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docs: fix up incomplete Temporary Files section.

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David Wilson 2018-10-23 16:53:06 +01:00
parent cfcc7c0273
commit 72da291b24
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docs/ansible.rst
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@ -427,11 +427,9 @@ specific variables with a particular linefeed style.
Temporary Files
~~~~~~~~~~~~~~~
Temporary file handling in Ansible is incredibly tricky business, and the exact
behaviour varies across major releases.
Ansible creates a variety of temporary files and directories depending on its
operating mode.
Temporary file handling in Ansible is tricky, and the precise behaviour varies
across major versions. A variety of temporary files and directories are
created, depending on the operating mode:
In the best case when pipelining is enabled and no temporary uploads are
required, for each task Ansible will create one directory below a
@ -470,19 +468,19 @@ In summary, for each task Ansible may create one or more of:
Mitogen for Ansible
^^^^^^^^^^^^^^^^^^^
Temporary h
Temporary directory handling is fiddly and varies across major Ansible
releases.
As Mitogen can execute new-style modules from RAM, and transfer files to target
user accounts without first writing an intermediary file in any separate login
account, handling is relatively simplified.
Temporary directories must exist to maintain compatibility with Ansible, as
many modules introspect :data:`sys.argv` to find a directory where they may
write files, however only one directory exists for the lifetime of each
interpreter, its location is consistent for each target account, and it is
always privately owned by that account.
interpreter, its location is consistent for each account, and it is always
privately owned by that account.
The paths below are tried until one is found that is writeable and lives on a
filesystem with ``noexec`` disabled:
During startup, the persistent remote interpreter tries the paths below until
one is found that is writeable and lives on a filesystem with ``noexec``
disabled:
1. ``$variable`` and tilde-expanded ``remote_tmp`` setting from
``ansible.cfg``
@ -496,10 +494,35 @@ filesystem with ``noexec`` disabled:
8. ``/usr/tmp``
9. Current working directory
The directory is created once at startup, and subdirectories are automatically
created and destroyed for every new task. Management of subdirectories happens
on the controller, but management of the parent directory happens entirely on
the target.
The directory is created at startup and recursively destroyed during interpeter
shutdown. Subdirectories are automatically created and destroyed by the
controller for each task that requires them.
Round-trip Avoidance
^^^^^^^^^^^^^^^^^^^^
Mitogen avoids many round-trips due to temporary file handling that are present
in regular Ansible:
* During task startup, it is not necessary to wait until the target has
succeeded in creating a temporary directory. Instead, any failed attempt to
create the directory will cause any subsequent RPC belonging to the same task
to fail with the error that occurred.
* As temporary directories are privately owned by the target user account,
operations relating to modifying the directory to support cross-account
access are avoided.
* An explicit work-around is included to avoid the `copy` and `template`
actions needlessly triggering a round-trip to set their temporary file as
executable.
* During task shutdown, it is not necessary to wait to learn if the target has
succeeded in deleting a temporary directory, since any error that may occur
can is logged asynchronously via the logging framework, and the persistent
remote interpreter arranges for all subdirectories to be destroyed during
interpreter shutdown.
.. _ansible_process_env: