ObserverMaster (Apache ZooKeeper

java.lang.Object
- org.apache.zookeeper.server.quorum.LearnerMaster
- - org.apache.zookeeper.server.quorum.ObserverMaster

All Implemented Interfaces:

Runnable
```
public class ObserverMaster
extends LearnerMaster
implements Runnable
```
Used by Followers to host Observers. This reduces the network load on the Leader process by pushing the responsibility for keeping Observers in sync off the leading peer. It is expected that Observers will continue to perform the initial vetting of clients and requests. Observers send the request to the follower where it is received by an ObserverMaster. The ObserverMaster forwards a copy of the request to the ensemble Leader and inserts it into its own request processor pipeline where it can be matched with the response comes back. All commits received from the Leader will be forwarded along to every Learner connected to the ObserverMaster. New Learners connecting to a Follower will receive a LearnerHandler object and be party to its syncing logic to be brought up to date. The logic is quite a bit simpler than the corresponding logic in Leader because it only hosts observers.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`addLearnerHandler(LearnerHandler learnerHandler)` start tracking a learner handler
`Iterable<Map<String,Object>>`	`getActiveObservers()`
`long`	`getAndDecrementFollowerCounter()` decrement follower count
`int`	`getCurrentTick()` the current tick
`long`	`getEpochToPropose(long sid, long lastAcceptedEpoch)` get the first zxid of the next epoch
`long`	`getLastProposed()` last proposed zxid
`String`	`getPeerInfo(long sid)`
`QuorumAuthServer`	`getQuorumAuthServer()`
`byte[]`	`getQuorumVerifierBytes()` identifier of current quorum verifier for new leader
`long`	`getQuorumVerifierVersion()` version of current quorum verifier
`int`	`getTickOfInitialAckDeadline()` next deadline tick marking observer sync (steady state)
`int`	`getTickOfNextAckDeadline()` deadline tick marking observer sync (initial)
`ZKDatabase`	`getZKDatabase()` ZKDatabase
`void`	`processAck(long sid, long zxid, SocketAddress localSocketAddress)` handle ack packet
`void`	`registerLearnerHandlerBean(LearnerHandler learnerHandler, Socket socket)` registers the handler's bean
`void`	`removeLearnerHandler(LearnerHandler learnerHandler)` stop tracking a learner handler
`void`	`resetObserverConnectionStats()`
`void`	`revalidateSession(QuorumPacket qp, LearnerHandler learnerHandler)` handle revalidate packet
`void`	`run()`
`void`	`start()`
`long`	`startForwarding(LearnerHandler learnerHandler, long lastSeenZxid)` begin forwarding packets to learner handler
`void`	`stop()`
`void`	`submitLearnerRequest(Request si)` proxy request from learner to server
`int`	`syncTimeout()` time allowed for sync response
`void`	`touch(long sess, int to)` mark session as alive
`void`	`unregisterLearnerHandlerBean(LearnerHandler learnerHandler)` unregisters the handler's bean
`void`	`waitForEpochAck(long sid, StateSummary ss)` wait for the leader of the new epoch to be confirmed by followers
`void`	`waitForNewLeaderAck(long sid, long zxid)` wait for new leader to settle
`void`	`waitForStartup()` wait for server to start

Methods inherited from class org.apache.zookeeper.server.quorum.LearnerMaster
getLearnerDiffSyncThrottler, getLearnerSnapSyncThrottler, getMaxConcurrentDiffSyncs, getMaxConcurrentSnapSyncs, setMaxConcurrentDiffSyncs, setMaxConcurrentSnapSyncs

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

- Method Detail
  - addLearnerHandler
```
public void addLearnerHandler(LearnerHandler learnerHandler)
```
    Description copied from class: LearnerMaster
    
    start tracking a learner handler
    
    Parameters:
    
    learnerHandler - to track
  - removeLearnerHandler
```
public void removeLearnerHandler(LearnerHandler learnerHandler)
```
    Description copied from class: LearnerMaster
    
    stop tracking a learner handler
    
    Parameters:
    
    learnerHandler - to drop
  - syncTimeout
```
public int syncTimeout()
```
    Description copied from class: LearnerMaster
    
    time allowed for sync response
    
    Returns:
    
    time allowed for sync response
  - getTickOfNextAckDeadline
```
public int getTickOfNextAckDeadline()
```
    Description copied from class: LearnerMaster
    
    deadline tick marking observer sync (initial)
    
    Returns:
    
    deadline tick marking observer sync (initial)
  - getTickOfInitialAckDeadline
```
public int getTickOfInitialAckDeadline()
```
    Description copied from class: LearnerMaster
    
    next deadline tick marking observer sync (steady state)
    
    Returns:
    
    next deadline tick marking observer sync (steady state)
  - getAndDecrementFollowerCounter
```
public long getAndDecrementFollowerCounter()
```
    Description copied from class: LearnerMaster
    
    decrement follower count
    
    Returns:
    
    previous follower count
  - waitForEpochAck
```
public void waitForEpochAck(long sid,
                            StateSummary ss)
                     throws IOException,
                            InterruptedException
```
    Description copied from class: LearnerMaster
    
    wait for the leader of the new epoch to be confirmed by followers
    
    Parameters:
    
    sid - learner id
    
    Throws:
    
