Elekt Consul

Elekt is a Java lib for leadership election. Elekt Consul uses Consul to do leadership election.

(This project was called Czar Maker Consul but changed. We have Reflekt, Reakt, Conekt and now Elekt.)

Getting Started

Maven

<dependency>
    <groupId>io.advantageous.elekt</groupId>
    <artifactId>elekt-consul</artifactId>
    <version>0.1.0.RELEASE</version>
</dependency>

Gradle

compile 'io.advantageous.elekt:elekt-consul:0.1.0.RELEASE'

Sample usage

import io.advantageous.consul.Consul;
import io.advantageous.elekt.Endpoint;
import io.advantageous.elekt.consul.*;
import io.advantageous.qbit.util.TestTimer;
import io.advantageous.reakt.promise.Promise;
import io.advantageous.reakt.promise.Promises;
import io.advantageous.reakt.reactor.Reactor;
import io.advantageous.reakt.reactor.TimeSource;

...

    private final long sessionTTL = 10;
    private final long newLeaderCheckInterval = 5;
    private ConsulLeadershipElector leadershipElector;
    private Reactor reactor;
    private TestTimer testTimer;
    private Consul consul;

...
        consul = Consul.consul();
        testTimer = new TestTimer();
        testTimer.setTime();
        reactor = Reactor.reactor(Duration.ofSeconds(30), new TestTimeSource(testTimer));
        final String serviceName = "foo";

        ConsulLeadershipProvider provider = new ConsulLeadershipProvider(serviceName, consul, TimeUnit.SECONDS, sessionTTL);

        leadershipElector = new ConsulLeadershipElector(provider, serviceName, reactor, TimeUnit.SECONDS,
                sessionTTL, newLeaderCheckInterval);


        /** Get the current leader. */
        Promise<Endpoint> promise = Promises.<Endpoint>blockingPromise();
        leadershipElector.getLeader(promise);

        assertTrue(promise.expect().isEmpty());


        /** Elect this endpoint as the current leader. */
        Promise<Boolean> selfElectPromise = Promises.<Boolean>blockingPromise();
        leadershipElector.selfElect(new Endpoint("foo.com", 9091), selfElectPromise);

        assertTrue("We are now the leader", selfElectPromise.get());


        /** Get the current leader again.  */
        Promise<Endpoint> getLeaderPromise = Promises.<Endpoint>blockingPromise();
        leadershipElector.getLeader(getLeaderPromise);

        /** See if it present. */
        assertTrue(getLeaderPromise.expect().isPresent());

        /** See if it has the host foo.com. */
        assertEquals("foo.com", getLeaderPromise.get().getHost());

        /** See if the port is 9091. */
        assertEquals(9091, getLeaderPromise.get().getPort());

        testTimer.seconds(100);

        leadershipElector.process();

        /** Elect a new leader. */
        leadershipElector.selfElect(new Endpoint("foo2.com", 9092), selfElectPromise);