RecoverableZooKeeper (Apache HBase 1.4.11 API)

java.lang.Object
- org.apache.hadoop.hbase.zookeeper.RecoverableZooKeeper

```
@InterfaceAudience.Private
public class RecoverableZooKeeper
extends Object
```
A zookeeper that can handle 'recoverable' errors. To handle recoverable errors, developers need to realize that there are two classes of requests: idempotent and non-idempotent requests. Read requests and unconditional sets and deletes are examples of idempotent requests, they can be reissued with the same results. (Although, the delete may throw a NoNodeException on reissue its effect on the ZooKeeper state is the same.) Non-idempotent requests need special handling, application and library writers need to keep in mind that they may need to encode information in the data or name of znodes to detect retries. A simple example is a create that uses a sequence flag. If a process issues a create("/x-", ..., SEQUENCE) and gets a connection loss exception, that process will reissue another create("/x-", ..., SEQUENCE) and get back x-111. When the process does a getChildren("/"), it sees x-1,x-30,x-109,x-110,x-111, now it could be that x-109 was the result of the previous create, so the process actually owns both x-109 and x-111. An easy way around this is to use "x-process id-" when doing the create. If the process is using an id of 352, before reissuing the create it will do a getChildren("/") and see "x-222-1", "x-542-30", "x-352-109", x-333-110". The process will know that the original create succeeded an the znode it created is "x-352-109".

See Also:
"http://wiki.apache.org/hadoop/ZooKeeper/ErrorHandling"

Constructor Summary

Constructors
Constructor and Description
`RecoverableZooKeeper(String quorumServers, int sessionTimeout, org.apache.zookeeper.Watcher watcher, int maxRetries, int retryIntervalMillis, int maxSleepTime)`
`RecoverableZooKeeper(String quorumServers, int sessionTimeout, org.apache.zookeeper.Watcher watcher, int maxRetries, int retryIntervalMillis, int maxSleepTime, String identifier)`

Method Summary

Methods
Modifier and Type	Method and Description
`protected org.apache.zookeeper.ZooKeeper`	`checkZk()` Try to create a Zookeeper connection.
`void`	`close()`
`String`	`create(String path, byte[] data, List<org.apache.zookeeper.data.ACL> acl, org.apache.zookeeper.CreateMode createMode)` NONSEQUENTIAL create is idempotent operation.
`void`	`delete(String path, int version)` delete is an idempotent operation.
`org.apache.zookeeper.data.Stat`	`exists(String path, boolean watch)` exists is an idempotent operation.
`org.apache.zookeeper.data.Stat`	`exists(String path, org.apache.zookeeper.Watcher watcher)` exists is an idempotent operation.
`List<org.apache.zookeeper.data.ACL>`	`getAcl(String path, org.apache.zookeeper.data.Stat stat)` getAcl is an idempotent operation.
`List<String>`	`getChildren(String path, boolean watch)` getChildren is an idempotent operation.
`List<String>`	`getChildren(String path, org.apache.zookeeper.Watcher watcher)` getChildren is an idempotent operation.
`byte[]`	`getData(String path, boolean watch, org.apache.zookeeper.data.Stat stat)` getData is an idemnpotent operation.
`byte[]`	`getData(String path, org.apache.zookeeper.Watcher watcher, org.apache.zookeeper.data.Stat stat)` getData is an idempotent operation.
`String`	`getIdentifier()`
`long`	`getSessionId()`
`byte[]`	`getSessionPasswd()`
`org.apache.zookeeper.ZooKeeper.States`	`getState()`
`org.apache.zookeeper.ZooKeeper`	`getZooKeeper()`
`List<org.apache.zookeeper.OpResult>`	`multi(Iterable<org.apache.zookeeper.Op> ops)` Run multiple operations in a transactional manner.
`void`	`reconnectAfterExpiration()`
`byte[]`	`removeMetaData(byte[] data)`
`org.apache.zookeeper.data.Stat`	`setAcl(String path, List<org.apache.zookeeper.data.ACL> acls, int version)` setAcl is an idempotent operation.
`org.apache.zookeeper.data.Stat`	`setData(String path, byte[] data, int version)` setData is NOT an idempotent operation.
`void`	`sync(String path, org.apache.zookeeper.AsyncCallback.VoidCallback cb, Object ctx)`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RecoverableZooKeeper

public RecoverableZooKeeper(String quorumServers,
                    int sessionTimeout,
                    org.apache.zookeeper.Watcher watcher,
                    int maxRetries,
                    int retryIntervalMillis,
                    int maxSleepTime)
                     throws IOException

Throws:: IOException

RecoverableZooKeeper

public RecoverableZooKeeper(String quorumServers,
                    int sessionTimeout,
                    org.apache.zookeeper.Watcher watcher,
                    int maxRetries,
                    int retryIntervalMillis,
                    int maxSleepTime,
                    String identifier)
                     throws IOException

Throws:: IOException

Method Detail

checkZk
```
protected org.apache.zookeeper.ZooKeeper checkZk()
                                          throws org.apache.zookeeper.KeeperException
```
Try to create a Zookeeper connection. Turns any exception encountered into a KeeperException.OperationTimeoutException so it can retried.

Returns:
The created Zookeeper connection object

Throws:

org.apache.zookeeper.KeeperException

reconnectAfterExpiration

public void reconnectAfterExpiration()
                              throws IOException,
                                     org.apache.zookeeper.KeeperException,
                                     InterruptedException

Throws:: IOException; org.apache.zookeeper.KeeperException; InterruptedException

delete
```
public void delete(String path,
          int version)
            throws InterruptedException,
                   org.apache.zookeeper.KeeperException
```
delete is an idempotent operation. Retry before throwing exception. This function will not throw NoNodeException if the path does not exist.

