atom feed3 messages in com.marklogic.developer.generalRe: [MarkLogic Dev General] Spawned T...
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Eliot KimberNov 9, 2017 4:06 pm 
Geert JostenNov 9, 2017 9:46 pm 
Eliot KimberNov 10, 2017 7:39 am 
Subject:Re: [MarkLogic Dev General] Spawned Task Appears to Block Other Threads
From:Geert Josten (Geer@marklogic.com)
Date:Nov 9, 2017 9:46:28 pm
List:com.marklogic.developer.general

Hi Eliot,

I think you kicked off your watcher job with an HTTP request, and it keeps the port open until it finishes. Only one thread can use the port at the same time. Use a different port for task response traffic, or consider running your watcher as a scheduled task.

Not super robust, and probably not used in production, but i did write an alternative queque for MarkLogic. It might give you some ideas..

https://github.com/grtjn/ml-queue

Cheers, Geert

On 11/10/17, 1:06 AM, "gene@developer.marklogic.com on behalf of Eliot Kimber" <gene@developer.marklogic.com on behalf of ekim@contrext.com> wrote:

I have a system where I have a ³client² ML server that submits jobs to a set of remote ML servers, checking their task queues and keeping each server¹s queue at a max of 100 queued items (the remote servers could go away without notice so the client needs to be able to restart tasks and not have too many things queued up that would just have to resubmitted).

The remote tasks then talk back to the client to report status and return their final results.

My job submission code use recursive functions to iterate over the set of tasks to be submitted, checking for free remote queue slots via the ML REST API and submitting jobs as the queues empty. This code is spawned into a separate task in the task server. It uses xdmp:sleep(1000) to pause between checking the job queues.

This all works fine, in that my jobs are submitted correctly and the remote queues fill up.

However, as long as the job-submission task in the task server is running, the HTTP app that handles the REST calls from the remote servers is blocked (which blocks the remote jobs, which are of course waiting for responses from the client).

If I kill the task server task, then the remote responses are handled as I would expect.

My question: Why would the task server task block the other app? There must be something I¹m doing or not doing but I have no idea what it might be.