There are a number of steps involved here. 1. The primary playbook process spawns a worker 2. The worker executes the async_wrapper for the command module 3. The async_wrapper forks to daemonize 4. The async_wrapper executes the transferred module 5. The actual module is contained within what we call AnsiballZ which is a compressed archive, and it extracts and executes the actual python code 6. Actual module executing.
`forks` only limits how many workers can be launched by the primary playbook process, not how many processes will be spawned as a result of the worker. On Thu, Jun 11, 2020 at 7:01 AM Jagadeeshkumar Dittakavi < [email protected]> wrote: > @Matt, > > Got another question in concurrency support in Ansible. > Is there any way to limit the number of processes that could be spawned on > a given host? > My requirement is not to execute the commands/scripts remotely. In my > case, the whole play needs to be executed on locahost only. > I have tried a simple test program and noticed that there are as many as 6 > processes are spawned to execute 'sleep 20' asynchronously. > > Please kindly revert. Thank you inadvance. > > *Command:* ansible-playbook test_playbook.yml --forks=1 > > > > *Processes:* > > root 69484 34309 9 04:50 pts/10 00:00:00 /usr/bin/python2 > /usr/bin/*ansible*-playbook test_playbook.yml --forks=1 > > root 69509 1 0 04:50 ? 00:00:00 /usr/bin/python2 /root/. > *ansible*/tmp/*ansible*-tmp-1591876209.82-38354017880191/async_wrapper.py > 198806654079 50 > /root/.*ansible*/tmp/*ansible*-tmp-1591876209.82-38354017880191/command.py > _ > > root 69510 69509 0 04:50 ? 00:00:00 /usr/bin/python2 /root/. > *ansible*/tmp/*ansible*-tmp-1591876209.82-38354017880191/async_wrapper.py > 198806654079 50 > /root/.*ansible*/tmp/*ansible*-tmp-1591876209.82-38354017880191/command.py > _ > > root 69511 69510 0 04:50 ? 00:00:00 /usr/bin/python2 /root/. > *ansible*/tmp/*ansible*-tmp-1591876209.82-38354017880191/command.py > > root 69512 69511 1 04:50 ? 00:00:00 /usr/bin/python2 /tmp/ > *ansible*_f9ckPD/*ansible*_module_command.py > > root 69520 69484 3 04:50 pts/10 00:00:00 /usr/bin/python2 > /usr/bin/*ansible*-playbook test_playbook.yml --forks=1 > > > > > > *Code:* > > [root@oracle-siha file_copy_test]# cat test_playbook.yml > > - name: Testing processes > > gather_facts: no > > hosts: localhost > > tasks: > > - name: run sleep command > > async: 50 > > poll: 0 > > command: sleep 20 > > register: res > > - name: wait for the completion > > async_status: > > jid: "{{ res.ansible_job_id }}" > > register: output > > until: output.finished > > delay: 5 > > retries: 10 > > > > On Friday, June 5, 2020 at 9:50:19 AM UTC+5:30, Jagadeeshkumar Dittakavi > wrote: >> >> Thank you Matt for the detailed and quick reply.. Much appreciated the >> support from the community. >> >> On Friday, June 5, 2020 at 12:29:30 AM UTC+5:30, Matt Martz wrote: >>> >>> Yes, it would utilize the threading library in Python. The GIL is a >>> primary cause to the CPU restrictions. Our main process that orchestrates >>> all of the task executions is already heavily CPU bound, so adding >>> additional threads to the same core can cause a decrease in performance. >>> Assuming we create a process model plugin type, other process models are >>> possible, such as using asyncio, concurrent.futures, gevent, etc. But I >>> don't expect this work to be complete any time soon. >>> >>> So for now, consider forking the only process model for the near future. >>> >>> On Thu, Jun 4, 2020 at 1:51 PM Jagadeeshkumar Dittakavi < >>> [email protected]> wrote: >>> >>>> Thank you for the prompt reply.. Just a curious question: Is the >>>> threading work that is underway based on python threads or pthreads or any >>>> other threading mechanism? As you mentioned that the threading model is not >>>> going to be performant, was the reason being the python's GIL? >>>> >>>> >>>> On Friday, June 5, 2020 at 12:01:14 AM UTC+5:30, Matt Martz wrote: >>>>> >>>>> The only current process model is forking. There has been some work >>>>> done to add a threaded process model, but there are some large hurdles to >>>>> overcome. >>>>> >>>>> In practice, it is not necessarily more performant, and in many cases >>>>> it was less performant, as it causes more CPU contention on a single core >>>>> that is already resource constrained. >>>>> >>>>> On Thu, Jun 4, 2020 at 1:18 PM Jagadeeshkumar Dittakavi < >>>>> [email protected]> wrote: >>>>> >>>>>> I am a newbie to ansible but I got to explore how to run a tasks in >>>>>> parallel by spawing a thread for each task instead of a process. My >>>>>> requirement is to run the playbook on my localhost and there is no remote >>>>>> task execution needed. >>>>>> I also would like to wait for all threads to complete before I move >>>>>> on to a task that has to be serialised. >>>>>> >>>>>> Can I chose thread vs process when it comes to parallel task >>>>>> execution? >>>>>> If it is possible to spawn threads from ansible, are they equivalent >>>>>> to python greenthreads or pthreads or something else? >>>>>> >>>>>> Thank you in advance! >>>>>> >>>>>> >>>>>> -- >>>>>> You received this message because you are subscribed to the Google >>>>>> Groups "Ansible Project" group. >>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>> send an email to [email protected]. >>>>>> To view this discussion on the web visit >>>>>> https://groups.google.com/d/msgid/ansible-project/0d59cf96-b053-4390-8dbb-663c70403104o%40googlegroups.com >>>>>> <https://groups.google.com/d/msgid/ansible-project/0d59cf96-b053-4390-8dbb-663c70403104o%40googlegroups.com?utm_medium=email&utm_source=footer> >>>>>> . >>>>>> >>>>> >>>>> >>>>> -- >>>>> Matt Martz >>>>> @sivel >>>>> sivel.net >>>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "Ansible Project" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to [email protected]. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/ansible-project/48f0ed5f-83c7-4bf4-a991-94ec78ce832eo%40googlegroups.com >>>> <https://groups.google.com/d/msgid/ansible-project/48f0ed5f-83c7-4bf4-a991-94ec78ce832eo%40googlegroups.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>> >>> >>> -- >>> Matt Martz >>> @sivel >>> sivel.net >>> >> -- > You received this message because you are subscribed to the Google Groups > "Ansible Project" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/ansible-project/f0093a03-d20b-4187-8bca-913e10770f5fo%40googlegroups.com > <https://groups.google.com/d/msgid/ansible-project/f0093a03-d20b-4187-8bca-913e10770f5fo%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- Matt Martz @sivel sivel.net -- You received this message because you are subscribed to the Google Groups "Ansible Project" group. 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