    IOException
    
    InterruptedException
  - waitForStartup
```
public void waitForStartup()
                    throws InterruptedException
```
    Description copied from class: LearnerMaster
    
    wait for server to start
    
    Throws:
    
    InterruptedException
  - getLastProposed
```
public long getLastProposed()
```
    Description copied from class: LearnerMaster
    
    last proposed zxid
    
    Returns:
    
    last proposed zxid
  - getEpochToPropose
```
public long getEpochToPropose(long sid,
                              long lastAcceptedEpoch)
                       throws InterruptedException,
                              IOException
```
    Description copied from class: LearnerMaster
    
    get the first zxid of the next epoch
    
    Parameters:
    
    sid - learner id
    
    Returns:
    
    the first zxid of the next epoch
    
    Throws:
    
    InterruptedException
    
    IOException
  - getZKDatabase
```
public ZKDatabase getZKDatabase()
```
    Description copied from class: LearnerMaster
    
    ZKDatabase
    
    Returns:
    
    ZKDatabase
  - waitForNewLeaderAck
```
public void waitForNewLeaderAck(long sid,
                                long zxid)
                         throws InterruptedException
```
    Description copied from class: LearnerMaster
    
    wait for new leader to settle
    
    Parameters:
    
    sid - id of learner
    
    zxid - zxid at learner
    
    Throws:
    
    InterruptedException
  - getCurrentTick
```
public int getCurrentTick()
```
    Description copied from class: LearnerMaster
    
    the current tick
    
    Returns:
    
    the current tick
  - processAck
```
public void processAck(long sid,
                       long zxid,
                       SocketAddress localSocketAddress)
```
    Description copied from class: LearnerMaster
    
    handle ack packet
    
    Parameters:
    
    sid - leader id
    
    zxid - packet zxid
    
    localSocketAddress - forwarder's address
  - touch
```
public void touch(long sess,
                  int to)
```
    Description copied from class: LearnerMaster
    
    mark session as alive
    
    Parameters:
    
    sess - session id
    
    to - timeout
  - revalidateSession
```
public void revalidateSession(QuorumPacket qp,
                              LearnerHandler learnerHandler)
                       throws IOException
```
    Description copied from class: LearnerMaster
    
    handle revalidate packet
    
    Parameters:
    
    qp - session packet
    
    learnerHandler - learner
    
    Throws:
    
    IOException
  - submitLearnerRequest
```
public void submitLearnerRequest(Request si)
```
    Description copied from class: LearnerMaster
    
    proxy request from learner to server
    
    Parameters:
    
    si - request
  - startForwarding
```
public long startForwarding(LearnerHandler learnerHandler,
                            long lastSeenZxid)
```
    Description copied from class: LearnerMaster
    
    begin forwarding packets to learner handler
    
    Parameters:
    
    learnerHandler - learner
    
    lastSeenZxid - zxid of learner
    
    Returns:
    
    last zxid forwarded
  - getQuorumVerifierVersion
```
public long getQuorumVerifierVersion()
```
    Description copied from class: LearnerMaster
    
    version of current quorum verifier
    
    Returns:
    
    version of current quorum verifier
  - getPeerInfo
```
public String getPeerInfo(long sid)
```
    Parameters:
    
    sid - server id
    
    Returns:
    
    server information in the view
  - getQuorumVerifierBytes
```
public byte[] getQuorumVerifierBytes()
```
    Description copied from class: LearnerMaster
    
    identifier of current quorum verifier for new leader
    
    Returns:
    
    identifier of current quorum verifier for new leader
  - getQuorumAuthServer
```
public QuorumAuthServer getQuorumAuthServer()
```
  - start
```
public void start()
           throws IOException
```
    Throws:
    
    IOException
  - run
```
public void run()
```
    Specified by:
    
    run in interface Runnable
  - stop
```
public void stop()
```
  - getActiveObservers
```
public Iterable<Map<String,Object>> getActiveObservers()
```
  - resetObserverConnectionStats
```
public void resetObserverConnectionStats()
```
  - registerLearnerHandlerBean
```
public void registerLearnerHandlerBean(LearnerHandler learnerHandler,
                                       Socket socket)
```
    Description copied from class: LearnerMaster
    
    registers the handler's bean
    
    Parameters:
    
    learnerHandler - handler
    
    socket - connection to learner
  - unregisterLearnerHandlerBean
```
public void unregisterLearnerHandlerBean(LearnerHandler learnerHandler)
```
    Description copied from class: LearnerMaster
    
    unregisters the handler's bean
    
    Parameters:
    
    learnerHandler - handler

Class ObserverMaster

Method Summary

Methods inherited from class org.apache.zookeeper.server.quorum.LearnerMaster

Methods inherited from class java.lang.Object

Method Detail

addLearnerHandler

removeLearnerHandler

syncTimeout

getTickOfNextAckDeadline

getTickOfInitialAckDeadline

getAndDecrementFollowerCounter

waitForEpochAck

waitForStartup

getLastProposed

getEpochToPropose

getZKDatabase

waitForNewLeaderAck

getCurrentTick

processAck

touch

revalidateSession

submitLearnerRequest

startForwarding

getQuorumVerifierVersion

getPeerInfo

getQuorumVerifierBytes

getQuorumAuthServer

start

run

stop

getActiveObservers

resetObserverConnectionStats

registerLearnerHandlerBean

unregisterLearnerHandlerBean