Package org.kiwiproject.curator.leader

Class ManagedLeaderLatchCreator

java.lang.Object

org.kiwiproject.curator.leader.ManagedLeaderLatchCreator

public class ManagedLeaderLatchCreator
extends Object

Entry point to initialize ManagedLeaderLatch, which wraps an Apache Curator LeaderLatch and allows for easy determination whether a JVM process is the leader in a group of JVMs connected to a ZooKeeper cluster.

The ManagedLeaderLatch created by this class will be started immediately, but is a Dropwizard Managed so that it will be stopped when the Dropwizard service shuts down.

In addition, by default a ManagedLeaderLatchHealthCheck is registered with Dropwizard. Two REST resources are registered, GotLeaderLatchResource and LeaderResource.

Method Summary

Modifier and Type	Method	Description
ManagedLeaderLatchCreator	addLeaderLatchListener(org.apache.curator.framework.recipes.leader.LeaderLatchListener listener)	Adds the specified LeaderLatchListener.
static ManagedLeaderLatchCreator	from(org.apache.curator.framework.CuratorFramework client, io.dropwizard.setup.Environment environment, ServiceDescriptor serviceDescriptor, org.apache.curator.framework.recipes.leader.LeaderLatchListener... listeners)	Static factory method to create a ManagedLeaderLatchCreator.
Optional<ManagedLeaderLatchHealthCheck>	getHealthCheck()	Returns the health check (if registered) after start() has been called.
ManagedLeaderLatch	getLeaderLatch()	Returns the ManagedLeaderLatch created after start() has been called.
List<org.apache.curator.framework.recipes.leader.LeaderLatchListener>	getListeners()	Returns a list containing all registered LeaderLatchListeners after start() has been called.
boolean	isLeaderLatchStarted()	Has this instance created and started a ManagedLeaderLatch?
ManagedLeaderLatchCreator	start()	Starts the leader latch, performing the following actions: Creates a new ManagedLeaderLatch, starts it, and tells the Dropwizard lifecycle to manage (stop) it Creates and registers a ManagedLeaderLatchHealthCheck unless explicitly disabled via withoutHealthCheck() Creates and registers the JAX-RS REST endpoints unless explicitly disabled via withoutResources()
static ManagedLeaderLatchCreator	start(org.apache.curator.framework.CuratorFramework client, io.dropwizard.setup.Environment environment, ServiceDescriptor serviceInfo, org.apache.curator.framework.recipes.leader.LeaderLatchListener... listeners)	If you want a ManagedLeaderLatch and you want the standard options (a health check and JAX-RS REST resources) and you might need references to them, use this method to create and start a latch.
static ManagedLeaderLatch	startLeaderLatch(org.apache.curator.framework.CuratorFramework client, io.dropwizard.setup.Environment environment, ServiceDescriptor serviceDescriptor, org.apache.curator.framework.recipes.leader.LeaderLatchListener... listeners)	If the only thing you want is a ManagedLeaderLatch and you want the standard options (a health check and JAX-RS REST resources) and you do not need references to them, use this method to create and start a latch.
ManagedLeaderLatchCreator	withoutHealthCheck()	Configures without a health check.
ManagedLeaderLatchCreator	withoutResources()	Configures without REST resources to check for leadership and if a leader latch is present.

Methods inherited from class java.lang.Object

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

Method Detail

from

public static ManagedLeaderLatchCreator from(org.apache.curator.framework.CuratorFramework client,
                                             io.dropwizard.setup.Environment environment,
                                             ServiceDescriptor serviceDescriptor,
                                             org.apache.curator.framework.recipes.leader.LeaderLatchListener... listeners)

Static factory method to create a ManagedLeaderLatchCreator.

Use this method when you want to perform additional configuration before starting the leader latch.

You will need to call start() on the returned instance in order to start the ManagedLeaderLatch.

Parameters:

client - the Curator client

environment - the Dropwizard environment

serviceDescriptor - service metadata

listeners - optional listeners

Returns:

a new instance

Throws:

IllegalStateException - if the client is not started, or any required arguments are null

startLeaderLatch

public static ManagedLeaderLatch startLeaderLatch(org.apache.curator.framework.CuratorFramework client,
                                                  io.dropwizard.setup.Environment environment,
                                                  ServiceDescriptor serviceDescriptor,
                                                  org.apache.curator.framework.recipes.leader.LeaderLatchListener... listeners)

If the only thing you want is a ManagedLeaderLatch and you want the standard options (a health check and JAX-RS REST resources) and you do not need references to them, use this method to create and start a latch.

