.. _changelog: Release Notes ============= .. raw:: html .. _known_issues: Known Issues ------------ Mitogen For Ansible ~~~~~~~~~~~~~~~~~~~ * The Ansible 2.7 `reboot `_ module may require a ``pre_reboot_delay`` on systemd hosts, as insufficient time exists for the reboot command's exit status to be reported before necessary processes are torn down. * On OS X when a SSH password is specified and the default connection type of ``smart`` is used, Ansible may select the Paramiko plug-in rather than Mitogen. If you specify a password on OS X, ensure ``connection: ssh`` appears in your playbook, ``ansible.cfg``, or as ``-c ssh`` on the command-line. * 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 `_ of the ``ansible_python_interpreter`` setting, contrary to the Ansible documentation. This will be addressed in a future 0.2 release. * 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 ~~~~~~~~~~~~ * 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 ` 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 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. v0.2.4 (2018-??-??) ------------------- Mitogen for Ansible ~~~~~~~~~~~~~~~~~~~ Enhancements ^^^^^^^^^^^^ * `#76 `_, `#351 `_, `#352 `_: disconnect propagation has improved, allowing Ansible to cancel waits for responses from abruptly disconnected targets. This ensures a task will gracefully fail rather than hang, for example on network failure or EC2 instance maintenance. * `#369 `_, `#407 `_: :meth:`Connection.reset` is implemented, allowing `meta: reset_connection `_ to shut down the remote interpreter as documented, and improving support for the `reboot `_ module. * `09aa27a6 `_: the ``mitogen_host_pinned`` strategy wraps the ``host_pinned`` strategy introduced in Ansible 2.7. * `#412 `_: to simplify diagnosing issues with connection configuration, Mitogen ships with a ``mitogen_get_stack`` action that is automatically added to the action plug-in path. See :ref:`mitogen-get-stack` for more information. * `#415 `_: the interface employed for in-process queues was changed from `kqueue `_ / `epoll `_ to `poll() `_, which requires no setup or teardown, yielding a 30% latency reduction for inter-thread communication and a 50% reduction in context switches. This will manifest as a runtime improvement in many-host runs. Fixes ^^^^^ * `#251 `_, `#359 `_, `#396 `_, `#401 `_, `#404 `_, `#412 `_, `#434 `_, `#436 `_, `#465 `_: connection delegation and ``delegate_to:`` handling suffered a major regression in 0.2.3. The 0.2.2 behaviour has been restored, and further work has been made to improve the compatibility of connection delegation's configuration building methods. * `#323 `_, `#333 `_: work around a Windows Subsystem for Linux bug that caused tracebacks to appear during shutdown. * `#334 `_: the SSH method tilde-expands private key paths using Ansible's logic. Previously the path was passed unmodified to SSH, which expanded it using :func:`pwd.getpwnam`. This differs from :func:`os.path.expanduser`, which uses the ``HOME`` environment variable if it is set, causing behaviour to diverge when Ansible was invoked across user accounts via ``sudo``. * `#364 `_: file transfers from controllers running Python 2.7.2 or earlier could be interrupted due to a forking bug in the :mod:`tempfile` module. * `#370 `_: the Ansible `reboot `_ module is supported. * `#373 `_: the LXC and LXD methods print a useful hint on failure, as no useful error is normally logged to the console by these tools. * `#374 `_, `#391 `_: file transfer and module execution from 2.x controllers to 3.x targets was broken due to a regression caused by refactoring, and compounded by `#426 `_. * `#400 `_: work around a threading bug in the AWX display callback when running with high verbosity setting. * `#409 `_: the setns method was silently broken due to missing tests. Basic coverage was added to prevent a recurrence. * `#409 `_: the LXC and LXD methods support ``mitogen_lxc_path`` and ``mitogen_lxc_attach_path`` variables to control the location of third pary utilities. * `#410 `_: the sudo method supports the SELinux ``--type`` and ``--role`` options. * `#420 `_: if a :class:`Connection` was constructed in the Ansible top-level process, for example while executing ``meta: reset_connection``, resources could become undesirably shared in subsequent children. * `#426 `_: an oversight while porting to Python 3 meant no automated 2->3 tests were running. A significant number of 2->3 bugs were fixed, mostly in the form of Unicode/bytes mismatches. * `#362 `_, `#435 `_: the previous fix for slow Python 2.x subprocess creation on Red Hat caused newly spawned children to have a reduced open files limit. A more intrusive fix has been added to directly address the problem without modifying the subprocess environment. * `#397 `_, `#454 `_: the previous approach to handling modern Ansible temporary file cleanup was too aggressive, and could trigger early finalization of Cython-based extension modules, leading to segmentation faults. Core Library ~~~~~~~~~~~~ * `#76 `_: routing records the destination context IDs ever received on each stream, and when disconnection occurs, propagates :data:`mitogen.core.DEL_ROUTE` messages towards every stream that ever communicated with the disappearing peer, rather than simply towards parents. Conversations between nodes anywhere in the tree receive :data:`mitogen.core.DEL_ROUTE` when either participant disconnects, allowing receivers to wake with :class:`mitogen.core.ChannelError`, even when one participant is not a parent of the other. * `#109 `_, `57504ba6 `_: newer Python 3 releases explicitly populate :data:`sys.meta_path` with importer internals, causing Mitogen to install itself at the end of the importer chain rather than the front. * `#310 `_: support has returned for trying to figure out the real source of non-module objects installed in :data:`sys.modules`, so they can be imported. This is needed to handle syntax sugar used by packages like :mod:`plumbum`. * `#349 `_: an incorrect format string could cause large stack traces when attempting to import built-in modules on Python 3. * `#387 `_, `#413 `_: dead messages include an optional reason in their body. This is used to cause :class:`mitogen.core.ChannelError` to report far more useful diagnostics at the point the error occurs that previously would have been buried in debug log output from an unrelated context. * `#408 `_: a variety of fixes were made to restore Python 2.4 compatibility. * `#399 `_, `#437 `_: ignore a :class:`DeprecationWarning` to avoid failure of the ``su`` method on Python 3.7. * `#405 `_: if an oversized message is rejected, and it has a ``reply_to`` set, a dead message is returned to the sender. This ensures function calls exceeding the configured maximum size crash rather than hang. * `#406 `_: :class:`mitogen.core.Broker` did not call :meth:`mitogen.core.Poller.close` during shutdown, leaking the underlying poller FD in masters and parents. * `#406 `_: connections could leak FDs when a child process failed to start. * `#288 `_, `#406 `_, `#417 `_: connections could leave FD wrapper objects that had not been closed lying around to be closed during garbage collection, causing reused FD numbers to be closed at random moments. * `#411 `_: the SSH method typed "``y``" rather than the requisite "``yes``" when `check_host_keys="accept"` was configured. This would lead to connection timeouts due to the hung response. * `#414 `_, `#425 `_: avoid deadlock of forked children by reinitializing the :mod:`mitogen.service` pool lock. * `#416 `_: around 1.4KiB of memory was leaked on every RPC, due to a list of strong references keeping alive any handler ever registered for disconnect notification. * `#418 `_: the :func:`mitogen.parent.iter_read` helper would leak poller FDs, because execution of its :keyword:`finally` block was delayed on Python 3. Now callers explicitly close the generator when finished. * `#422 `_: the fork method could fail to start if :data:`sys.stdout` was opened in block buffered mode, and buffered data was pending in the parent prior to fork. * `#438 `_: a descriptive error is logged when stream corruption is detected. * `#439 `_: descriptive errors are raised when attempting to invoke unsupported function types. * `#444 `_: messages regarding unforwardable extension module are no longer logged as errors. * `#445 `_: service pools unregister the :data:`mitogen.core.CALL_SERVICE` handle