alluxio.master.metastore.rocks

Class RocksUtils

java.lang.Object

alluxio.master.metastore.rocks.RocksUtils

public final class RocksUtils
extends Object

Convenience methods for working with RocksDB.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	RocksUtils.RocksIteratorParser<T> Used to parse current RocksIterator element.

Method Summary

Modifier and Type	Method and Description
static <T> CloseableIterator<T>	createCloseableIterator(org.rocksdb.RocksIterator rocksIterator, RocksUtils.RocksIteratorParser<T> parser, java.util.function.Supplier<Void> abortCheck, RocksSharedLockHandle rocksDbSharedLock) Used to wrap an CloseableIterator over RocksIterator.
static long	readLong(byte[] bytes, int start)
static byte[]	toByteArray(long long1, long long2)
static byte[]	toByteArray(long n, String str)

Methods inherited from class java.lang.Object

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

Method Detail

toByteArray

public static byte[] toByteArray(long long1,
                                 long long2)

Parameters:

long1 - a long value

long2 - a long value

Returns:

a byte array formed by writing the two long values as bytes

toByteArray

public static byte[] toByteArray(long n,
                                 String str)

Parameters:

n - a long value

str - a string value

Returns:

a byte array formed by writing the bytes of n followed by the bytes of str

readLong

public static long readLong(byte[] bytes,
                            int start)

Parameters:

bytes - an array of bytes

start - the place in the array to read the long from

Returns:

the long

createCloseableIterator

public static <T> CloseableIterator<T> createCloseableIterator(org.rocksdb.RocksIterator rocksIterator,
                                                               RocksUtils.RocksIteratorParser<T> parser,
                                                               java.util.function.Supplier<Void> abortCheck,
                                                               RocksSharedLockHandle rocksDbSharedLock)

Used to wrap an CloseableIterator over RocksIterator. It seeks given iterator to first entry before returning the iterator. The Iterator is associated with a shared lock to the RocksStore. The lock should be acquired by the caller (See java doc on RocksStore.checkAndAcquireSharedLock()) for how. And the lock is held throughout the lifecycle of this iterator until it is closed either on completion or on exception. This shared lock guarantees thread safety when accessing the RocksDB. In other words, when this shared lock is held, the underlying RocksDB will not be stopped/restarted. The abortCheck defines a way to voluntarily abort the iteration. This typically happens when the underlying RocksDB will be closed/restart/checkpointed, where all accesses should be stopped. With the thread safety baked into hasNext() and next(), users of this Iterator do not need to worry about safety and can use this Iterator normally. See examples in how this iterator is used in RocksBlockMetaStore and RocksInodeStore.

Type Parameters:

T - iterator value type

Parameters:

rocksIterator - the rocks iterator

parser - parser to produce iterated values from rocks key-value

abortCheck - if true, abort the iteration

rocksDbSharedLock - the shared lock acquired by the iterator

Returns:

wrapped iterator