Otherwise use start(CuratorFramework, Environment, ServiceDescriptor, LeaderLatchListener...).

Parameters:

client - the Curator client

environment - the Dropwizard environment

serviceDescriptor - the service information from the registry

listeners - optional listeners

Returns:

a started ManagedLeaderLatch

Throws:

IllegalStateException - if the client is not started, or any required arguments are null

See Also:

start(CuratorFramework, Environment, ServiceDescriptor, LeaderLatchListener...)

start

public static ManagedLeaderLatchCreator start(org.apache.curator.framework.CuratorFramework client,
                                              io.dropwizard.setup.Environment environment,
                                              ServiceDescriptor serviceInfo,
                                              org.apache.curator.framework.recipes.leader.LeaderLatchListener... listeners)

If you want a ManagedLeaderLatch and you want the standard options (a health check and JAX-RS REST resources) and you might need references to them, use this method to create and start a latch.

The returned ManagedLeaderLatchCreator can be used to then obtain the ManagedLeaderLatch as well as the health check and listeners.

Parameters:

client - the Curator client

environment - the Dropwizard environment

serviceInfo - the service information from the registry

listeners - optional listeners

Returns:

a ManagedLeaderLatchCreator with a started ManagedLeaderLatch

Throws:

IllegalStateException - if the client is not started, or any required arguments are null

withoutHealthCheck

public ManagedLeaderLatchCreator withoutHealthCheck()

Configures without a health check.

Use only when constructing a new ManagedLeaderLatchCreator.

Returns:

this instance, for method chaining

withoutResources

public ManagedLeaderLatchCreator withoutResources()

Configures without REST resources to check for leadership and if a leader latch is present.

Use only when constructing a new ManagedLeaderLatchCreator.

Returns:

this instance, for method chaining

addLeaderLatchListener

public ManagedLeaderLatchCreator addLeaderLatchListener(org.apache.curator.framework.recipes.leader.LeaderLatchListener listener)

Adds the specified LeaderLatchListener.

Use only when constructing a new ManagedLeaderLatchCreator.

Parameters:

listener - the listener to add

Returns:

this instance, for method chaining

start

public ManagedLeaderLatchCreator start()

Starts the leader latch, performing the following actions:

• Creates a new ManagedLeaderLatch, starts it, and tells the Dropwizard lifecycle to manage (stop) it
• Creates and registers a ManagedLeaderLatchHealthCheck unless explicitly disabled via withoutHealthCheck()
• Creates and registers the JAX-RS REST endpoints unless explicitly disabled via withoutResources()

Note that once this method is called, nothing about the ManagedLeaderLatch can be changed, and calls to other instance methods (e.g. addLeaderLatchListener) will have no effect. Similarly, calling this method more than once is considered unexpected behavior, and we will simply return the existing instance without taking any other actions.

Returns:

this instance, from which you can then retrieve the (started) ManagedLeaderLatch

Throws:

ManagedLeaderLatchException - if an error occurs starting the latch

isLeaderLatchStarted

public boolean isLeaderLatchStarted()

Has this instance created and started a ManagedLeaderLatch?

Returns:

true if this instance has created and started a leader latch

getLeaderLatch

public ManagedLeaderLatch getLeaderLatch()

Returns the ManagedLeaderLatch created after start() has been called.

Use isLeaderLatchStarted() to ensure the latch has been started to ensure this method will succeed.

Returns:

the leader latch

Throws:

IllegalStateException - if called but the latch has not been started yet

getHealthCheck

public Optional<ManagedLeaderLatchHealthCheck> getHealthCheck()

Returns the health check (if registered) after start() has been called.

Returns:

the registered health check

Throws:

IllegalStateException - if called but the latch has not been started yet

getListeners

public List<org.apache.curator.framework.recipes.leader.LeaderLatchListener> getListeners()

Returns a list containing all registered LeaderLatchListeners after start() has been called.

Returns:

any registered LeaderLatchListeners

Throws:

IllegalStateException - if called but the latch has not been started yet

Implementation Note:

The returned list is an unmodifiable list containing the registered listeners