at shutdown, ensuring any outstanding messages are either processed by the pool as it shuts down, or have dead messages sent in reply to them, preventing peer contexts from hanging due to a forgotten buffered message. * `#446 `_: given thread A calling :meth:`mitogen.core.Receiver.close`, and thread B, C, and D sleeping in :meth:`mitogen.core.Receiver.get`, previously only one sleeping thread would be woken with :class:`mitogen.core.ChannelError` when the receiver was closed. Now all threads are woken per the docstring. * `#447 `_: duplicate attempts to invoke :meth:`mitogen.core.Router.add_handler` cause an error to be raised, ensuring accidental re-registration of service pools are reported correctly. * `#448 `_: the import hook implementation now raises :class:`ModuleNotFoundError` instead of :class:`ImportError` in Python 3.6 and above, to cope with an upcoming version of the :mod:`subprocess` module requiring this new subclass to be raised. * `#453 `_: the loggers used in children for standard IO redirection have propagation disabled, preventing accidental reconfiguration of the :mod:`logging` package in a child from setting up a feedback loop. * `#456 `_: a descriptive error is logged when :meth:`mitogen.core.Broker.defer` is called after the broker has shut down, preventing new messages being enqueued that will never be sent, and subsequently producing a program hang. * `#459 `_: the beginnings of a :meth:`mitogen.master.Router.get_stats` call has been added. The initial statistics cover the module loader only. * `#462 `_: Mitogen could fail to open a PTY on broken Linux systems due to a bad interaction between the glibc :func:`grantpt` function and an incorrectly mounted ``/dev/pts`` filesystem. Since correct group ownership is not required in most scenarios, when this problem is detected, the PTY is allocated and opened directly by the library. * `16ca111e `_: handle OpenSSH 7.5 permission denied prompts when ``~/.ssh/config`` rewrites are present. * `9ec360c2 `_: a new :meth:`mitogen.core.Broker.defer_sync` utility function is provided. * `f20e0bba `_: :meth:`mitogen.service.FileService.register_prefix` permits granting unprivileged access to whole filesystem subtrees, rather than single files at a time. * `8f85ee03 `_: :meth:`mitogen.core.Router.myself` returns a :class:`mitogen.core.Context` referring to the current process. * `824c7931 `_: exceptions raised by the import hook were updated to include probable reasons for a failure. * `57b652ed `_: a stray import meant an extra roundtrip and ~20KiB of data was wasted for any context that imported :mod:`mitogen.parent`. Thanks! ~~~~~~~ Mitogen would not be possible without the support of users. A huge thanks for bug reports, testing, features and fixes in this release contributed by `Andreas Krüger `_, `Anton Stroganov `_, `Berend De Schouwer `_, `Brian Candler `_, `dsgnr `_, `Duane Zamrok `_, `Eric Chang `_, `Gerben Meijer `_, `Guy Knights `_, `Jesse London `_, `Jiří Vávra `_, `Johan Beisser `_, `Jonathan Rosser `_, `Josh Smift `_, `Mehdi `_, `Michael DeHaan `_, `Michal Medvecky `_, `Mohammed Naser `_, `Peter V. Saveliev `_, `Pieter Avonts `_, `Ross Williams `_, `Sergey `_, `Stéphane `_, `Strahinja Kustudic `_, `Tom Parker-Shemilt `_, `Younès HAFRI `_, `@myssa91 `_, `@syntonym `_, `@trim777 `_, `@whky `_, and `@yodatak `_. v0.2.3 (2018-10-23) ------------------- Mitogen for Ansible ~~~~~~~~~~~~~~~~~~~ Enhancements ^^^^^^^^^^^^ * `#315 `_, `#392 `_: Ansible 2.6 and 2.7 are supported. * `#321 `_, `#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 `_, `aws_s3 `_, `copy `_, `patch `_, `script `_, `template `_, `unarchive `_, `uri `_). See :ref:`ansible_tempfiles` for a complete description. * `#376 `_, `#377 `_: the ``kubectl`` connection type is now supported. Contributed by Yannig Perré. * `084c0ac0 `_: avoid a roundtrip in `copy `_ and `template `_ due to an unfortunate default. * `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 `_: To avoid a scaling limitation, a PTY is no longer allocated for an SSH connection unless the configuration specifies a password. * `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 `_: threads are cooperatively scheduled, minimizing `GIL `_ 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 `_ 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 `_, `#340 `_: Connection Delegation could establish connections to the wrong target when ``delegate_to:`` is present. * `#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 `_: plays with a `custom module_utils `_ would fail due to fallout from the Python 3 port and related tests being disabled. * `#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 `_: support a new :func:`sys.excepthook`-based module exit mechanism added in Ansible 2.6. * `#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 `_: the sudo ``--login`` option is supported. * `#344 `_: connections no longer fail when the controller's login username contains slashes. * `#345 `_: the ``IdentitiesOnly yes`` option is no longer supplied to OpenSSH by default, better matching Ansible's behaviour. * `#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 `_: 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 `_: 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 `_, `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 `_: fix a long-standing minor race relating to the logging framework, where *no route for Message..* would frequently appear during startup. * `#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 `_: 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 `_: the LXD connection method was erroneously executing LXC Classic commands. * `#345 `_: the SSH connection method allows optionally disabling ``IdentitiesOnly yes``. * `#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 `_, `#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 `_: the LXC connection method uses a more compatible method to establish an non-interactive session. Contributed by Brian Candler. * `af2ded66 `_: add :func:`mitogen.fork.on_fork` to allow non-Mitogen managed process forks to clean up Mitogen resources in the child. * `d6784242 `_: the setns method always resets ``HOME``, ``SHELL``, ``LOGNAME`` and ``USER`` environment variables to an account in the target container, defaulting to ``root``. * `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, testing, features and fixes in this release contributed by `Alex Russu `_, `Alex Willmer `_, `atoom `_, `Berend De Schouwer `_, `Brian Candler `_, `Dan Quackenbush `_, `dsgnr `_, `Jesse London `_, `John McGrath `_, `Jonathan Rosser `_, `Josh Smift `_, `Luca Nunzi `_, `Orion Poplawski `_, `Peter V. Saveliev `_, `Pierre-Henry Muller `_, `Pierre-Louis Bonicoli `_, `Prateek Jain `_, `RedheatWei `_, `Rick Box `_, `nikitakazantsev12 `_, `Tawana Musewe `_, `Timo Beckers `_, and `Yannig Perré `_. v0.2.2 (2018-07-26) ------------------- Mitogen for Ansible ~~~~~~~~~~~~~~~~~~~ * `#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 `_: 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 `_: variables like ``$HOME`` in the ``remote_tmp`` setting are evaluated correctly. * `#303 `_: the :ref:`doas` become method is supported. Contributed by `Mike Walker `_. * `#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 `_: 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 `_: the ``python_path`` parameter may specify an argument vector prefix rather than a string program path. * `#300 `_: the broker could crash on OS X during shutdown due to scheduled `kqueue `_ 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 `_: the :ref:`doas` become method is now supported. Contributed by `Mike Walker `_. * `#307 `_: SSH login banner output containing the word 'password' is no longer confused for a password prompt. * `#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 `_: 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 `_: 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 `_, `Andy Freeland `_, `Ayaz Ahmed Khan `_, `Colin McCarthy `_, `Dan Quackenbush `_, `Duane Zamrok `_, `Gonzalo Servat `_, `Guy Knights `_, `Josh Smift `_, `Mark Janssen `_, `Mike Walker `_, `Orion Poplawski `_, `falbanese `_, `Tawana Musewe `_, and `Zach Swanson `_. v0.2.1 (2018-07-10) ------------------- Mitogen for Ansible ~~~~~~~~~~~~~~~~~~~ * `#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. 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.