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https://issues.apache.org/jira/browse/QUARKS-8?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15194042#comment-15194042
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ASF GitHub Bot commented on QUARKS-8:
-------------------------------------

Github user vdogaru commented on a diff in the pull request:

    https://github.com/apache/incubator-quarks/pull/9#discussion_r56067001
  
    --- Diff: 
samples/topology/src/main/java/quarks/samples/topology/JobPollingSample.java ---
    @@ -0,0 +1,130 @@
    +/*
    +Licensed to the Apache Software Foundation (ASF) under one
    +or more contributor license agreements.  See the NOTICE file
    +distributed with this work for additional information
    +regarding copyright ownership.  The ASF licenses this file
    +to you under the Apache License, Version 2.0 (the
    +"License"); you may not use this file except in compliance
    +with the License.  You may obtain a copy of the License at
    +
    +  http://www.apache.org/licenses/LICENSE-2.0
    +
    +Unless required by applicable law or agreed to in writing,
    +software distributed under the License is distributed on an
    +"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    +KIND, either express or implied.  See the License for the
    +specific language governing permissions and limitations
    +under the License.
    +*/
    +package quarks.samples.topology;
    +
    +import java.util.ArrayList;
    +import java.util.List;
    +import java.util.Random;
    +import java.util.concurrent.Callable;
    +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 quarks.execution.Job;
    +import quarks.execution.JobRegistryService;
    +import quarks.providers.development.DevelopmentProvider;
    +import quarks.runtime.etiao.JobRegistry;
    +import quarks.topology.TStream;
    +import quarks.topology.Topology;
    +
    +/**
    + * Job monitoring by polling job state. 
    + * <p>
    + * Demonstrates job monitoring using the {@link JobRegistryService} 
service.
    + * The example starts a system monitoring application then concurrently 
    + * submits two jobs.  The monitoring application is using a polling source
    + * to periodically scan the job registry and generates tuples containing 
the 
    + * current state of registered jobs. Tuples are pushed to a sink which 
prints
    + * them onto the system output.
    + */
    +public class JobPollingSample {
    +    private final DevelopmentProvider dtp;
    +    
    +    public static void main(String[] args) throws Exception {
    +        
    +        JobPollingSample app = new JobPollingSample();
    +
    +        // Start monitoring app
    +        app.monitor();
    +
    +        Thread.sleep(2000);
    +
    +        // Asynchronously start two jobs
    --- End diff --
    
    Right, I intend to replace this sample with a system application which uses 
an events source rather than polling to demonstrate the correct way for 
monitoring jobs.  Any inline sleeps a inserted to simulate a real case 
scenario, I'll properly document them.


> Restart topology on uncaught exception
> --------------------------------------
>
>                 Key: QUARKS-8
>                 URL: https://issues.apache.org/jira/browse/QUARKS-8
>             Project: Quarks
>          Issue Type: New Feature
>          Components: Runtime
>            Reporter: Victor Dogaru
>            Assignee: Victor Dogaru
>              Labels: failure-recovery
>
> If a Quarks thread abruptly terminates due to an uncaught exception the 
> runtime shuts down. 
> A mechanism is needed to prevent the Quarks application from becoming 
> unavailable:
> * Have a monitor service which resubmits the topology in case it shuts down.
> * Restart the failed oplet. In the ETIAO runtime, a source and all downstream 
> oplet invocations (up to an Isolate) will execute in the same thread, so the 
> runtime needs to restart the failed path.



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