com.netflix.turbine.discovery

Class InstanceObservable

java.lang.Object

com.netflix.turbine.discovery.InstanceObservable

public class InstanceObservable
extends java.lang.Object

Class the represents a continuous poller that fetches Instance information from the specified InstanceDiscovery object. The InstanceDiscovery must be registered with the PluginsFactory at startup, else Turbine uses a default FileBasedInstanceDiscovery mechanism. Note that the InstanceObservable runs in continuous loop at a periodic interval specified by the config property turbine.discovery.pollDelayMillis with a default of 60 seconds

It checks the Instance.isUp() state to understand whether to notify observers downstream about hosts that are up and down.

It also keeps state from the previous poll and it uses this to determine whether some older hosts have disappeared.

One can register a InstanceObservable.InstanceObserver by using the register(InstanceObserver) to receive periodic updates of hosts that are up and down via the InstanceObservable.InstanceObserver.hostsUp(Collection) and the InstanceObservable.InstanceObserver.hostsDown(Collection) callbacks.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	InstanceObservable.InstanceObserver Interface for representing an observer to the InstanceObservable
static class	InstanceObservable.UnitTest

Method Summary

Methods

Modifier and Type	Method and Description
void	deregister(InstanceObservable.InstanceObserver watcher) Deregister from the observable
int	getCurrentHostDownCount()
java.util.HashSet<Instance>	getCurrentHostsDown()
java.util.HashSet<Instance>	getCurrentHostsUp()
int	getCurrentHostUpCount()
int	getHeartbeat()
static InstanceObservable	getInstance()
int	getNumHostsUpForCluster(java.lang.String cluster) Helper method to give us the hosts up for a specified cluster
java.util.Set<java.lang.String>	getObservers()
InstanceObservable.InstanceObserver	register(InstanceObservable.InstanceObserver watcher) Register with the observable to get callbacks on fleet status updates
void	start(InstanceDiscovery iDiscovery) Idempotent call to start the Observable.
void	stop() Stop the InstanceObservable

Methods inherited from class java.lang.Object

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

Method Detail

getInstance

public static InstanceObservable getInstance()

Returns:

InstanceObservable

getCurrentHostUpCount

@Monitor(name="HostUp",
         type=GAUGE)
public int getCurrentHostUpCount()

getCurrentHostsUp

public java.util.HashSet<Instance> getCurrentHostsUp()

Returns:

HashSet<Instance>

getCurrentHostDownCount

@Monitor(name="HostDown",
         type=GAUGE)
public int getCurrentHostDownCount()

getHeartbeat

@Monitor(name="Heartbeat",
         type=COUNTER)
public int getHeartbeat()

getCurrentHostsDown

public java.util.HashSet<Instance> getCurrentHostsDown()

Returns:

HashSet<Instance>

getObservers

public java.util.Set<java.lang.String> getObservers()

Returns:

Set

start

public void start(InstanceDiscovery iDiscovery)

Idempotent call to start the Observable. Caller must provide the InstanceDiscovery implementation

Parameters:

iDiscovery -

stop

public void stop()

Stop the InstanceObservable

register

public InstanceObservable.InstanceObserver register(InstanceObservable.InstanceObserver watcher)

Register with the observable to get callbacks on fleet status updates

Parameters:

watcher - InstanceObservable.InstanceObserver

Returns:

InstanceObservable.InstanceObserver if it already exists

deregister

public void deregister(InstanceObservable.InstanceObserver watcher)

Deregister from the observable

Parameters:

watcher - InstanceObservable.InstanceObserver

getNumHostsUpForCluster

public int getNumHostsUpForCluster(java.lang.String cluster)

Helper method to give us the hosts up for a specified cluster

Parameters:

cluster -

Returns:

int