com.sleepycat.je.txn

Class BuddyLocker

java.lang.Object

com.sleepycat.je.txn.Locker

com.sleepycat.je.txn.BasicLocker

com.sleepycat.je.txn.BuddyLocker

Direct Known Subclasses:

ReadCommittedLocker

public class BuddyLocker
extends BasicLocker

Extends BasicLocker to share locks with another specific locker.

In general, a BuddyLocker can be used whenever the primary (API) locker is in use, and we need to lock a node and release that lock before the primary locker transaction ends. In other words, for this particular lock we don't want to use two-phase locking. To accomplish that we use a separate BuddyLocker instance to hold the lock, while sharing locks with the primary locker. The BuddyLocker can be closed to release this particular lock, without releasing the other locks held by the primary locker.

In particular, a ReadCommittedLocker extends BuddyLocker. The ReadCommittedLocker keeps track of read locks, while its buddy Txn keeps track of write locks. The two lockers must share locks to prevent conflicts.

In addition, a BuddyLocker is used when acquiring a RANGE_INSERT lock. RANGE_INSERT only needs to be held until the point we have inserted the new node into the BIN. A separate locker is therefore used so we can release that lock separately when the insertion into the BIN is complete. But the RANGE_INSERT lock must not conflict with locks held by the primary locker. So a BuddyLocker is used that shares locks with the primary locker.

Field Summary

Fields inherited from class com.sleepycat.je.txn.Locker

afterWaiterHook, envImpl, id, lockManager, thread

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	BuddyLocker(EnvironmentImpl env, Locker buddy) Creates a BuddyLocker.

Method Summary

Modifier and Type	Method and Description
void	checkPreempted(Locker allowPreemptedLocker) Forwards to the parent buddy locker, so the buddy can check itself and all of its child buddies.
static BuddyLocker	createBuddyLocker(EnvironmentImpl env, Locker buddy)
long	getLockTimeout() Returns the lock timeout of the buddy locker, since this locker has no independent timeout.
Transaction	getTransaction() Forwards this call to the buddy locker.
Txn	getTxnLocker() Forwards this call to the buddy locker.
long	getTxnStartMillis() Returns the buddy locker's start time, since this locker has no independent timeout.
long	getTxnTimeout() Returns the transaction timeout of the buddy locker, since this locker has no independent timeout.
boolean	isLocalWrite() Consider this locker local-write if its buddy is local-write.
boolean	isReplicated() Consider this locker replicated if its buddy (Txn) is replicated.
boolean	isTimedOut() Returns whether the buddy locker is timed out, since this locker has no independent timeout.
void	releaseNonTxnLocks() Forwards this call to the base class and to the buddy locker.
void	setLockTimeout(long timeout) Sets the lock timeout of the buddy locker, since this locker has no independent timeout.
void	setOnlyAbortable(OperationFailureException cause) Forwards to the buddy locker, since the buddy may be transactional.
void	setTxnTimeout(long timeout) Sets the transaction timeout of the buddy locker, since this locker has no independent timeout.
boolean	sharesLocksWith(Locker other) Returns whether this locker can share locks with the given locker.

Methods inherited from class com.sleepycat.je.txn.BasicLocker

addDbCleanup, addLock, checkState, collectStats, createBasicLocker, createBasicLocker, generateId, getWriteLockInfo, getWriteOwnerLocker, isReadCommittedIsolation, isSerializableIsolation, isTransactional, lockingRequired, lockInternal, newNonTxnLocker, nonTxnOperationEnd, operationEnd, preLogWithoutLock, registerCursor, unRegisterCursor

Methods inherited from class com.sleepycat.je.txn.Locker

addDeleteInfo, addOpenedDatabase, allowReleaseLockAfterLsnChange, demoteLock, disallowReplicaWrite, dumpLockTable, getDefaultNoWait, getEnvironment, getId, getImportunate, getInitialLockTimeout, getPreemptable, isReadOnly, isReadUncommittedDefault, isRolledBack, isValid, lock, lockAfterLsnChange, nonBlockingLock, openCursorHook, operationEnd, operationEnd, releaseLock, setClosingLocker, setDefaultNoWait, setImportunate, setPreemptable, setPreempted, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

BuddyLocker

protected BuddyLocker(EnvironmentImpl env,
                      Locker buddy)

Creates a BuddyLocker.

Method Detail

createBuddyLocker

public static BuddyLocker createBuddyLocker(EnvironmentImpl env,
                                            Locker buddy)
                                     throws DatabaseException

Throws:

DatabaseException

getTxnLocker

public Txn getTxnLocker()

Forwards this call to the buddy locker. This object itself is never transactional but the buddy may be.

Overrides:

getTxnLocker in class BasicLocker

getTransaction

public Transaction getTransaction()

Forwards this call to the buddy locker. This object itself is never transactional but the buddy may be.

Overrides:

getTransaction in class Locker

releaseNonTxnLocks

public void releaseNonTxnLocks()
                        throws DatabaseException

Forwards this call to the base class and to the buddy locker.

Overrides:

releaseNonTxnLocks in class BasicLocker

Throws:

DatabaseException

sharesLocksWith

public boolean sharesLocksWith(Locker other)

Returns whether this locker can share locks with the given locker.

Overrides:

sharesLocksWith in class Locker

getLockTimeout

public long getLockTimeout()

Returns the lock timeout of the buddy locker, since this locker has no independent timeout.

Overrides:

getLockTimeout in class Locker

getTxnTimeout

public long getTxnTimeout()

Returns the transaction timeout of the buddy locker, since this locker has no independent timeout.

Overrides:

getTxnTimeout in class Locker

setLockTimeout

public void setLockTimeout(long timeout)

Sets the lock timeout of the buddy locker, since this locker has no independent timeout.

Overrides:

setLockTimeout in class Locker

Parameters:

timeout - The timeout value for the transaction lifetime, in milliseconds. A value of 0 disables timeouts for the transaction.

setTxnTimeout

public void setTxnTimeout(long timeout)

Sets the transaction timeout of the buddy locker, since this locker has no independent timeout.

Overrides:

setTxnTimeout in class Locker

Parameters:

timeout - The timeout value for the transaction lifetime, in microseconds. A value of 0 disables timeouts for the transaction.

isTimedOut

public boolean isTimedOut()

Returns whether the buddy locker is timed out, since this locker has no independent timeout.

Overrides:

isTimedOut in class Locker

getTxnStartMillis

public long getTxnStartMillis()

Returns the buddy locker's start time, since this locker has no independent timeout.

setOnlyAbortable

public void setOnlyAbortable(OperationFailureException cause)

Forwards to the buddy locker, since the buddy may be transactional.

Overrides:

setOnlyAbortable in class Locker

checkPreempted

public void checkPreempted(Locker allowPreemptedLocker)
                    throws OperationFailureException

Forwards to the parent buddy locker, so the buddy can check itself and all of its child buddies.

Overrides:

checkPreempted in class Locker

Parameters:

allowPreemptedLocker - is a locker that is being closed as the result of a cursor move operation. If the operation is successful then allowPreemptedLocker will be closed, and the fact that a lock has been stolen from allowPreemptedLocker can be ignored.

Throws:

OperationFailureException

isReplicated

public boolean isReplicated()

Consider this locker replicated if its buddy (Txn) is replicated.

Overrides:

isReplicated in class Locker

isLocalWrite

public boolean isLocalWrite()

Consider this locker local-write if its buddy is local-write.

Overrides:

isLocalWrite in class Locker