org.apache.hadoop.hbase.procedure2

Class StateMachineProcedure<TEnvironment,TState>

java.lang.Object

org.apache.hadoop.hbase.procedure2.Procedure<TEnvironment>

org.apache.hadoop.hbase.procedure2.StateMachineProcedure<TEnvironment,TState>

All Implemented Interfaces:

Comparable<Procedure<TEnvironment>>

Direct Known Subclasses:

AbstractPeerProcedure, AbstractStateMachineNamespaceProcedure, AbstractStateMachineTableProcedure, RecoverMetaProcedure, ServerCrashProcedure, SplitWALProcedure, SwitchRpcThrottleProcedure

@InterfaceAudience.Private
 @InterfaceStability.Evolving
public abstract class StateMachineProcedure<TEnvironment,TState>
extends Procedure<TEnvironment>

Procedure described by a series of steps.

The procedure implementor must have an enum of 'states', describing the various step of the procedure. Once the procedure is running, the procedure-framework will call executeFromState() using the 'state' provided by the user. The first call to executeFromState() will be performed with 'state = null'. The implementor can jump between states using setNextState(MyStateEnum.ordinal()). The rollback will call rollbackState() for each state that was executed, in reverse order.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	StateMachineProcedure.Flow

Nested classes/interfaces inherited from class org.apache.hadoop.hbase.procedure2.Procedure

Procedure.LockState

Field Summary

Fields

Modifier and Type	Field and Description
private AtomicBoolean	aborted
private int	cycles Cycles on same state.
private static int	EOF_STATE
private static org.slf4j.Logger	LOG
private int	previousState Ordinal of the previous state.
private int	stateCount
private StateMachineProcedure.Flow	stateFlow
private int[]	states
private List<Procedure<TEnvironment>>	subProcList

Fields inherited from class org.apache.hadoop.hbase.procedure2.Procedure

NO_PROC_ID, NO_TIMEOUT

Constructor Summary

Constructors

Constructor and Description
StateMachineProcedure()

Method Summary

Modifier and Type	Method and Description
protected boolean	abort(TEnvironment env) The abort() call is asynchronous and each procedure must decide how to deal with it, if they want to be abortable.
protected <T extends Procedure<TEnvironment>> void	addChildProcedure(T... subProcedure) Add a child procedure to execute
protected void	deserializeStateData(ProcedureStateSerializer serializer) Called on store load to allow the user to decode the previously serialized state.
protected Procedure[]	execute(TEnvironment env) The main code of the procedure.
protected abstract StateMachineProcedure.Flow	executeFromState(TEnvironment env, TState state) called to perform a single step of the specified 'state' of the procedure
protected void	failIfAborted() If procedure has more states then abort it otherwise procedure is finished and abort can be ignored.
protected TState	getCurrentState()
int	getCurrentStateId() This method is used from test code as it cannot be assumed that state transition will happen sequentially.
protected int	getCycles()
protected abstract TState	getInitialState() Return the initial state object that will be used for the first call to executeFromState().
protected abstract TState	getState(int stateId) Convert an ordinal (or state id) to an Enum (or more descriptive) state object.
protected abstract int	getStateId(TState state) Convert the Enum (or more descriptive) state object to an ordinal (or state id).
private boolean	hasMoreState()
private boolean	isEofState()
protected boolean	isRollbackSupported(TState state) Used by the default implementation of abort() to know if the current state can be aborted and rollback can be triggered.
protected boolean	isYieldAfterExecutionStep(TEnvironment env) By default, the procedure framework/executor will try to run procedures start to finish.
protected boolean	isYieldBeforeExecuteFromState(TEnvironment env, TState state) By default, the executor will try ro run all the steps of the procedure start to finish.
protected void	rollback(TEnvironment env) The code to undo what was done by the execute() code.
protected abstract void	rollbackState(TEnvironment env, TState state) called to perform the rollback of the specified state
protected void	serializeStateData(ProcedureStateSerializer serializer) The user-level code of the procedure may have some state to persist (e.g.
private void	setNextState(int stateId) Set the next state for the procedure.
protected void	setNextState(TState state) Set the next state for the procedure.
protected void	toStringState(StringBuilder builder) Called from Procedure.toString() when interpolating Procedure State.

