Service (Apache Hadoop Main 3.4.2 API)

All Superinterfaces:

AutoCloseable, Closeable

All Known Subinterfaces:

DNSOperations, LaunchableService, RegistryOperations

All Known Implementing Classes:

AbstractLaunchableService, AbstractLivelinessMonitor, AbstractService, AddingCompositeService, AHSClient, AMRMClient, AMRMClientAsync, AppAdminClient, AsyncDispatcher, CompositeService, org.apache.hadoop.registry.client.impl.zk.CuratorService, HistoryFileManager, NMClient, NMClientAsync, RegistryOperationsClient, RegistryOperationsService, ServiceClient, SharedCacheClient, TimelineClient, TimelineReaderClient, TimelineReaderClientImpl, YarnClient
```
@InterfaceAudience.Public
 @InterfaceStability.Evolving
public interface Service
extends Closeable
```
Service LifeCycle.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method and Description
`void`	`close()` A version of stop() that is designed to be usable in Java7 closure clauses.
`Map<String,String>`	`getBlockers()` Get the blockers on a service -remote dependencies that are stopping the service from being live.
`Configuration`	`getConfig()` Get the configuration of this service.
`Throwable`	`getFailureCause()` Get the first exception raised during the service failure.
`org.apache.hadoop.service.Service.STATE`	`getFailureState()` Get the state in which the failure in `getFailureCause()` occurred.
`List<LifecycleEvent>`	`getLifecycleHistory()` Get a snapshot of the lifecycle history; it is a static list
`String`	`getName()` Get the name of this service.
`org.apache.hadoop.service.Service.STATE`	`getServiceState()` Get the current service state
`long`	`getStartTime()` Get the service start time
`void`	`init(Configuration config)` Initialize the service.
`boolean`	`isInState(org.apache.hadoop.service.Service.STATE state)` Query to see if the service is in a specific state.
`void`	`registerServiceListener(ServiceStateChangeListener listener)` Register a listener to the service state change events.
`void`	`start()` Start the service.
`void`	`stop()` Stop the service.
`void`	`unregisterServiceListener(ServiceStateChangeListener listener)` Unregister a previously registered listener of the service state change events.
`boolean`	`waitForServiceToStop(long timeout)` Block waiting for the service to stop; uses the termination notification object to do so.

- Method Detail
  - init
```
void init(Configuration config)
```
    Initialize the service. The transition MUST be from Service.STATE.NOTINITED to Service.STATE.INITED unless the operation failed and an exception was raised, in which case stop() MUST be invoked and the service enter the state Service.STATE.STOPPED.
    
    Parameters:
    
    config - the configuration of the service
    
    Throws:
    
    RuntimeException - on any failure during the operation
  - start
```
void start()
```
    Start the service. The transition MUST be from Service.STATE.INITED to Service.STATE.STARTED unless the operation failed and an exception was raised, in which case stop() MUST be invoked and the service enter the state Service.STATE.STOPPED.
    
    Throws:
    
    RuntimeException - on any failure during the operation
  - stop
```
void stop()
```
    Stop the service. This MUST be a no-op if the service is already in the Service.STATE.STOPPED state. It SHOULD be a best-effort attempt to stop all parts of the service. The implementation must be designed to complete regardless of the service state, including the initialized/uninitialized state of all its internal fields.
    
    Throws:
    
    RuntimeException - on any failure during the stop operation
  - close
```
void close()
    throws IOException
```
    A version of stop() that is designed to be usable in Java7 closure clauses. Implementation classes MUST relay this directly to stop()
    
    Specified by:
    
    close in interface AutoCloseable
    
    Specified by:
    
    close in interface Closeable
    
    Throws:
    
    IOException - never
    
    RuntimeException - on any failure during the stop operation
  - registerServiceListener
```
void registerServiceListener(ServiceStateChangeListener listener)
```
    Register a listener to the service state change events. If the supplied listener is already listening to this service, this method is a no-op.
    
    Parameters:
    
    listener - a new listener
  - unregisterServiceListener
```
void unregisterServiceListener(ServiceStateChangeListener listener)
```
    Unregister a previously registered listener of the service state change events. No-op if the listener is already unregistered.
    
    Parameters:
    
    listener - the listener to unregister.
  - getName
```
String getName()
```
    Get the name of this service.
    
    Returns:
    
    the service name
  - getConfig
```
Configuration getConfig()
```
    Get the configuration of this service. This is normally not a clone and may be manipulated, though there are no guarantees as to what the consequences of such actions may be
    
    Returns:
    
    the current configuration, unless a specific implentation chooses otherwise.
  - getServiceState
```
org.apache.hadoop.service.Service.STATE getServiceState()
```
    Get the current service state
    
    Returns:
    
    the state of the service
  - getStartTime
```
long getStartTime()
```
    Get the service start time
    
    Returns:
    
    the start time of the service. This will be zero if the service has not yet been started.
  - isInState
```
boolean isInState(org.apache.hadoop.service.Service.STATE state)
```
    Query to see if the service is in a specific state. In a multi-threaded system, the state may not hold for very long.
    
    Parameters:
    
    state - the expected state
    
    Returns:
    
    true if, at the time of invocation, the service was in that state.
  - getFailureCause
```
Throwable getFailureCause()
```
    Get the first exception raised during the service failure. If null, no exception was logged
    
    Returns:
    
    the failure logged during a transition to the stopped state
  - getFailureState
```
org.apache.hadoop.service.Service.STATE getFailureState()
```
    Get the state in which the failure in getFailureCause() occurred.
    
    Returns:
    
    the state or null if there was no failure
  - waitForServiceToStop
```
boolean waitForServiceToStop(long timeout)
```
    Block waiting for the service to stop; uses the termination notification object to do so. This method will only return after all the service stop actions have been executed (to success or failure), or the timeout elapsed This method can be called before the service is inited or started; this is to eliminate any race condition with the service stopping before this event occurs.
    
    Parameters:
    
    timeout - timeout in milliseconds. A value of zero means "forever"
    
    Returns:
    
    true iff the service stopped in the time period
  - getLifecycleHistory
```
List<LifecycleEvent> getLifecycleHistory()
```
    Get a snapshot of the lifecycle history; it is a static list
    
    Returns:
    
    a possibly empty but never null list of lifecycle events.
  - getBlockers
```
Map<String,String> getBlockers()
```
    Get the blockers on a service -remote dependencies that are stopping the service from being live.
    
    Returns:
    
    a (snapshotted) map of blocker name->description values

Interface Service

Method Summary

Method Detail

init

start

stop

close

registerServiceListener

unregisterServiceListener

getName

getConfig

getServiceState

getStartTime

isInState

getFailureCause

getFailureState

waitForServiceToStop

getLifecycleHistory

getBlockers