org.apache.hadoop.hive.metastore.txn

Interface TxnStore.MutexAPI

All Known Implementing Classes:

TxnHandler, TxnStoreMutex

Enclosing interface:

TxnStore

public static interface TxnStore.MutexAPI

This is primarily designed to provide coarse-grained mutex support to operations running inside the Metastore (of which there could be several instances). The initial goal is to ensure that various sub-processes of the Compactor don't step on each other. In RDMBS world each LockHandle uses a java.sql.Connection so use it sparingly.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	TxnStore.MutexAPI.LockHandle

Method Summary

Modifier and Type	Method and Description
TxnStore.MutexAPI.LockHandle	acquireLock(String key) The key is name of the lock.
void	acquireLock(String key, TxnStore.MutexAPI.LockHandle handle) Same as acquireLock(String) but takes an already existing handle as input.

Method Detail

acquireLock

TxnStore.MutexAPI.LockHandle acquireLock(String key)
                                  throws MetaException

The key is name of the lock. Will acquire an exclusive lock or block. It returns a handle which must be used to release the lock. Each invocation returns a new handle.

Throws:

MetaException

acquireLock

void acquireLock(String key,
                 TxnStore.MutexAPI.LockHandle handle)
          throws MetaException

Same as acquireLock(String) but takes an already existing handle as input. This will associate the lock on key with the same handle. All locks associated with the same handle will be released together.

Parameters:

handle - not NULL

Throws:

MetaException