Package org.apache.bookkeeper.meta

Class LongZkLedgerIdGenerator

java.lang.Object

org.apache.bookkeeper.meta.LongZkLedgerIdGenerator

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, LedgerIdGenerator

public class LongZkLedgerIdGenerator
extends java.lang.Object
implements LedgerIdGenerator

ZooKeeper based ledger id generator class, which using EPHEMERAL_SEQUENTIAL with (ledgerIdGenPath)/HOB-[high-32-bits]/ID- prefix to generate ledger id. Note zookeeper sequential counter has a format of %10d -- that is 10 digits with 0 (zero) padding, i.e. "<path>0000000001", so ledger id space would be fundamentally limited to 9 billion. In practice, the id generated by zookeeper is only 31 bits (signed 32-bit integer), so the limit is much lower than 9 billion.

In order to support the full range of the long ledgerId, once ledgerIds reach Integer.MAX_INT, a new system is employed. The 32 most significant bits of the ledger ID are taken and turned into a directory prefixed with HOB- under (ledgerIdGenPath)

Under this HOB- directory, zookeeper is used to continue generating EPHEMERAL_SEQUENTIAL ids which constitute the lower 32-bits of the ledgerId (sign bit is always 0). Once the HOB- directory runs out of available ids, the process is repeated. The higher bits are incremented, a new HOB- directory is created, and zookeeper generates sequential ids underneath it.

The reason for treating ids which are less than Integer.MAX_INT differently is to maintain backwards compatibility. This is a drop-in replacement for ZkLedgerIdGenerator.

Constructor Summary

Constructors

Constructor	Description
LongZkLedgerIdGenerator(org.apache.zookeeper.ZooKeeper zk, java.lang.String ledgersPath, java.lang.String idGenZnodeName, ZkLedgerIdGenerator shortIdGen, java.util.List<org.apache.zookeeper.data.ACL> zkAcls)

Method Summary

Modifier and Type	Method	Description
void	close()
void	generateLedgerId(BookkeeperInternalCallbacks.GenericCallback<java.lang.Long> cb)	Generate a global unique ledger id.
void	invalidateLedgerIdGenPathStatus()
boolean	ledgerIdGenPathPresent(org.apache.zookeeper.ZooKeeper zk)	Checks the existence of the long ledger id gen path.

Methods inherited from class java.lang.Object

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

Constructor Detail

LongZkLedgerIdGenerator

public LongZkLedgerIdGenerator(org.apache.zookeeper.ZooKeeper zk,
                               java.lang.String ledgersPath,
                               java.lang.String idGenZnodeName,
                               ZkLedgerIdGenerator shortIdGen,
                               java.util.List<org.apache.zookeeper.data.ACL> zkAcls)

Method Detail

invalidateLedgerIdGenPathStatus

public void invalidateLedgerIdGenPathStatus()

ledgerIdGenPathPresent

public boolean ledgerIdGenPathPresent(org.apache.zookeeper.ZooKeeper zk)
                               throws org.apache.zookeeper.KeeperException,
                                      java.lang.InterruptedException

Checks the existence of the long ledger id gen path. Existence indicates we have switched from the legacy algorithm to the new method of generating 63-bit ids. If the existence is UNKNOWN, it looks in zk to find out. If it previously checked in zk, it returns that value. This value changes when we run out of ids < Integer.MAX_VALUE, and try to create the long ledger id gen path.

Parameters:

zk -

Returns:

Does the long ledger id gen path exist?

Throws:

org.apache.zookeeper.KeeperException

java.lang.InterruptedException

See Also:

createLongLedgerIdPathAndGenerateLongLedgerId(org.apache.bookkeeper.proto.BookkeeperInternalCallbacks.GenericCallback<java.lang.Long>,java.lang.String)

generateLedgerId

public void generateLedgerId(BookkeeperInternalCallbacks.GenericCallback<java.lang.Long> cb)

Description copied from interface: LedgerIdGenerator

Generate a global unique ledger id.

Specified by:

generateLedgerId in interface LedgerIdGenerator

Parameters:

cb - Callback when a new ledger id is generated, return code:

• BKException.Code.OK if success
• BKException.Code.ZKException when can't generate new ledger id

close

public void close()
           throws java.io.IOException

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface java.io.Closeable

Throws:

java.io.IOException