com.tailf.ha

Class Ha

Object

com.tailf.ha.Ha

public class Ha
extends Object

Main class for the HA cluster management. The HA functionality makes it possible to replicate the configuration data on several nodes in a cluster. The details on usage of the HA api is described in the UserGuide.

Constructor Summary

Constructors

Constructor and Description
Ha(Socket socket, String token) Constructor for management of an HA Cluster node.

Method Summary

Modifier and Type	Method and Description
void	beMaster(ConfValue myNodeId) Instruct an HA node to be master and also give the node a name.
void	beNone() Instruct a node to resume the initial state, i.e.
void	beRelay() Instruct a slave node to be a relay for other slaves.
void	beSlave(ConfValue myNodeId, ConfHaNode master, boolean waitForReply) Instruct an HA node to be a slave to a named master.
void	slaveDead(ConfValue nodeId) This function must be used by the application to inform the HA subsystem that another node which is possibly connected to the server is dead.
HaStatus	status() Query an HA node for its status.

Methods inherited from class Object

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

Constructor Detail

Ha

public Ha(Socket socket,
          String token)
   throws IOException,
          HaException

Constructor for management of an HA Cluster node. This constructor implicitly connects an HA socket which can be used to control a ConfD/NCS HA node. The token is a secret string that must be shared by all participants in the cluster. There can only be one HA socket towards the server, which implies only on HA instance. If a new HA instance is created the previous connection is closed and the cluster node is reset with the new token value.

Since the ConfD/NCS daemon expects initialization within 5 seconds after a new socket is established, this constructor should be called immediately for a new socket. For instance:

 // int port = Conf.PORT for ConfD or Conf.NCS_PORT for NCS
 Ha ha = new Ha(new Socket("localhost", port), "xyz");
 

If encrypted communication towards ConfD/NCS is desired, an environment variable "CONFD_IPC_ACCESS_FILE" or "NCS_IPC_ACCESS_FILE" need to be set. This variable is expected to point to a file containing a secret salt. Example:

 export CONFD_IPC_ACCESS_FILE=./secret_file.txt
 

An alternative to the environment variable is to set a java system property with the same name pointing to the file.

Note, if this constructor fails the socket must be closed and a new socket created before the call is re-attempted.

Parameters:

socket - Ha control socket

token - cluster common shared secret

Throws:

IOException

HaException

Method Detail

beMaster

public void beMaster(ConfValue myNodeId)
              throws IOException,
                     HaException

Instruct an HA node to be master and also give the node a name.

Parameters:

myNodeId - ConfValue naming the ha node

Throws:

IOException

HaException

beSlave

public void beSlave(ConfValue myNodeId,
                    ConfHaNode master,
                    boolean waitForReply)
             throws IOException,
                    HaException

Instruct an HA node to be a slave to a named master. The waitreply is a boolean. If true, the function is synchronous and it will hang until the node has initialized its CDB database. This may mean that the CDB database is copied in its entirety from the master. If false, we do not wait for the reply, but it is possible to use a notifications socket and get notified asynchronously via an HA_INFO_BESLAVE_RESULT notification. In both cases, it is also possible to use a notifications socket and get notified asynchronously when CDB at the slave is initialized.

Parameters:

myNodeId - ConfValue naming the ha node

master - Master ConfHaNode

waitForReply - boolean, set true if call should block until response

Throws:

IOException

HaException

beNone

public void beNone()
            throws IOException,
                   HaException

Instruct a node to resume the initial state, i.e. neither master nor slave.

Throws:

IOException

HaException

beRelay

public void beRelay()
             throws IOException,
                    HaException

Instruct a slave node to be a relay for other slaves.

Throws:

IOException

HaException

status

public HaStatus status()
                throws IOException,
                       HaException

Query an HA node for its status. If successful, the function returns an HaStatus object.

Returns:

HaStatus enum indicating the status of the node

Throws:

IOException

HaException

slaveDead

public void slaveDead(ConfValue nodeId)
               throws IOException,
                      HaException

This function must be used by the application to inform the HA subsystem that another node which is possibly connected to the server is dead.

Parameters:

nodeId - ConfValue naming the cluster node

Throws:

IOException

HaException