service getActiveService()

Get the current service -which may be null

Returns:

service running

getPreviousService

public org.apache.hadoop.service.Service getPreviousService()

Get the previously active service

Returns:

the service last run, or null if there is none.

setStopIfNoChildServicesAtStartup

protected void setStopIfNoChildServicesAtStartup(boolean stopIfNoChildServicesAtStartup)

serviceStart

protected void serviceStart()
                     throws Exception

When started

Overrides:

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

Throws:

Exception

serviceStop

protected void serviceStop()
                    throws Exception

Overrides:

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

Throws:

Exception

startNextService

public boolean startNextService()

Start the next service in the list. Return false if there are no more services to run, or this service has stopped

Returns:

true if a service was started

Throws:

RuntimeException - from any init or start failure

org.apache.hadoop.service.ServiceStateException - if this call is made before the service is started

stateChanged

public void stateChanged(org.apache.hadoop.service.Service service)

State change event relays service stop events to onServiceCompleted(Service). Subclasses can extend that with extra logic

Specified by:

stateChanged in interface org.apache.hadoop.service.ServiceStateChangeListener

Parameters:

service - the service that has changed.

onServiceCompleted

protected void onServiceCompleted(org.apache.hadoop.service.Service service)

handler for service completion: base class starts the next service

Parameters:

service - service that has completed

addService

public void addService(org.apache.hadoop.service.Service service)

Add the passed Service to the list of services managed by this WorkflowSequenceService

Specified by:

addService in interface ServiceParent

Parameters:

service - the Service to be added

getServices

public List<org.apache.hadoop.service.Service> getServices()

Get an unmodifiable list of services

Specified by:

getServices in interface ServiceParent

Returns:

a list of child services at the time of invocation - added services will not be picked up.

toString

public String toString()

Overrides:

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