Can I change an Esper bolt statement on the fly?

Question

I'm using storm to process some data streams.

At the beginning I read an xml file where I find statements used in Esper bolts. Soon after I define my topology and run it on a cluster. Now, if I want to change a statement in a bolt, I have to modify the xml, stop the cluster, and restart it from the beginning.

Is possible a scenery that sees a thread that checks my xml and when finds new statements defined can update the Esper Bolt with the new statement while the cluster is going on?

I defined an Esper bolt as follows:

    String statement = "select count(*) as userPerMinutes from event.win:time_batch(60 sec)";
    EsperBolt esperBolt = new EsperBolt.Builder()
        .inputs().aliasComponent("user")
        .withField("field1").ofType(String.class)
        .withField("field2").ofType(Integer.class)
        .withField("field3").ofType(Long.class)
        .toEventType("event")
        .outputs().onDefaultStream().emit("userPerMinutes")
        .statements().add(statement)
        .build();

In a thread how can I access to this bolt and edit/add/remove its statement? Through the topology? And how?

Answer 1

I have a similar system. Using storm + esper to run a distributed event process system. Esper can remove and add epl at runtime. How my system does so is, start a new thread in bolt to sync epl from a database from time to time. Update the changed one (remove and then add).

Hope this helps.

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add code might be useful

EPStatement statement = esperAdmin.getStatement(rule.getName());
if (statement != null) {
    statement.destroy();
}