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mitogen/docs/api.rst

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API Reference
*************
.. toctree::
:hidden:
signals
Package Layout
==============
mitogen Package
---------------
.. automodule:: mitogen
.. autodata:: mitogen.__version__
.. autodata:: mitogen.is_master
.. autodata:: mitogen.context_id
.. autodata:: mitogen.parent_id
.. autodata:: mitogen.parent_ids
.. autofunction:: mitogen.main
mitogen.core
------------
.. module:: mitogen.core
This module implements most package functionality, but remains separate from
non-essential code in order to reduce its size, since it is also serves as the
bootstrap implementation sent to every new slave context.
.. currentmodule:: mitogen.core
.. decorator:: takes_econtext
Decorator that marks a function or class method to automatically receive a
kwarg named `econtext`, referencing the
:py:class:`mitogen.core.ExternalContext` active in the context in which the
function is being invoked in. The decorator is only meaningful when the
function is invoked via :py:data:`CALL_FUNCTION
<mitogen.core.CALL_FUNCTION>`.
When the function is invoked directly, `econtext` must still be passed to
it explicitly.
.. currentmodule:: mitogen.core
.. decorator:: takes_router
Decorator that marks a function or class method to automatically receive a
kwarg named `router`, referencing the :py:class:`mitogen.core.Router`
active in the context in which the function is being invoked in. The
decorator is only meaningful when the function is invoked via
:py:data:`CALL_FUNCTION <mitogen.core.CALL_FUNCTION>`.
When the function is invoked directly, `router` must still be passed to it
explicitly.
mitogen.master
--------------
.. module:: mitogen.master
This module implements functionality required by master processes, such as
starting new contexts via SSH. Its size is also restricted, since it must
be sent to any context that will be used to establish additional child
contexts.
mitogen.fakessh
---------------
.. module:: mitogen.fakessh
fakessh is a stream implementation that starts a local subprocess with its
environment modified such that ``PATH`` searches for `ssh` return an mitogen
implementation of the SSH command. When invoked, this tool arranges for the
command line supplied by the calling program to be executed in a context
already established by the master process, reusing the master's (possibly
proxied) connection to that context.
This allows tools like `rsync` and `scp` to transparently reuse the connections
and tunnels already established by the host program to connect to a target
machine, without wasteful redundant SSH connection setup, 3-way handshakes, or
firewall hopping configurations, and enables these tools to be used in
impossible scenarios, such as over `sudo` with ``requiretty`` enabled.
The fake `ssh` command source is written to a temporary file on disk, and
consists of a copy of the :py:mod:`mitogen.core` source code (just like any
other child context), with a line appended to cause it to connect back to the
host process over an FD it inherits. As there is no reliance on an existing
filesystem file, it is possible for child contexts to use fakessh.
As a consequence of connecting back through an inherited FD, only one SSH
invocation is possible, which is fine for tools like `rsync`, however in future
this restriction will be lifted.
Sequence:
1. ``fakessh`` Context and Stream created by parent context. The stream's
buffer has a :py:func:`_fakessh_main` :py:data:`CALL_FUNCTION
<mitogen.core.CALL_FUNCTION>` enqueued.
2. Target program (`rsync/scp/sftp`) invoked, which internally executes
`ssh` from ``PATH``.
3. :py:mod:`mitogen.core` bootstrap begins, recovers the stream FD
inherited via the target program, established itself as the fakessh
context.