Throws:

InterruptedException

org.apache.zookeeper.KeeperException

exists

public org.apache.zookeeper.data.Stat exists(String path,
                                    org.apache.zookeeper.Watcher watcher)
                                      throws org.apache.zookeeper.KeeperException,
                                             InterruptedException

exists is an idempotent operation. Retry before throwing exception

Returns:: A Stat instance
Throws:: org.apache.zookeeper.KeeperException; InterruptedException

exists

public org.apache.zookeeper.data.Stat exists(String path,
                                    boolean watch)
                                      throws org.apache.zookeeper.KeeperException,
                                             InterruptedException

exists is an idempotent operation. Retry before throwing exception

Returns:: A Stat instance
Throws:: org.apache.zookeeper.KeeperException; InterruptedException

getChildren

public List<String> getChildren(String path,
                       org.apache.zookeeper.Watcher watcher)
                         throws org.apache.zookeeper.KeeperException,
                                InterruptedException

getChildren is an idempotent operation. Retry before throwing exception

Returns:: List of children znodes
Throws:: org.apache.zookeeper.KeeperException; InterruptedException

getChildren

public List<String> getChildren(String path,
                       boolean watch)
                         throws org.apache.zookeeper.KeeperException,
                                InterruptedException

getChildren is an idempotent operation. Retry before throwing exception

Returns:: List of children znodes
Throws:: org.apache.zookeeper.KeeperException; InterruptedException

getData

public byte[] getData(String path,
             org.apache.zookeeper.Watcher watcher,
             org.apache.zookeeper.data.Stat stat)
               throws org.apache.zookeeper.KeeperException,
                      InterruptedException

getData is an idempotent operation. Retry before throwing exception

Returns:: Data
Throws:: org.apache.zookeeper.KeeperException; InterruptedException

getData

public byte[] getData(String path,
             boolean watch,
             org.apache.zookeeper.data.Stat stat)
               throws org.apache.zookeeper.KeeperException,
                      InterruptedException

getData is an idemnpotent operation. Retry before throwing exception

Returns:: Data
Throws:: org.apache.zookeeper.KeeperException; InterruptedException

setData

public org.apache.zookeeper.data.Stat setData(String path,
                                     byte[] data,
                                     int version)
                                       throws org.apache.zookeeper.KeeperException,
                                              InterruptedException

setData is NOT an idempotent operation. Retry may cause BadVersion Exception Adding an identifier field into the data to check whether badversion is caused by the result of previous correctly setData

Returns:: Stat instance
Throws:: org.apache.zookeeper.KeeperException; InterruptedException

getAcl

public List<org.apache.zookeeper.data.ACL> getAcl(String path,
                                         org.apache.zookeeper.data.Stat stat)
                                           throws org.apache.zookeeper.KeeperException,
                                                  InterruptedException

getAcl is an idempotent operation. Retry before throwing exception

Returns:: list of ACLs
Throws:: org.apache.zookeeper.KeeperException; InterruptedException

setAcl

public org.apache.zookeeper.data.Stat setAcl(String path,
                                    List<org.apache.zookeeper.data.ACL> acls,
                                    int version)
                                      throws org.apache.zookeeper.KeeperException,
                                             InterruptedException

setAcl is an idempotent operation. Retry before throwing exception

Returns:: list of ACLs
Throws:: org.apache.zookeeper.KeeperException; InterruptedException

create
```
public String create(String path,
            byte[] data,
            List<org.apache.zookeeper.data.ACL> acl,
            org.apache.zookeeper.CreateMode createMode)
              throws org.apache.zookeeper.KeeperException,
                     InterruptedException
```
NONSEQUENTIAL create is idempotent operation. Retry before throwing exceptions. But this function will not throw the NodeExist exception back to the application.

But SEQUENTIAL is NOT idempotent operation. It is necessary to add identifier to the path to verify, whether the previous one is successful or not.

Returns:
Path

Throws:

org.apache.zookeeper.KeeperException

InterruptedException

multi

public List<org.apache.zookeeper.OpResult> multi(Iterable<org.apache.zookeeper.Op> ops)
                                          throws org.apache.zookeeper.KeeperException,
                                                 InterruptedException

Run multiple operations in a transactional manner. Retry before throwing exception

Throws:: org.apache.zookeeper.KeeperException; InterruptedException

removeMetaData

public byte[] removeMetaData(byte[] data)

getSessionId
```
public long getSessionId()
```

close

public void close()
           throws InterruptedException

Throws:: InterruptedException

getState

public org.apache.zookeeper.ZooKeeper.States getState()

getZooKeeper

public org.apache.zookeeper.ZooKeeper getZooKeeper()

getSessionPasswd
```
public byte[] getSessionPasswd()
```

sync

public void sync(String path,
        org.apache.zookeeper.AsyncCallback.VoidCallback cb,
        Object ctx)
          throws org.apache.zookeeper.KeeperException

Throws:: org.apache.zookeeper.KeeperException

getIdentifier
```
public String getIdentifier()
```

Class RecoverableZooKeeper

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

RecoverableZooKeeper

RecoverableZooKeeper

Method Detail

checkZk

reconnectAfterExpiration

delete

exists

exists

getChildren

getChildren

getData

getData

setData

getAcl

setAcl

create

multi

removeMetaData

getSessionId

close

getState

getZooKeeper

getSessionPasswd

sync

getIdentifier