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mitogen/docs/changelog.rst

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.. _changelog:
Release Notes
=============
.. raw:: html
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div#release-notes h2 {
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v0.2.4 (2018-??-??)
------------------
Mitogen for Ansible
~~~~~~~~~~~~~~~~~~~
Enhancements
^^^^^^^^^^^^
Fixes
^^^^^
Core Library
~~~~~~~~~~~~
* `#76 <https://github.com/dw/mitogen/issues/76>`_: routing maintains the set
of destination context ID ever received on each stream, and when
disconnection occurs, propagates ``DEL_ROUTE`` messages downwards towards
every stream that ever communicated with a disappearing peer, rather than
simply toward parents.
Conversations between nodes in any level of the connection tree should
correctly receive ``DEL_ROUTE`` messages when a participant disconnects,
allowing receivers to be woken with :class:`mitogen.core.ChannelError` to
signal the connection has broken, even when one participant is not a parent
of the other.
v0.2.3 (2018-10-23)
-------------------
Mitogen for Ansible
~~~~~~~~~~~~~~~~~~~
Enhancements
^^^^^^^^^^^^
* `#315 <https://github.com/dw/mitogen/pull/315>`_,
`#392 <https://github.com/dw/mitogen/issues/392>`_: Ansible 2.6 and 2.7 are
supported.
* `#321 <https://github.com/dw/mitogen/issues/321>`_,
`#336 <https://github.com/dw/mitogen/issues/336>`_: temporary file handling
was simplified, undoing earlier damage caused by compatibility fixes,
improving 2.6 compatibility, and avoiding two network roundtrips for every
related action
(`assemble <http://docs.ansible.com/ansible/latest/modules/assemble_module.html>`_,
`aws_s3 <http://docs.ansible.com/ansible/latest/modules/aws_s3_module.html>`_,
`copy <http://docs.ansible.com/ansible/latest/modules/copy_module.html>`_,
`patch <http://docs.ansible.com/ansible/latest/modules/patch_module.html>`_,
`script <http://docs.ansible.com/ansible/latest/modules/script_module.html>`_,
`template <http://docs.ansible.com/ansible/latest/modules/template_module.html>`_,
`unarchive <http://docs.ansible.com/ansible/latest/modules/unarchive_module.html>`_,
`uri <http://docs.ansible.com/ansible/latest/modules/uri_module.html>`_). See
:ref:`ansible_tempfiles` for a complete description.
* `#376 <https://github.com/dw/mitogen/pull/376>`_,
`#377 <https://github.com/dw/mitogen/pull/377>`_: the ``kubectl`` connection
type is now supported. Contributed by Yannig Perré.
* `084c0ac0 <https://github.com/dw/mitogen/commit/084c0ac0>`_: avoid a
roundtrip in
`copy <http://docs.ansible.com/ansible/latest/modules/copy_module.html>`_ and
`template <http://docs.ansible.com/ansible/latest/modules/template_module.html>`_
due to an unfortunate default.
* `7458dfae <https://github.com/dw/mitogen/commit/7458dfae>`_: avoid a
roundtrip when transferring files smaller than 124KiB. Copy and template
actions are now 2-RTT, reducing runtime for a 20-iteration template loop over
a 250 ms link from 30 seconds to 10 seconds compared to v0.2.2, down from 120
seconds compared to vanilla.
* `#337 <https://github.com/dw/mitogen/issues/337>`_: To avoid a scaling
limitation, a PTY is no longer allocated for an SSH connection unless the
configuration specifies a password.
* `d62e6e2a <https://github.com/dw/mitogen/commit/d62e6e2a>`_: many-target
runs executed the dependency scanner redundantly due to missing
synchronization, wasting significant runtime in the connection multiplexer.
In one case work was reduced by 95%, which may manifest as faster runs.
