'shell' module gets 'stuck' in Docker container with this task configuration.

[James Stephenson]

Hi,

This has been driving me mad :).

• Ansible 2.0.2
• Ubuntu 14.04

The following task 'hangs' whilst executing in a Docker container:

shell: >
  echo $(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 16 | head -n 1)
  > {{ arbitrary_file_path }}
args:
  executable: /bin/bash

If I get a shell in the same container (whilst it's hung running the task), and either run the command directly or run:

ansible 127.0.0.1 -c local -m shell -a "echo $(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 16 | head -n 1) > foo_file executable=/bin/bash"

It works as expected!

If I take a look at the processes whilst it's hung, I get (truncated on the right):

USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND

root         1  0.0  0.0   4448   800 ?        Ss   10:18   0:00 /bin/sh -c /srv/provisioning/entrypoint.sh

root         7  0.0  0.0  17968  2868 ?        S    10:18   0:00 /bin/bash /srv/provisioning/entrypoint.sh

root         8  8.9  0.1  82740 26568 ?        R    10:18   0:14 python /usr/bin/ansible-playbook /srv/provisioning/playbook.yml -c local

root        11  8.8  0.1 155768 23084 ?        Sl   10:18   0:13 python /usr/bin/ansible-playbook /srv/provisioning/playbook.yml -c local

root       735  0.0  0.1  97004 25064 ?        S    10:20   0:00 python /usr/bin/ansible-playbook /srv/provisioning/playbook.yml -c local

root       742  0.0  0.0   4448   804 ?        S    10:20   0:00 /bin/sh -c /bin/sh -c 'LANG=en_US.UTF-8 LC_ALL=en_US.UTF-8 LC_MESSAGES=en_US.UTF-

root       743  0.0  0.0   4448   688 ?        S    10:20   0:00 /bin/sh -c LANG=en_US.UTF-8 LC_ALL=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8 /usr/bin/p

root       744  0.0  0.0  34820 11812 ?        S    10:20   0:00 /usr/bin/python /home/tru/.ansible/tmp/ansible-tmp-1461234012.13-9745977883185/co

root       745  0.0  0.0  17964  2900 ?        S    10:20   0:00 /bin/bash -c echo $(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 16 | head -n 

root       746  0.0  0.0  17972  2184 ?        S    10:20   0:00 /bin/bash -c echo $(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 16 | head -n 

root       747 90.3  0.0   4368   668 ?        R    10:20   1:07 cat /dev/urandom

root       748  5.8  0.0   4376   772 ?        S    10:20   0:04 tr -dc a-zA-Z0-9

root       749  2.2  0.0   4360   708 ?        S    10:20   0:01 fold -w 16

Which makes it look like the final 'head' in the piped chain isn't terminating the cat like it typically would. Why that is, I don't know.

Perhaps this makes sense to someone?

Thanks in advance,

JS