Package org.graylog2.cluster.lock

Class MongoLockService

java.lang.Object

org.graylog2.cluster.lock.MongoLockService

All Implemented Interfaces:

LockService

@Singleton
public class MongoLockService
extends Object
implements LockService

Lock service implementation using MongoDB to maintain locks. Unless a lock is kept alive by periodically re-requesting the same lock, it will eventually expire. Lock expiry is handled by MongoDB internally. We set lock expiry to 60 seconds, but in practice it may take up to ~2 minutes until a lock really expires.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	COLLECTION_NAME
static final Duration	MIN_LOCK_TTL

Constructor Summary

Constructors

Constructor	Description
MongoLockService(NodeId nodeId, MongoConnection mongoConnection, Duration lockTTL)

Method Summary

Modifier and Type	Method	Description
Optional<Lock>	extendLock(Lock lock)	Extend the expiry time of an existing lock.
Optional<Lock>	lock(String resource)	Request a lock.
Optional<Lock>	lock(String resource, String lockContext)	Request a lock.
Optional<Lock>	unlock(String resource, String lockContext)	Unlock an existing lock.
Optional<Lock>	unlock(Lock lock)	Unlock an existing lock.

Methods inherited from class java.lang.Object

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

Field Details

COLLECTION_NAME

public static final String COLLECTION_NAME

See Also:

• Constant Field Values

MIN_LOCK_TTL

public static final Duration MIN_LOCK_TTL

Constructor Details

MongoLockService

@Inject
public MongoLockService(NodeId nodeId,
 MongoConnection mongoConnection,
 @Named("lock_service_lock_ttl")
 Duration lockTTL)

Method Details

lock

public Optional<Lock> lock(@Nonnull
 String resource,
 @Nullable
 String lockContext)

Description copied from interface: LockService

Request a lock. If a lock already exists, the lock expiry time will be extended.

Specified by:

lock in interface LockService

Parameters:

resource - Unique identifier for the resource that should be guarded by this lock.

lockContext - an identifier that will be appended to the callers' node id. This will create the lock owner string. A context can be used for resources that should only allow a single lock to be acquired, even from the same node. If the lockContext is null, only the nodeId will be used.

Returns:

A Lock object, if a lock was obtained. An empty Optional, if no lock could be acquired.

lock

public Optional<Lock> lock(@Nonnull
 String resource)

Description copied from interface: LockService

Request a lock. If a lock already exists, the lock expiry time will be extended.

Specified by:

lock in interface LockService

Parameters:

resource - Unique identifier for the resource that should be guarded by this lock.

Returns:

A Lock object, if a lock was obtained. An empty Optional, if no lock could be acquired.

extendLock

public Optional<Lock> extendLock(@Nonnull
 Lock lock)

Description copied from interface: LockService

Extend the expiry time of an existing lock.

Specified by:

extendLock in interface LockService

Parameters:

lock - the lock that should be extended.

Returns:

A Lock object, if the lock could be extended. An empty Optional, if no lock extension could be acquired.

unlock

public Optional<Lock> unlock(@Nonnull
 String resource,
 @Nullable
 String lockContext)

Description copied from interface: LockService

Unlock an existing lock.

Specified by:

unlock in interface LockService

Parameters:

resource - Unique identifier for the resource that was guarded by this lock.

lockContext - the lockContext that was used to guard this lock.

Returns:

A Lock object, if the lock could be unlocked. An empty Optional, if no lock was found.

unlock

public Optional<Lock> unlock(@Nonnull
 Lock lock)

Description copied from interface: LockService

Unlock an existing lock.

Specified by:

unlock in interface LockService

Parameters:

lock - The lock to unlock.

Returns:

A Lock object, if the lock could be unlocked. An empty Optional, if no lock was found.