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mitogen/docs/changelog.rst

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.. _changelog:
Release Notes
=============
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v0.2.3 (2018-07-??)
-------------------
* `#315 <https://github.com/dw/mitogen/pull/315>`_: Mitogen for Ansible is
supported under Ansible 2.6. Contributed by `Dan Quackenbush
<https://github.com/danquack>`_.
v0.2.2 (2018-07-??)
-------------------
Mitogen for Ansible
~~~~~~~~~~~~~~~~~~~
* `#291 <https://github.com/dw/mitogen/issues/291>`_: ``ansible_*_interpreter``
variables are parsed using a restrictive shell-like syntax, supporting a
common idiom where ``ansible_python_interpreter`` is set to ``/usr/bin/env
python``.
* `#299 <https://github.com/dw/mitogen/issues/299>`_: fix the ``network_cli``
connection type when the Mitogen strategy is active. Mitogen cannot help
network device connections, however it should still be possible to use device
connections while Mitogen is active.
* `#300 <https://github.com/dw/mitogen/issues/300>`_: an exception could appear
on OS X during shutdown due to scheduling pending Kevent filter changes for
file descriptors that have already been closed before the IO loop resumes. As
a temporary workaround, Mitogen does not make use of Kevent's bulk change
feature.
* `#301 <https://github.com/dw/mitogen/pull/301>`_: variables like ``$HOME`` in
the ``remote_tmp`` setting are evaluated correctly.
* `#303 <https://github.com/dw/mitogen/pull/303>`_: the ``doas`` become method
is supported. Contributed by `Mike Walker
<https://github.com/napkindrawing>`_.
* `#309 <https://github.com/dw/mitogen/issues/309>`_: fix a regression to
process environment cleanup, caused by the change in v0.2.1 to run local
tasks with the correct environment.
* `#317 <https://github.com/dw/mitogen/issues/317>`_: respect the verbosity
setting when writing to to Ansible's ``log_path`` log file, if it is enabled.
Child log filtering was also incorrect, causing the master to needlessly wake
many times. This nets a 3.5% runtime improvement running against the local
machine.
Core Library
~~~~~~~~~~~~
* `#291 <https://github.com/dw/mitogen/issues/291>`_: the ``python_path``
paramater may specify an argument vector prefix rather than a single string
program path.
* `#303 <https://github.com/dw/mitogen/pull/303>`_: the ``doas`` become method
is now supported. Contributed by `Mike Walker
<https://github.com/napkindrawing>`_.
* `#307 <https://github.com/dw/mitogen/issues/307>`_: SSH login banner output
containing the word 'password' is no longer confused for a password prompt.
* Debug logs containing command lines are printed with the minimal quoting and
escaping required.
Thanks!
~~~~~~~
Mitogen would not be possible without the support of users. A huge thanks for
the bug reports and pull requests in this release contributed by
`Frances Albanese <https://github.com/falbanese>`_,
`Mark Janssen <https://github.com/sigio>`_,
`Ayaz Ahmed Khan <https://github.com/ayaz>`_,
`Colin McCarthy <https://github.com/colin-mccarthy>`_,
`Dan Quackenbush <https://github.com/danquack>`_,
`Alex Russu <https://github.com/alexrussu>`_,
`Josh Smift <https://github.com/jbscare>`_, and
`Mike Walker <https://github.com/napkindrawing>`_.
v0.2.1 (2018-07-10)
-------------------
Mitogen for Ansible
~~~~~~~~~~~~~~~~~~~
* `#297 <https://github.com/dw/mitogen/issues/297>`_: compatibility: local
actions set their working directory to that of their defining playbook, and
inherit a process environment as if they were executed as a subprocess of the
forked task worker.
v0.2.0 (2018-07-09)
-------------------
Mitogen 0.2.x is the inaugural feature-frozen branch eligible for fixes only,
except for problem areas listed as in-scope below. While stable from a
development perspective, it should still be considered "beta" at least for the
initial releases.
**In Scope**
* Python 3.x performance improvements
* Subprocess reaping improvements
* Major documentation improvements
* PyPI/packaging improvements
* Test suite improvements
* Replacement CI system to handle every supported OS
* Minor deviations from vanilla Ansible behaviour
* Ansible ``raw`` action support
The goal is a *tick/tock* model where even-numbered series are a maturation of
the previous unstable series, and unstable series are released on PyPI with
``--pre`` enabled. The API and user visible behaviour should remain unchanged
within a stable series.