4. :py:func:`_fakessh_main` :py:data:`CALL_FUNCTION
<mitogen.core.CALL_FUNCTION>` is read by fakessh context,
a. sets up :py:class:`IoPump` for stdio, registers
stdin_handle for local context.
b. Enqueues :py:data:`CALL_FUNCTION <mitogen.core.CALL_FUNCTION>` for
:py:func:`_start_slave` invoked in target context,
i. the program from the `ssh` command line is started
ii. sets up :py:class:`IoPump` for `ssh` command line process's
stdio pipes
iii. returns `(control_handle, stdin_handle)` to
:py:func:`_fakessh_main`
5. :py:func:`_fakessh_main` receives control/stdin handles from from
:py:func:`_start_slave`,
a. registers remote's stdin_handle with local :py:class:`IoPump`.
b. sends `("start", local_stdin_handle)` to remote's control_handle
c. registers local :py:class:`IoPump` with
:py:class:`mitogen.core.Broker`.
d. loops waiting for `local stdout closed && remote stdout closed`
6. :py:func:`_start_slave` control channel receives `("start", stdin_handle)`,
a. registers remote's stdin_handle with local :py:class:`IoPump`
b. registers local :py:class:`IoPump` with
:py:class:`mitogen.core.Broker`.
c. loops waiting for `local stdout closed && remote stdout closed`
.. currentmodule:: mitogen.fakessh
.. function:: run (dest, router, args, daedline=None, econtext=None)
Run the command specified by the argument vector `args` such that ``PATH``
searches for SSH by the command will cause its attempt to use SSH to
execute a remote program to be redirected to use mitogen to execute that
program using the context `dest` instead.
:param mitogen.core.Context dest:
The destination context to execute the SSH command line in.
:param mitogen.core.Router router:
:param list[str] args:
Command line arguments for local program, e.g.
``['rsync', '/tmp', 'remote:/tmp']``
:returns:
Exit status of the child process.
Message Class
=============
.. currentmodule:: mitogen.core
.. class:: Message
.. attribute:: router
The :py:class:`mitogen.core.Router` responsible for routing the
message. This is :py:data:`None` for locally originated messages.
.. attribute:: receiver
The :py:class:`mitogen.core.Receiver` over which the message was last
received. Part of the :py:class:`mitogen.select.Select` interface.
Defaults to :py:data:`None`.
.. attribute:: dst_id
.. attribute:: src_id
.. attribute:: auth_id
.. attribute:: handle
.. attribute:: reply_to
.. attribute:: data
.. attribute:: is_dead
:data:`True` if :attr:`reply_to` is set to the magic value
:data:`mitogen.core.IS_DEAD`, indicating the sender considers the
channel dead.
.. py:method:: __init__ (\**kwargs)
Construct a message from from the supplied `kwargs`. :py:attr:`src_id`
and :py:attr:`auth_id` are always set to :py:data:`mitogen.context_id`.
.. py:classmethod:: pickled (obj, \**kwargs)
Construct a pickled message, setting :py:attr:`data` to the
serialization of `obj`, and setting remaining fields using `kwargs`.
:returns:
The new message.
.. method:: unpickle (throw=True)
Unpickle :py:attr:`data`, optionally raising any exceptions present.
:param bool throw:
If :py:data:`True`, raise exceptions, otherwise it is the caller's
responsibility.
:raises mitogen.core.CallError:
The serialized data contained CallError exception.
:raises mitogen.core.ChannelError:
The `is_dead` field was set.
.. method:: reply (obj, router=None, \**kwargs)
Compose a reply to this message and send it using :py:attr:`router`, or
`router` is :py:attr:`router` is :data:`None`.
:param obj:
Either a :class:`Message`, or an object to be serialized in order
to construct a new message.
:param router:
Optional router to use if :attr:`router` is :data:`None`.
:param kwargs:
Optional keyword parameters overriding message fields in the reply.
Router Class
============
.. currentmodule:: mitogen.core
.. class:: Router
Route messages between parent and child contexts, and invoke handlers
defined on our parent context. :py:meth:`Router.route() <route>` straddles
the :py:class:`Broker <mitogen.core.Broker>` and user threads, it is safe
to call anywhere.
**Note:** This is the somewhat limited core version of the Router class
used by child contexts. The master subclass is documented below this one.
.. attribute:: unidirectional
When :data:`True`, permit children to only communicate with the current
context or a parent of the current context. Routing between siblings or
children of parents is prohibited, ensuring no communication is
possible between intentionally partitioned networks, such as when a
program simultaneously manipulates hosts spread across a corporate and
a production network, or production networks that are otherwise
air-gapped.
