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POTail file into message queue
 

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  1. POTail file into message queue
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    <p>I launch a process on a linux machine via python's subprocess (specifically on AWS EC2) which generates a number of files. I need to "tail -f" these files and send each of the resulting jsonified outputs to their respective AWS SQS queues. How would I go about such a task?</p> <p><strong>Edit</strong></p> <p>As suggested by this answer, <a href="https://stackoverflow.com/questions/636561/how-can-i-run-an-external-command-asynchronously-from-python/636719#636719" title="asyncproc">asyncproc</a>, and <a href="http://www.python.org/dev/peps/pep-3145/" rel="nofollow noreferrer">PEP3145</a>, I can do this with the following:</p> <pre><code>from asyncproc import Process import Queue import os import time # Substitute AWS SQS for Queue sta_queue = Queue.Queue() msg_queue = Queue.Queue() running_procs = {'status':(Process(['/usr/bin/tail', '--retry', '-f','test.sta']),sta_queue),'message':(Process(['/usr/bin/tail', '--retry', '-f', 'test.msg' ]),msg_queue)} def handle_proc(p,q): latest = p.read() if latest: # If nothing new, latest will be an empty string q.put(latest) retcode = p.wait(flags=os.WNOHANG) return retcode while len(running_procs): proc_names = running_procs.keys() for proc_name in proc_names: proc, q = running_procs[proc_name] retcode = handle_proc(proc, q) if retcode is not None: # Process finished. del running_procs[proc_name] time.sleep(1.0) print("Status queue") while not sta_queue.empty(): print(sta_queue.get()) print("Message queue") while not msg_queue.empty(): print(msg_queue.get()) </code></pre> <p>This should be sufficient, I think, unless others can provide a better answer.</p> <p><strong>More Edits</strong></p> <p>I'm overthinking the problem. Although the above works nicely, I think the simplest solution is: -check for the existence of the files -if the files exist, copy them to a bucket on AWS S3 and send a message through AWS SQS that files have been copied. Repeat every 60 seconds -consumer app polls SQS and eventually receives message that files have been copied -consumer app downloads files from S3 and replaces the previous contents with the latest contents. Repeat until job completes</p> <p>Although the whole issue of asynchronous IO in subprocess is still an issue. </p>
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    1. COAre you sure you wouldn't rather use a FIFO, or a FD directly into the process?
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      1. USIgnacio Vazquez-Abrams
 

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