* `5189408e <https://github.com/dw/mitogen/commit/5189408e>`_: threads are
cooperatively scheduled, minimizing `GIL
<https://en.wikipedia.org/wiki/Global_interpreter_lock>`_ contention, and
reducing context switching by around 90%. This manifests as an overall
improvement, but is easily noticeable on short many-target runs, where
startup overhead dominates runtime.
* The `faulthandler <https://faulthandler.readthedocs.io/>`_ module is
automatically activated if it is installed, simplifying debugging of hangs.
See :ref:`diagnosing-hangs` for details.
* The ``MITOGEN_DUMP_THREAD_STACKS`` environment variable's value now indicates
the number of seconds between stack dumps. See :ref:`diagnosing-hangs` for
details.
Fixes
^^^^^
* `#251 <https://github.com/dw/mitogen/issues/251>`_,
`#340 <https://github.com/dw/mitogen/issues/340>`_: Connection Delegation
could establish connections to the wrong target when ``delegate_to:`` is
present.
* `#291 <https://github.com/dw/mitogen/issues/291>`_: when Mitogen had
previously been installed using ``pip`` or ``setuptools``, the globally
installed version could conflict with a newer version bundled with an
extension that had been installed using the documented steps. Now the bundled
library always overrides over any system-installed copy.
* `#324 <https://github.com/dw/mitogen/issues/324>`_: plays with a
`custom module_utils <https://docs.ansible.com/ansible/latest/reference_appendices/config.html#default-module-utils-path>`_
would fail due to fallout from the Python 3 port and related tests being
disabled.
* `#331 <https://github.com/dw/mitogen/issues/331>`_: the connection
multiplexer subprocess always exits before the main Ansible process, ensuring
logs generated by it do not overwrite the user's prompt when ``-vvv`` is
enabled.
* `#332 <https://github.com/dw/mitogen/issues/332>`_: support a new
:func:`sys.excepthook`-based module exit mechanism added in Ansible 2.6.
* `#338 <https://github.com/dw/mitogen/issues/338>`_: compatibility: changes to
``/etc/environment`` and ``~/.pam_environment`` made by a task are reflected
in the runtime environment of subsequent tasks. See
:ref:`ansible_process_env` for a complete description.
* `#343 <https://github.com/dw/mitogen/issues/343>`_: the sudo ``--login``
option is supported.
* `#344 <https://github.com/dw/mitogen/issues/344>`_: connections no longer
fail when the controller's login username contains slashes.
* `#345 <https://github.com/dw/mitogen/issues/345>`_: the ``IdentitiesOnly
yes`` option is no longer supplied to OpenSSH by default, better matching
Ansible's behaviour.
* `#355 <https://github.com/dw/mitogen/issues/355>`_: tasks configured to run
in an isolated forked subprocess were forked from the wrong parent context.
This meant built-in modules overridden via a custom ``module_utils`` search
path may not have had any effect.
* `#362 <https://github.com/dw/mitogen/issues/362>`_: to work around a slow
algorithm in the :mod:`subprocess` module, the maximum number of open files
in processes running on the target is capped to 512, reducing the work
required to start a subprocess by >2000x in default CentOS configurations.
* `#397 <https://github.com/dw/mitogen/issues/397>`_: recent Mitogen master
versions could fail to clean up temporary directories in a number of
circumstances, and newer Ansibles moved to using :mod:`atexit` to effect
temporary directory cleanup in some circumstances.
* `b9112a9c <https://github.com/dw/mitogen/commit/b9112a9c>`_,
`2c287801 <https://github.com/dw/mitogen/commit/2c287801>`_: OpenSSH 7.5
permission denied prompts are now recognized. Contributed by Alex Willmer.
* A missing check caused an exception traceback to appear when using the
``ansible`` command-line tool with a missing or misspelled module name.
* Ansible since >=2.7 began importing :mod:`__main__` from
:mod:`ansible.module_utils.basic`, causing an error during execution, due to
the controller being configured to refuse network imports outside the
``ansible.*`` namespace. Update the target implementation to construct a stub
:mod:`__main__` module to satisfy the otherwise seemingly vestigial import.