Sending a prohibited message causes an error to be logged and a dead
message to be sent in reply to the errant message, if that message has
``reply_to`` set.
The value of :data:`unidirectional` becomes the default for the
:meth:`local() <mitogen.master.Router.local>` `unidirectional`
parameter.
.. method:: stream_by_id (dst_id)
Return the :py:class:`mitogen.core.Stream` that should be used to
communicate with `dst_id`. If a specific route for `dst_id` is not
known, a reference to the parent context's stream is returned.
.. method:: add_route (target_id, via_id)
Arrange for messages whose `dst_id` is `target_id` to be forwarded on
the directly connected stream for `via_id`. This method is called
automatically in response to ``ADD_ROUTE`` messages, but remains public
for now while the design has not yet settled, and situations may arise
where routing is not fully automatic.
.. method:: register (context, stream)
Register a new context and its associated stream, and add the stream's
receive side to the I/O multiplexer. This This method remains public
for now while hte design has not yet settled.
.. method:: add_handler (fn, handle=None, persist=True, respondent=None, policy=None)
Invoke `fn(msg)` for each Message sent to `handle` from this context.
Unregister after one invocation if `persist` is ``False``. If `handle`
is ``None``, a new handle is allocated and returned.
:param int handle:
If not ``None``, an explicit handle to register, usually one of the
``mitogen.core.*`` constants. If unspecified, a new unused handle
will be allocated.
:param bool persist:
If ``False``, the handler will be unregistered after a single
message has been received.
:param mitogen.core.Context respondent:
Context that messages to this handle are expected to be sent from.
If specified, arranges for a dead message to be delivered to `fn`
when disconnection of the context is detected.
In future `respondent` will likely also be used to prevent other
contexts from sending messages to the handle.
:param function policy:
Function invoked as `policy(msg, stream)` where `msg` is a
:py:class:`mitogen.core.Message` about to be delivered, and
`stream` is the :py:class:`mitogen.core.Stream` on which it was
received. The function must return :py:data:`True`, otherwise an
error is logged and delivery is refused.
Two built-in policy functions exist:
* :py:func:`mitogen.core.has_parent_authority`: requires the
message arrived from a parent context, or a context acting with a
parent context's authority (``auth_id``).
* :py:func:`mitogen.parent.is_immediate_child`: requires the
message arrived from an immediately connected child, for use in
messaging patterns where either something becomes buggy or
insecure by permitting indirect upstream communication.
In case of refusal, and the message's ``reply_to`` field is
nonzero, a :py:class:`mitogen.core.CallError` is delivered to the
sender indicating refusal occurred.
:return:
`handle`, or if `handle` was ``None``, the newly allocated handle.
.. method:: del_handler (handle)
Remove the handle registered for `handle`
:raises KeyError:
The handle wasn't registered.
.. method:: _async_route(msg, stream=None)
Arrange for `msg` to be forwarded towards its destination. If its
destination is the local context, then arrange for it to be dispatched
using the local handlers.
This is a lower overhead version of :py:meth:`route` that may only be
called from the I/O multiplexer thread.
:param mitogen.core.Stream stream:
If not ``None``, a reference to the stream the message arrived on.
Used for performing source route verification, to ensure sensitive
messages such as ``CALL_FUNCTION`` arrive only from trusted
contexts.
.. method:: route(msg)
Arrange for the :py:class:`Message` `msg` to be delivered to its
destination using any relevant downstream context, or if none is found,
by forwarding the message upstream towards the master context. If `msg`
is destined for the local context, it is dispatched using the handles
registered with :py:meth:`add_handler`.
This may be called from any thread.
.. currentmodule:: mitogen.master
.. class:: Router (broker=None)
Extend :py:class:`mitogen.core.Router` with functionality useful to
masters, and child contexts who later become masters. Currently when this
class is required, the target context's router is upgraded at runtime.