Methods inherited from class org.apache.hadoop.hbase.procedure2.Procedure

acquireLock, addStackIndex, afterReplay, beforeReplay, bypass, compareTo, completionCleanup, doAcquireLock, doExecute, doReleaseLock, doRollback, elapsedTime, getChildrenLatch, getException, getLastUpdate, getNonceKey, getOwner, getParentProcId, getProcedureMetrics, getProcId, getProcIdHashCode, getProcName, getResult, getRootProcedureId, getRootProcId, getStackIndexes, getState, getSubmittedTime, getTimeout, getTimeoutTimestamp, hasChildren, hasException, hasLock, hasOwner, hasParent, hasTimeout, haveSameParent, holdLock, incChildrenLatch, isBypass, isFailed, isFinished, isInitializing, isLockedWhenLoading, isRunnable, isSuccess, isWaiting, lockedWhenLoading, needPersistence, releaseLock, removeStackIndex, resetPersistence, restoreLock, setAbortFailure, setChildrenLatch, setFailure, setFailure, setLastUpdate, setNonceKey, setOwner, setOwner, setParentProcId, setProcId, setResult, setRootProcId, setStackIndexes, setState, setSubmittedTime, setTimeout, setTimeoutFailure, shouldWaitClientAck, skipPersistence, toString, toStringClass, toStringClassDetails, toStringDetails, toStringSimpleSB, tryRunnable, updateMetricsOnFinish, updateMetricsOnSubmit, updateTimestamp, waitInitialized, wasExecuted

Methods inherited from class java.lang.Object

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

Field Detail

LOG

private static final org.slf4j.Logger LOG

EOF_STATE

private static final int EOF_STATE

See Also:

Constant Field Values

aborted

private final AtomicBoolean aborted

stateFlow

private StateMachineProcedure.Flow stateFlow

stateCount

private int stateCount

states

private int[] states

subProcList

private List<Procedure<TEnvironment>> subProcList

cycles

private int cycles

Cycles on same state. Good for figuring if we are stuck.

previousState

private int previousState

Ordinal of the previous state. So we can tell if we are progressing or not.

Constructor Detail

StateMachineProcedure

public StateMachineProcedure()

Method Detail

getCycles

protected final int getCycles()

executeFromState

protected abstract StateMachineProcedure.Flow executeFromState(TEnvironment env,
                                                               TState state)
                                                        throws ProcedureSuspendedException,
                                                               ProcedureYieldException,
                                                               InterruptedException

called to perform a single step of the specified 'state' of the procedure

Parameters:

state - state to execute

Returns:

Flow.NO_MORE_STATE if the procedure is completed, Flow.HAS_MORE_STATE if there is another step.

Throws:

ProcedureSuspendedException

ProcedureYieldException

InterruptedException

rollbackState

protected abstract void rollbackState(TEnvironment env,
                                      TState state)
                               throws IOException,
                                      InterruptedException

called to perform the rollback of the specified state

Parameters:

state - state to rollback

Throws:

IOException - temporary failure, the rollback will retry later

InterruptedException

getState

protected abstract TState getState(int stateId)

Convert an ordinal (or state id) to an Enum (or more descriptive) state object.

Parameters:

stateId - the ordinal() of the state enum (or state id)

Returns:

the state enum object

getStateId

protected abstract int getStateId(TState state)

Convert the Enum (or more descriptive) state object to an ordinal (or state id).

Parameters:

state - the state enum object

Returns:

stateId the ordinal() of the state enum (or state id)

getInitialState

protected abstract TState getInitialState()

Return the initial state object that will be used for the first call to executeFromState().

Returns:

the initial state enum object

setNextState

protected void setNextState(TState state)

Set the next state for the procedure.

Parameters:

state - the state enum object

isYieldBeforeExecuteFromState

protected boolean isYieldBeforeExecuteFromState(TEnvironment env,
                                                TState state)

By default, the executor will try ro run all the steps of the procedure start to finish. Return true to make the executor yield between execution steps to give other procedures time to run their steps.

Parameters:

state - the state we are going to execute next.