Core Library
~~~~~~~~~~~~
* A new :class:`mitogen.parent.CallChain` class abstracts safe pipelining of
related function calls to a target context, cancelling the chain if an
exception occurs.
* `#305 <https://github.com/dw/mitogen/issues/305>`_: fix a long-standing minor
race relating to the logging framework, where *no route for Message..*
would frequently appear during startup.
* `#313 <https://github.com/dw/mitogen/issues/313>`_:
:meth:`mitogen.parent.Context.call` was documented as capable of accepting
static methods. While possible on Python 2.x the result is ugly, and in every
case it should be trivial to replace with a classmethod. The documentation
was fixed.
* `#337 <https://github.com/dw/mitogen/issues/337>`_: to avoid a scaling
limitation, a PTY is no longer allocated for each OpenSSH client if it can be
avoided. PTYs are only allocated if a password is supplied, or when
`host_key_checking=accept`. This is since Linux has a default of 4096 PTYs
(``kernel.pty.max``), while OS X has a default of 127 and an absolute maximum
of 999 (``kern.tty.ptmx_max``).
* `#339 <https://github.com/dw/mitogen/issues/339>`_: the LXD connection method
was erroneously executing LXC Classic commands.
* `#345 <https://github.com/dw/mitogen/issues/345>`_: the SSH connection method
allows optionally disabling ``IdentitiesOnly yes``.
* `#356 <https://github.com/dw/mitogen/issues/356>`_: if the master Python
process does not have :data:`sys.executable` set, the default Python
interpreter used for new children on the local machine defaults to
``"/usr/bin/python"``.
* `#366 <https://github.com/dw/mitogen/issues/366>`_,
`#380 <https://github.com/dw/mitogen/issues/380>`_: attempts by children to
import :mod:`__main__` where the main program module lacks an execution guard
are refused, and an error is logged. This prevents a common and highly
confusing error when prototyping new scripts.
* `#371 <https://github.com/dw/mitogen/pull/371>`_: the LXC connection method
uses a more compatible method to establish an non-interactive session.
Contributed by Brian Candler.
* `af2ded66 <https://github.com/dw/mitogen/commit/af2ded66>`_: add
:func:`mitogen.fork.on_fork` to allow non-Mitogen managed process forks to
clean up Mitogen resources in the child.
* `d6784242 <https://github.com/dw/mitogen/commit/d6784242>`_: the setns method
always resets ``HOME``, ``SHELL``, ``LOGNAME`` and ``USER`` environment
variables to an account in the target container, defaulting to ``root``.
* `830966bf <https://github.com/dw/mitogen/commit/830966bf>`_: the UNIX
listener no longer crashes if the peer process disappears in the middle of
connection setup.
Thanks!
~~~~~~~
Mitogen would not be possible without the support of users. A huge thanks for
bug reports, features and fixes in this release contributed by
`Alex Russu <https://github.com/alexrussu>`_,
`Alex Willmer <https://github.com/moreati>`_,
`atoom <https://github.com/atoom>`_,
`Berend De Schouwer <https://github.com/berenddeschouwer>`_,
`Brian Candler <https://github.com/candlerb>`_,
`Dan Quackenbush <https://github.com/danquack>`_,
`dsgnr <https://github.com/dsgnr>`_,
`Jesse London <https://github.com/jesteria>`_,
`John McGrath <https://github.com/jmcgrath207>`_,
`Jonathan Rosser <https://github.com/jrosser>`_,
`Josh Smift <https://github.com/jbscare>`_,
`Luca Nunzi <https://github.com/0xlc>`_,
`Orion Poplawski <https://github.com/opoplawski>`_,
`Peter V. Saveliev <https://github.com/svinota>`_,
`Pierre-Henry Muller <https://github.com/pierrehenrymuller>`_,
`Pierre-Louis Bonicoli <https://github.com/jesteria>`_,
`Prateek Jain <https://github.com/prateekj201>`_,
`RedheatWei <https://github.com/RedheatWei>`_,
`Rick Box <https://github.com/boxrick>`_,
`nikitakazantsev12 <https://github.com/nikitakazantsev12>`_,
`Tawana Musewe <https://github.com/tbtmuse>`_,
`Timo Beckers <https://github.com/ti-mo>`_, and
`Yannig Perré <https://github.com/yannig>`_.
