org.apache.hadoop.hive.metastore

Class MaterializationsRebuildLockHandler

java.lang.Object

org.apache.hadoop.hive.metastore.MaterializationsRebuildLockHandler

public class MaterializationsRebuildLockHandler
extends Object

This is a lock handler implementation for the materializations rebuild. It is lightweight: it does not persist any information to metastore db. Its states are as follows: 1) request lock -> 2) ACQUIRED -> 4) COMMIT_READY -> 6) release lock -> 5) EXPIRED -> -> 3) NOT_ACQUIRED First, the rebuild operation will ACQUIRE the lock. If other rebuild operation for the same operation is already running, we lock status will be NOT_ACQUIRED. Before committing the rebuild, the txn handler will signal the handler that it is ready to commit the resource (move state to COMMIT_READY). We make sure the lock is still available before moving to the new state. A lock will not be able to expire when it is in COMMIT_READY state. The unlock method is always call by the txn handler, no matter whether the transaction succeeds or not, e.g., due to an Exception. From ACQUIRED, locks can be also moved to EXPIRED state when they expire. From EXPIRED, they can only be released.

Method Summary

Modifier and Type	Method and Description
long	cleanupResourceLocks(long timeout) Method that removes from the handler those locks that have expired.
static MaterializationsRebuildLockHandler	get() Get instance of MaterializationsRebuildLockHandler.
org.apache.hadoop.hive.metastore.api.LockResponse	lockResource(String dbName, String tableName, long txnId) Lock materialized view (first step for rebuild).
boolean	readyToCommitResource(String dbName, String tableName, long txnId) Moves from ACQUIRED state to COMMIT_READY.
boolean	refreshLockResource(String dbName, String tableName, long txnId) Heartbeats a certain lock and refreshes its timer.
boolean	unlockResource(String dbName, String tableName, long txnId) Releases a certain lock.

Methods inherited from class java.lang.Object

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

Method Detail

get

public static MaterializationsRebuildLockHandler get()

Get instance of MaterializationsRebuildLockHandler.

Returns:

the singleton

lockResource

public org.apache.hadoop.hive.metastore.api.LockResponse lockResource(String dbName,
                                                                      String tableName,
                                                                      long txnId)

Lock materialized view (first step for rebuild). Response contains a lock id that corresponds to the input transaction id, and whether the lock was ACQUIRED or NOT_ACQUIRED.

Parameters:

dbName - the db name of the materialization

tableName - the table name of the materialization

txnId - the transaction id for the rebuild

Returns:

the response to the lock request

readyToCommitResource

public boolean readyToCommitResource(String dbName,
                                     String tableName,
                                     long txnId)

Moves from ACQUIRED state to COMMIT_READY.

Parameters:

dbName - the db name of the materialization

tableName - the table name of the materialization

txnId - the transaction id for the rebuild

Returns:

true if the lock was still active and we could move the materialization to COMMIT_READY state, false otherwise

refreshLockResource

public boolean refreshLockResource(String dbName,
                                   String tableName,
                                   long txnId)

Heartbeats a certain lock and refreshes its timer.

Parameters:

dbName - the db name of the materialization

tableName - the table name of the materialization

txnId - the transaction id for the rebuild

Throws:

org.apache.hadoop.hive.metastore.api.MetaException

unlockResource

public boolean unlockResource(String dbName,
                              String tableName,
                              long txnId)

Releases a certain lock.

Parameters:

dbName - the db name of the materialization

tableName - the table name of the materialization

txnId - the transaction id for the rebuild

Returns:

true if the lock could be released properly, false otherwise

Throws:

org.apache.hadoop.hive.metastore.api.MetaException

cleanupResourceLocks

public long cleanupResourceLocks(long timeout)

Method that removes from the handler those locks that have expired.

Parameters:

timeout - time after which we consider the locks to have expired

Throws:

org.apache.hadoop.hive.metastore.api.MetaException