Returns:

Return true if the executor should yield before the execution of the specified step. Defaults to return false.

addChildProcedure

protected <T extends Procedure<TEnvironment>> void addChildProcedure(T... subProcedure)

Add a child procedure to execute

Parameters:

subProcedure - the child procedure

execute

protected Procedure[] execute(TEnvironment env)
                       throws ProcedureSuspendedException,
                              ProcedureYieldException,
                              InterruptedException

Description copied from class: Procedure

The main code of the procedure. It must be idempotent since execute() may be called multiple times in case of machine failure in the middle of the execution.

Specified by:

execute in class Procedure<TEnvironment>

Parameters:

env - the environment passed to the ProcedureExecutor

Returns:

a set of sub-procedures to run or ourselves if there is more work to do or null if the procedure is done.

Throws:

ProcedureSuspendedException - Signal to the executor that Procedure has suspended itself and has set itself up waiting for an external event to wake it back up again.

ProcedureYieldException - the procedure will be added back to the queue and retried later.

InterruptedException - the procedure will be added back to the queue and retried later.

rollback

protected void rollback(TEnvironment env)
                 throws IOException,
                        InterruptedException

Description copied from class: Procedure

The code to undo what was done by the execute() code. It is called when the procedure or one of the sub-procedures failed or an abort was requested. It should cleanup all the resources created by the execute() call. The implementation must be idempotent since rollback() may be called multiple time in case of machine failure in the middle of the execution.

Specified by:

rollback in class Procedure<TEnvironment>

Parameters:

env - the environment passed to the ProcedureExecutor

Throws:

IOException - temporary failure, the rollback will retry later

InterruptedException - the procedure will be added back to the queue and retried later

isEofState

private boolean isEofState()

abort

protected boolean abort(TEnvironment env)

Description copied from class: Procedure

The abort() call is asynchronous and each procedure must decide how to deal with it, if they want to be abortable. The simplest implementation is to have an AtomicBoolean set in the abort() method and then the execute() will check if the abort flag is set or not. abort() may be called multiple times from the client, so the implementation must be idempotent.

NOTE: abort() is not like Thread.interrupt(). It is just a notification that allows the procedure implementor abort.

Specified by:

abort in class Procedure<TEnvironment>

failIfAborted

protected final void failIfAborted()

If procedure has more states then abort it otherwise procedure is finished and abort can be ignored.

isRollbackSupported

protected boolean isRollbackSupported(TState state)

Used by the default implementation of abort() to know if the current state can be aborted and rollback can be triggered.

isYieldAfterExecutionStep

protected boolean isYieldAfterExecutionStep(TEnvironment env)

Description copied from class: Procedure

By default, the procedure framework/executor will try to run procedures start to finish. Return true to make the executor yield between each execution step to give other procedures a chance to run.

Overrides:

isYieldAfterExecutionStep in class Procedure<TEnvironment>

Parameters:

env - the environment passed to the ProcedureExecutor

Returns:

Return true if the executor should yield on completion of an execution step. Defaults to return false.

hasMoreState

private boolean hasMoreState()

getCurrentState

protected TState getCurrentState()

getCurrentStateId

public int getCurrentStateId()

This method is used from test code as it cannot be assumed that state transition will happen sequentially. Some procedures may skip steps/ states, some may add intermediate steps in future.

setNextState

private void setNextState(int stateId)

Set the next state for the procedure.

Parameters:

stateId - the ordinal() of the state enum (or state id)

toStringState

protected void toStringState(StringBuilder builder)

Description copied from class: Procedure

Called from Procedure.toString() when interpolating Procedure State. Allows decorating generic Procedure State with Procedure particulars.

Overrides:

toStringState in class Procedure<TEnvironment>

Parameters:

builder - Append current ProcedureProtos.ProcedureState

serializeStateData

protected void serializeStateData(ProcedureStateSerializer serializer)
                           throws IOException

Description copied from class: Procedure

The user-level code of the procedure may have some state to persist (e.g. input arguments or current position in the processing state) to be able to resume on failure.

Specified by:

serializeStateData in class Procedure<TEnvironment>

Parameters:

serializer - stores the serializable state

Throws:

IOException

deserializeStateData

protected void deserializeStateData(ProcedureStateSerializer serializer)
                             throws IOException

Description copied from class: Procedure

Called on store load to allow the user to decode the previously serialized state.

Specified by:

deserializeStateData in class Procedure<TEnvironment>

Parameters:

serializer - contains the serialized state

Throws:

IOException