Pipelining is a *significant* performance benefit, because each task can
be completed with a single SSH connection (vs. one ssh connection at the
start to mkdir, plus one sftp and one ssh per task).
Pipelining is disabled by default in Ansible because it conflicts with
the use of sudo if 'Defaults requiretty' is set in /etc/sudoers (as it
is on Red Hat) and su (which always requires a tty).
We can (and already do) make sudo/su happy by using "ssh -t" to allocate
a tty, but then the python interpreter goes into interactive mode and is
unhappy with module source being written to its stdin, per the following
comment from connections/ssh.py:
# we can only use tty when we are not pipelining the modules.
# piping data into /usr/bin/python inside a tty automatically
# invokes the python interactive-mode but the modules are not
# compatible with the interactive-mode ("unexpected indent"
# mainly because of empty lines)
Instead of the (current) drastic solution of turning off pipelining when
we use a tty, we can instead use a tty but suppress the behaviour of the
Python interpreter to switch to interactive mode. The easiest way to do
this is to make its stdin *not* be a tty, e.g. with cat|python.
This works, but there's a problem: ssh will ignore -t if its input isn't
really a tty. So we could open a pseudo-tty and use that as ssh's stdin,
but if we then write Python source into it, it's all echoed back to us
(because we're a tty). So we have to use -tt to force tty allocation; in
that case, however, ssh puts the tty into "raw" mode (~ICANON), so there
is no good way for the process on the other end to detect EOF on stdin.
So if we do:
echo -e "print('hello world')\n"|ssh -tt someho.st "cat|python"
…it hangs forever, because cat keeps on reading input even after we've
closed our pipe into ssh's stdin. We can get around this by writing a
special __EOF__ marker after writing in_data, and doing this:
echo -e "print('hello world')\n__EOF__\n"|ssh -tt someho.st "sed -ne '/__EOF__/q' -e p|python"
This works fine, but in fact I use a clever python one-liner by mgedmin
to achieve the same effect without depending on sed (at the expense of a
much longer command line, alas; Python really isn't one-liner-friendly).
We also enable pipelining by default as a consequence.
* Fix the task_vars parameter to not default to a mutable type (dict)
* Implement invocation in the base class's run() method have each action
module call the run() method's implemention in the base class.
* Return values from the action plugins' run() method takes the return
value from the base class run() method into account so that invocation
makes its way to the output.
Fixes#12869
Revert "Remove auto-added invocation return value as it is not used by v2 and could leak sensitive data."
This reverts commit 6ce6b20268.
Remove the note that invocation was removed as we've now restored it.
Revert "keyword not in ubuntu 14.04"
This reverts commit 5c01622457.
Revert "remove invocation keyword check"
This reverts commit 5177cb3f74.
SSH pipelining can be a significant performance improvement, but it will
not work if sudoers is configured to requiretty. With this change, one
could have pipelining enabled in ansible.cfg, but use sudo to turn off
requiretty in a separate play (or task) where pipelining is disabled:
- hosts: foo
vars:
ansible_pipelining: no
tasks:
- lineinfile: dest=/etc/sudoers line='Defaults requiretty' state=absent
sudo_user: root
(Note that sudoers has a complicated syntax, so the above lineinfile
invocation may be too simplistic for production use; but the point is
that a separate play can do something to disable requiretty.)
* allow global no_log setting, no need to set at play or task level, but can be overriden by them
* allow turning off syslog only on task execution from target host (manage_syslog), overlaps with no_log functionality
* created log function for task modules to use, now we can remove all syslog references, will use systemd journal if present
* added debug flag to modules, so they can make it call new log function conditionally
* added debug logging in module's run_command
Luca Berruti
Toshio Kuratomi
nitzmahone
Abhijit Menon-Sen
Brian Coca
Brian Coca
James Cammarata
Yannig Perré
Sebastien Couture
Toshio Kuratomi
Joern Heissler
Rene Moser
Jason O'Donnell
Petr Mifek