v0.2.2 (2018-07-26)
-------------------
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.
* `#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 :ref:`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 Ansible's ``log_path``, 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.
* The ``mitogen_ssh_debug_level`` variable is supported, permitting SSH debug
output to be included in Mitogen's ``-vvv`` output when both are specified.
Core Library
~~~~~~~~~~~~
* `#291 <https://github.com/dw/mitogen/issues/291>`_: the ``python_path``
parameter may specify an argument vector prefix rather than a string program
path.
* `#300 <https://github.com/dw/mitogen/issues/300>`_: the broker could crash on
OS X during shutdown due to scheduled `kqueue
<https://www.freebsd.org/cgi/man.cgi?query=kevent>`_ filter changes for
descriptors that were closed before the IO loop resumes. As a temporary
workaround, kqueue's bulk change feature is not used.
* `#303 <https://github.com/dw/mitogen/pull/303>`_: the :ref:`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.
* `#319 <https://github.com/dw/mitogen/issues/319>`_: SSH connections would
fail immediately on Windows Subsystem for Linux, due to use of `TCSAFLUSH`
with :func:`termios.tcsetattr`. The flag is omitted if WSL is detected.
* `#320 <https://github.com/dw/mitogen/issues/320>`_: The OS X poller
could spuriously wake up due to ignoring an error bit set on events returned
by the kernel, manifesting as a failure to read from an unrelated descriptor.
* `#342 <https://github.com/dw/mitogen/issues/342>`_: The ``network_cli``
connection type would fail due to a missing internal SSH plugin method.
* Standard IO forwarding accidentally configured the replacement ``stdout`` and
``stderr`` write descriptors as non-blocking, causing subprocesses that
generate more output than kernel buffer space existed to throw errors. The
write ends are now configured as blocking.
* When :func:`mitogen.core.enable_profiling` is active, :mod:`mitogen.service`
threads are profiled just like other threads.
* The ``ssh_debug_level`` parameter is supported, permitting SSH debug output
to be redirected to a Mitogen logger when specified.
* 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
`Alex Russu <https://github.com/alexrussu>`_,
`Andy Freeland <https://github.com/rouge8>`_,
`Ayaz Ahmed Khan <https://github.com/ayaz>`_,
`Colin McCarthy <https://github.com/colin-mccarthy>`_,
`Dan Quackenbush <https://github.com/danquack>`_,
`Duane Zamrok <https://github.com/dewthefifth>`_,
`Gonzalo Servat <https://github.com/gservat>`_,
`Guy Knights <https://github.com/knightsg>`_,
`Josh Smift <https://github.com/jbscare>`_,
`Mark Janssen <https://github.com/sigio>`_,
`Mike Walker <https://github.com/napkindrawing>`_,
`Orion Poplawski <https://github.com/opoplawski>`_,
`falbanese <https://github.com/falbanese>`_,
`Tawana Musewe <https://github.com/tbtmuse>`_, and
`Zach Swanson <https://github.com/zswanson>`_.
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 - 2.7.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 will be printed to the console
*after* the Ansible run completes, as connection multiplexer shutdown only
begins after Ansible exits. This is due to a lack of suitable shutdown hook
in Ansible, and is fairly harmless, albeit cosmetically annoying. A future
release may include a solution.
.. * 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.
* The Ansible 2.7 ``reboot`` module is not yet supported.
* 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.
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.