Greetings!
In our app, we have a lot of batch “jobs”, each of which stands up an RPC
service on a unique queue. However, when jobs quit, clients may still try to
communicate and I don’t want this to hang, I want clients to see an error
reply. To this end, I am implementing a “fallback” service for ended-job RPC
queues, of which there can be 100s, that returns errors. This is expected to
be very low traffic and the polling can be done infrequently (like every few
seconds), so performance doesn’t matter.
The queues are set to auto-delete, and in order to keep broker memory down, I
don’t want to do anything to prevent auto-deletion. Because in most cases,
nothing will be posted to these queues. I want to use a strategy like this:
* Enumerate queues first, to see which ones exist.
* Of the queues that exist, use the queue-based management API to get a
message count (see method below).
* Only for queues that have a non-zero message count, create a consumer and
call receive() to poll for messages.
Will this strategy avoid interfering with the broker’s auto-delete?
Is queue enumeration low-impact enough to call it every few seconds?
Method used for getting queue count (this is all using the
artemis-jms-client-all JMS client):
public int getQueueEntryCount(String queueName) {
return getIntAttribute(queueName, "MessageCount");
}
private int getIntAttribute(final String queueName, final String attributeName)
{
String resourceName = ResourceNames.QUEUE + queueName;
synchronized (lock) {
ClientRequestor client = getClient();
try {
ClientMessage request = clientSession.createMessage(false);
ManagementHelper.putAttribute(request, resourceName, attributeName);
ClientMessage reply = client.request(request);
if (ManagementHelper.hasOperationSucceeded(reply)) {
return (int)(long)ManagementHelper.getResult(reply, Long.class);
} else {
// Because we cannot tell the difference between queue-does-not-exist
and a real error
return 0;
}
}
catch (Exception e) {
throw new RuntimeException("Error fetching " + attributeName + " for
queue " + queueName, e);
}
}
}
Thanks
John
[rg] <https://www.redpointglobal.com/>
John Lilley
Data Management Chief Architect, Redpoint Global Inc.
888 Worcester Street, Suite 200 Wellesley, MA 02482
M: +1 7209385761<tel:+1%207209385761> |
[email protected]<mailto:[email protected]>
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