org.neo4j.kernel.lifecycle

Class SafeLifecycle

java.lang.Object

org.neo4j.kernel.lifecycle.SafeLifecycle

All Implemented Interfaces:

Lifecycle

public abstract class SafeLifecycle
extends Object
implements Lifecycle

A safer lifecycle adapter with strict semantics and as a result simpler error handling and reasoning. If the semantics of this class is not consistent with what you are after, then it is probably better to create a new adapter with the specific semantics required.

 Guide

  *: No-op    (will not invoke operation)
  -: Error    (will throw IllegalStateException)

  P: PRE      ("pre init")
  I: IDLE     ("initialized" or "stopped")
  R: RUN      ("started")
  H: HALT     ("shutdown")
 

A successful operation is an operation not throwing an exception.

End states on a successful operation.

  ---------------------------------------------------
 | FROM \ op |  init()  start()  stop()  shutdown()  |
  ---------------------------------------------------
 | PRE       |   IDLE      -       -       HALT(*)   |
 | IDLE      |    -       RUN    IDLE(*)    HALT     |
 | RUN       |    -        -      IDLE       -       |
 | HALT      |    -        -       -         -       |
  ---------------------------------------------------
 

End states on a failed operation.

  ---------------------------------------------------
 | FROM \ op |  init()  start()  stop()  shutdown()  |
  ---------------------------------------------------
 | PRE       |   PRE       -       -       HALT(*)   |
 | IDLE      |    -       IDLE   IDLE(*)    HALT     |
 | RUN       |    -        -      IDLE       -       |
 | HALT      |    -        -       -         -       |
  ---------------------------------------------------
 

A few notes:

• will not invoke stop0() if start0() wasn't successful
• will not invoke shutdown0() if init0() wasn't successful

The expectation with regards to error handling and cleanup is that an unclean start() is cleaned up by the start0() method and thus the component is left in IDLE. The same goes for issues happening during init0(), which leaves the component in PRE.

Because of the way that LifeSupport operates today, this class will ignore stop() calls made while in IDLE. Similarly, calls to shutdown() will be ignored while in PRE. This allows this class to be managed by a LifeSupport without throwing IllegalStateException on those state transitions, which otherwise would have been disallowed and handled in the same way as other illegal state transitions.

This adapter will not allow a shutdown lifecycle to be reinitialized and started again.

Nested Class Summary

Nested classes/interfaces inherited from interface org.neo4j.kernel.lifecycle.Lifecycle

Lifecycle.Delegate

Method Summary

Modifier and Type	Method and Description
void	init()
void	init0()
void	shutdown()
void	shutdown0()
void	start()
void	start0()
org.neo4j.kernel.lifecycle.SafeLifecycle.State	state()
void	stop()
void	stop0()

Methods inherited from class java.lang.Object

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

Method Detail

init

public final void init()
                throws Throwable

Specified by:

init in interface Lifecycle

Throws:

Throwable

start

public final void start()
                 throws Throwable

Specified by:

start in interface Lifecycle

Throws:

Throwable

stop

public final void stop()
                throws Throwable

Specified by:

stop in interface Lifecycle

Throws:

Throwable

shutdown

public final void shutdown()
                    throws Throwable

Specified by:

shutdown in interface Lifecycle

Throws:

Throwable

init0

public void init0()
           throws Throwable

Throws:

Throwable

start0

public void start0()
            throws Throwable

Throws:

Throwable

stop0

public void stop0()
           throws Throwable

Throws:

Throwable

shutdown0

public void shutdown0()
               throws Throwable

Throws:

Throwable

state

public org.neo4j.kernel.lifecycle.SafeLifecycle.State state()