Mitogen for Ansible
~~~~~~~~~~~~~~~~~~~
* Support for Ansible 2.3 - 2.5.x and any mixture of Python 2.6, 2.7 or 3.6 on
controller and target nodes.
* Drop-in support for many Ansible connection types.
* Preview of Connection Delegation feature.
* Built-in file transfer compatible with connection delegation.
**Known Issues**
* The ``raw`` action executes as a regular Mitogen connection, which requires
Python on the target, precluding its use for installing Python. This will be
addressed in a future 0.2 release. For now, simply mix Mitogen and vanilla
Ansible strategies in your playbook:
.. code-block:: yaml
- hosts: web-servers
strategy: linear
tasks:
- name: Install Python if necessary.
raw: test -e /usr/bin/python || apt install -y python-minimal
- hosts: web-servers
strategy: mitogen_linear
roles:
- nginx
- initech_app
- y2k_fix
* When running with ``-vvv``, log messages such as *mitogen: Router(Broker(0x7f5a48921590)): no route
for Message(..., 102, ...), my ID is ...* may be visible. These are due to a
minor race while initializing logging and can be ignored.
* Performance does not scale linearly with target count. This requires
significant additional work, as major bottlenecks exist in the surrounding
Ansible code. Performance-related bug reports for any scenario remain
welcome with open arms.
* Performance on Python 3 is significantly worse than on Python 2. While this
has not yet been investigated, at least some of the regression appears to be
part of the core library, and should therefore be straightforward to fix as
part of 0.2.x.
* *Module Replacer* style Ansible modules are not supported.
* Actions are single-threaded for each `(host, user account)` combination,
including actions that execute on the local machine. Playbooks may experience
slowdown compared to vanilla Ansible if they employ long-running
``local_action`` or ``delegate_to`` tasks delegating many target hosts to a
single machine and user account.
* Connection Delegation remains in preview and has bugs around how it infers
connections. Connection establishment will remain single-threaded for the 0.2
series, however connection inference bugs will be addressed in a future 0.2
release.
* Connection Delegation does not support automatic tunnelling of SSH-dependent
actions, such as the ``synchronize`` module. This will be addressed in the
0.3 series.
* Configurations will break that rely on the `hashbang argument splitting
behaviour <https://github.com/ansible/ansible/issues/15635>`_ of the
``ansible_python_interpreter`` setting, contrary to the Ansible
documentation. This will be addressed in a future 0.2 release.
Core Library
~~~~~~~~~~~~
* Synchronous connection establishment via OpenSSH, sudo, su, Docker, LXC and
FreeBSD Jails, local subprocesses and :func:`os.fork`. Parallel connection
setup is possible using multiple threads. Connections may be used from one or
many threads after establishment.
* UNIX masters and children, with Linux, MacOS, FreeBSD, NetBSD, OpenBSD and
Windows Subsystem for Linux explicitly supported.
* Automatic tests covering Python 2.6, 2.7 and 3.6 on Linux only.
**Known Issues**
* Serialization is still based on :mod:`pickle`. While there is high confidence
remote code execution is impossible in Mitogen's configuration, an untrusted
context may at least trigger disproportionately high memory usage injecting
small messages (*"billion laughs attack"*). Replacement is an important
future priority, but not critical for an initial release.
* Child processes are not reliably reaped, leading to a pileup of zombie
processes when a program makes many short-lived connections in a single
invocation. This does not impact Mitogen for Ansible, however it limits the
usefulness of the core library. A future 0.2 release will address it.
* Some races remain around :class:`mitogen.core.Broker <Broker>` destruction,
disconnection and corresponding file descriptor closure. These are only
problematic in situations where child process reaping is also problematic.
* The `fakessh` component does not shut down correctly and requires flow
control added to the design. While minimal fixes are possible, due to the
6 years ago
absence of flow control the original design is functionally incomplete.
* The multi-threaded :ref:`service` remains in a state of design flux and
should be considered obsolete, despite heavy use in Mitogen for Ansible. A
future replacement may be integrated more tightly with, or entirely replace
the RPC dispatcher on the main thread.
* Documentation is in a state of disrepair. This will be improved over the 0.2
series.