samples/topology/src/main/java/org/apache/edgent/samples/topology/JobEventsSample.java

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package org.apache.edgent.samples.topology;

import java.util.Random;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

import org.apache.edgent.execution.Job;
import org.apache.edgent.execution.services.JobRegistryService;
import org.apache.edgent.providers.direct.DirectProvider;
import org.apache.edgent.runtime.jobregistry.JobEvents;
import org.apache.edgent.runtime.jobregistry.JobRegistry;
import org.apache.edgent.topology.TStream;
import org.apache.edgent.topology.Topology;

import com.google.gson.JsonObject;

/**
 * Demonstrates job monitoring using the {@link JobRegistryService} service.
 * <p>
 * The example starts a system monitoring application, then concurrently 
 * submits two jobs.
 * The job monitoring application generates job event tuples when jobs 
 * are added or removed from registry, or when a job gets updated. 
 * Tuples are pushed to a sink, which prints them onto the system output.</p>
 * <p>
 * Note that the original job events stream processing is executed by the
 * JobRegistryService event {@linkplain 
 * JobRegistryService#addListener(org.apache.edgent.function.BiConsumer) listeners}
 * invoker thread. 
 * It is considered good practice to isolate the event source from the rest 
 * of the graph, in order for the processing of tuples to be executed by a
 * different thread.</p>
 */
public class JobEventsSample {
    private final DirectProvider dp;

    public static void main(String[] args) throws Exception {
        
        JobEventsSample sample = new JobEventsSample();
        ScheduledExecutorService executor = Executors.newScheduledThreadPool(2);

        // Monitoring app
        sample.startJobMonitorApp();

        // Asynchronously start two applications
        executor.schedule(sample.runMonitoredApp("MonitoredApp1"), 300, TimeUnit.MILLISECONDS);
        executor.schedule(sample.runMonitoredApp("MonitoredApp2"), 3000, TimeUnit.MILLISECONDS);
    }

    JobEventsSample() throws Exception {
        this.dp = new DirectProvider();
        JobRegistry.createAndRegister(dp.getServices());
    }

    /**
     * Declares and submits a monitored application.
     * <p>
     * Note that inline sleeps are introduced to simulate the timing 
     * of a real-life application lifecycle.
     * 
     * @param name application name
     */
    void monitored(String name) throws InterruptedException, ExecutionException {
        // Declare topology
        Topology t = dp.newTopology(name);
        
        Random r = new Random();
        TStream<Double> d  = t.poll(() -> r.nextGaussian(), 100, TimeUnit.MILLISECONDS);
        d.sink(tuple -> System.out.print("."));

        // Submit job after 2 seconds
        Thread.sleep(2000);
        Future<Job> f = dp.submit(t);
        Job job = f.get();
        
        // Run for 5 seconds, then close job
        Thread.sleep(5000);
        job.stateChange(Job.Action.CLOSE);

        // Unregister job after 2 seconds
        Thread.sleep(2000);
        provider().getServices().getService(JobRegistryService.class).removeJob(job.getId());
    }

    /**
     * Monitoring application generates tuples on job registrations, removals, 
     * and on registered job updates.
     */
    Job startJobMonitorApp() throws InterruptedException, ExecutionException {
        Topology topology = dp.newTopology("JobMonitorApp");

        TStream<JsonObject> jobEvents = JobEvents.source(
                topology, 
                (evType, job) -> { return JobEventsSample.wrap(evType, job); });

        jobEvents.sink(tuple -> {
                System.err.println(tuple.toString());
            });

        Future<Job> f = dp.submit(topology);
        return f.get();
    }
    
    /**
     * Creates a JsonObject wrapping a JobRegistryService event type and 
     * Job info.
     * 
     * @param evType the event type
     * @param job the job
     * @return the wrapped data
     */
    static JsonObject wrap(JobRegistryService.EventType evType, Job job) {
        JsonObject value = new JsonObject();
        value.addProperty("time", (Number)System.currentTimeMillis());
        value.addProperty("event", evType.toString());
        JsonObject obj = new JsonObject();
        obj.addProperty("id", job.getId());
        obj.addProperty("name", job.getName());
        obj.addProperty("state", job.getCurrentState().toString());
        obj.addProperty("nextState", job.getNextState().toString());
        obj.addProperty("health", job.getHealth().toString());
        obj.addProperty("lastError", job.getLastError());
        value.add("job", obj);
        return value;
    }

    private DirectProvider provider() {
        return dp;
    }
    
    private Runnable runMonitoredApp(String name) {
        return new Runnable() {

            @Override
            public void run() {
                try {
                    monitored(name);
                } catch (Throwable t) {
                    throw new RuntimeException(t);
                }
            }
        };
    }
}