java.lang.Object
- org.apache.zookeeper.server.quorum.QuorumCnxManager

```
public class QuorumCnxManager
extends Object
```
This class implements a connection manager for leader election using TCP. It maintains one connection for every pair of servers. The tricky part is to guarantee that there is exactly one connection for every pair of servers that are operating correctly and that can communicate over the network. If two servers try to start a connection concurrently, then the connection manager uses a very simple tie-breaking mechanism to decide which connection to drop based on the IP addressed of the two parties. For every peer, the manager maintains a queue of messages to send. If the connection to any particular peer drops, then the sender thread puts the message back on the list. As this implementation currently uses a queue implementation to maintain messages to send to another peer, we add the message to the tail of the queue, thus changing the order of messages. Although this is not a problem for the leader election, it could be a problem when consolidating peer communication. This is to be verified, though.

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`static class`	`QuorumCnxManager.InitialMessage`
`class`	`QuorumCnxManager.Listener`	Thread to listen on some ports
`static class`	`QuorumCnxManager.Message`

Field Summary

Fields
Modifier and Type	Field	Description
`QuorumCnxManager.Listener`	`listener`
`static int`	`maxBuffer`
`static long`	`PROTOCOL_VERSION_V1`
`static long`	`PROTOCOL_VERSION_V2`
`BlockingQueue<QuorumCnxManager.Message>`	`recvQueue`

Constructor Summary

Constructors
Constructor	Description
`QuorumCnxManager(QuorumPeer self, long mySid, Map<Long,QuorumPeer.QuorumServer> view, QuorumAuthServer authServer, QuorumAuthLearner authLearner, int socketTimeout, boolean listenOnAllIPs, int quorumCnxnThreadsSize, boolean quorumSaslAuthEnabled)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`addToRecvQueue(QuorumCnxManager.Message msg)`	Inserts an element in the `recvQueue`.
`void`	`connectAll()`	Try to establish a connection with each server if one doesn't exist.
`boolean`	`connectedToPeer(long peerSid)`
`long`	`getConnectionThreadCount()`	Return number of connection processing threads.
`long`	`getThreadCount()`	Return number of worker threads
`void`	`halt()`	Flag that it is time to wrap up all activities and interrupt the listener.
`void`	`initiateConnection(MultipleAddresses electionAddr, Long sid)`	First we create the socket, perform SSL handshake and authentication if needed.
`boolean`	`initiateConnectionAsync(MultipleAddresses electionAddr, Long sid)`	Server will initiate the connection request to its peer server asynchronously via separate connection thread.
`boolean`	`isReconfigEnabled()`
`QuorumCnxManager.Message`	`pollRecvQueue(long timeout, TimeUnit unit)`	Retrieves and removes a message at the head of this queue, waiting up to the specified wait time if necessary for an element to become available.
`void`	`receiveConnection(Socket sock)`	If this server receives a connection request, then it gives up on the new connection if it wins.
`void`	`receiveConnectionAsync(Socket sock)`	Server receives a connection request and handles it asynchronously via separate thread.
`void`	`softHalt()`	A soft halt simply finishes workers.
`void`	`testInitiateConnection(long sid)`	Invokes initiateConnection for testing purposes
`void`	`toSend(Long sid, ByteBuffer b)`	Processes invoke this message to queue a message to send.

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

- Field Detail
  - PROTOCOL_VERSION_V1
```
public static final long PROTOCOL_VERSION_V1
```
    See Also:
    
    Constant Field Values
  - PROTOCOL_VERSION_V2
```
public static final long PROTOCOL_VERSION_V2
```
    See Also:
    
    Constant Field Values
  - maxBuffer
```
public static final int maxBuffer
```
    See Also:
    
    Constant Field Values
  - recvQueue
```
public final BlockingQueue<QuorumCnxManager.Message> recvQueue
```
  - listener
```
public final QuorumCnxManager.Listener listener
```
- Constructor Detail
  - QuorumCnxManager
```
public QuorumCnxManager(QuorumPeer self,
                        long mySid,
                        Map<Long,QuorumPeer.QuorumServer> view,
                        QuorumAuthServer authServer,
                        QuorumAuthLearner authLearner,
                        int socketTimeout,
                        boolean listenOnAllIPs,
                        int quorumCnxnThreadsSize,
                        boolean quorumSaslAuthEnabled)
```
- Method Detail
  - testInitiateConnection
```
public void testInitiateConnection(long sid)
```
    Invokes initiateConnection for testing purposes
    
    Parameters:
    
    sid -
  - initiateConnection
```
public void initiateConnection(MultipleAddresses electionAddr,
                               Long sid)
```
    First we create the socket, perform SSL handshake and authentication if needed. Then we perform the initiation protocol. If this server has initiated the connection, then it gives up on the connection if it loses challenge. Otherwise, it keeps the connection.
  - initiateConnectionAsync
```
public boolean initiateConnectionAsync(MultipleAddresses electionAddr,
                                       Long sid)
```
    Server will initiate the connection request to its peer server asynchronously via separate connection thread.
  - receiveConnection
```
public void receiveConnection(Socket sock)
```
    If this server receives a connection request, then it gives up on the new connection if it wins. Notice that it checks whether it has a connection to this server already or not. If it does, then it sends the smallest possible long value to lose the challenge.
  - receiveConnectionAsync
```
public void receiveConnectionAsync(Socket sock)
```
    Server receives a connection request and handles it asynchronously via separate thread.
  - toSend
```
public void toSend(Long sid,
                   ByteBuffer b)
```
    Processes invoke this message to queue a message to send. Currently, only leader election uses it.
  - connectAll
```
public void connectAll()
```
    Try to establish a connection with each server if one doesn't exist.
  - halt
```
public void halt()
```
    Flag that it is time to wrap up all activities and interrupt the listener.
  - softHalt
```
public void softHalt()
```
    A soft halt simply finishes workers.
  - getThreadCount
```
public long getThreadCount()
```
    Return number of worker threads
  - getConnectionThreadCount
```
public long getConnectionThreadCount()
```
    Return number of connection processing threads.
  - addToRecvQueue
```
public void addToRecvQueue(QuorumCnxManager.Message msg)
```
    Inserts an element in the recvQueue. If the Queue is full, this methods removes an element from the head of the Queue and then inserts the element at the tail of the queue.
    
    Parameters:
    
    msg - Reference to the message to be inserted in the queue
  - pollRecvQueue
```
public QuorumCnxManager.Message pollRecvQueue(long timeout,
                                              TimeUnit unit)
                                       throws InterruptedException
```
    Retrieves and removes a message at the head of this queue, waiting up to the specified wait time if necessary for an element to become available. BlockingQueue.poll(long, java.util.concurrent.TimeUnit)
    
    Throws:
    
    InterruptedException
  - connectedToPeer
```
public boolean connectedToPeer(long peerSid)
```
  - isReconfigEnabled
```
public boolean isReconfigEnabled()
```

Class QuorumCnxManager

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

PROTOCOL_VERSION_V1

PROTOCOL_VERSION_V2

maxBuffer

recvQueue

listener

Constructor Detail

QuorumCnxManager

Method Detail

testInitiateConnection

initiateConnection

initiateConnectionAsync

receiveConnection

receiveConnectionAsync

toSend

connectAll

halt

softHalt

getThreadCount

getConnectionThreadCount

addToRecvQueue

pollRecvQueue

connectedToPeer

isReconfigEnabled