.. note::
You may construct as many routers as desired, and use the same broker
for multiple routers, however usually only one broker and router need
exist. Multiple routers may be useful when dealing with separate trust
domains, for example, manipulating infrastructure belonging to separate
customers or projects.
:param mitogen.master.Broker broker:
:py:class:`Broker` instance to use. If not specified, a private
:py:class:`Broker` is created.
.. attribute:: profiling
When :data:`True`, cause the broker thread and any subsequent broker
and main threads existing in any child to write
``/tmp/mitogen.stats.<pid>.<thread_name>.log`` containing a
:py:mod:`cProfile` dump on graceful exit. Must be set prior to
construction of any :py:class:`Broker`, e.g. via:
.. code::
mitogen.master.Router.profiling = True
.. method:: enable_debug
Cause this context and any descendant child contexts to write debug
logs to /tmp/mitogen.<pid>.log.
.. method:: allocate_id
Arrange for a unique context ID to be allocated and associated with a
route leading to the active context. In masters, the ID is generated
directly, in children it is forwarded to the master via an
``ALLOCATE_ID`` message that causes the master to emit matching
``ADD_ROUTE`` messages prior to replying.
.. method:: context_by_id (context_id, via_id=None)
Messy factory/lookup function to find a context by its ID, or construct
it. In future this will be replaced by a much more sensible interface.
.. _context-factories:
**Context Factories**
.. method:: fork (on_fork=None, on_start=None, debug=False, profiling=False, via=None)
Construct a context on the local machine by forking the current
process. The forked child receives a new identity, sets up a new broker
and router, and responds to function calls identically to children
created using other methods.
For long-lived processes, :py:meth:`local` is always better as it
guarantees a pristine interpreter state that inherited little from the
parent. Forking should only be used in performance-sensitive scenarios
where short-lived children must be spawned to isolate potentially buggy
code, and only after accounting for all the bad things possible as a
result of, at a minimum:
* Files open in the parent remaining open in the child,
causing the lifetime of the underlying object to be extended
indefinitely.
* From the perspective of external components, this is observable
in the form of pipes and sockets that are never closed, which may
break anything relying on closure to signal protocol termination.
* Descriptors that reference temporary files will not have their disk
space reclaimed until the child exits.
* Third party package state, such as urllib3's HTTP connection pool,
attempting to write to file descriptors shared with the parent,
causing random failures in both parent and child.
* UNIX signal handlers installed in the parent process remaining active
in the child, despite associated resources, such as service threads,
child processes, resource usage counters or process timers becoming
absent or reset in the child.
* Library code that makes assumptions about the process ID remaining
unchanged, for example to implement inter-process locking, or to
generate file names.
* Anonymous ``MAP_PRIVATE`` memory mappings whose storage requirement
doubles as either parent or child dirties their pages.
* File-backed memory mappings that cannot have their space freed on
disk due to the mapping living on in the child.
* Difficult to diagnose memory usage and latency spikes due to object
graphs becoming unreferenced in either parent or child, causing
immediate copy-on-write to large portions of the process heap.
* Locks held in the parent causing random deadlocks in the child, such
as when another thread emits a log entry via the :py:mod:`logging`
package concurrent to another thread calling :py:meth:`fork`.
* Objects existing in Thread-Local Storage of every non-:py:meth:`fork`
thread becoming permanently inaccessible, and never having their
object destructors called, including TLS usage by native extension
code, triggering many new variants of all the issues above.
* Pseudo-Random Number Generator state that is easily observable by
network peers to be duplicate, violating requirements of
cryptographic protocols through one-time state reuse. In the worst
case, children continually reuse the same state due to repeatedly
forking from a static parent.
:py:meth:`fork` cleans up Mitogen-internal objects, in addition to
locks held by the :py:mod:`logging` package, reseeds
:py:func:`random.random`, and the OpenSSL PRNG via
:py:func:`ssl.RAND_add`, but only if the :py:mod:`ssl` module is
already loaded. You must arrange for your program's state, including
any third party packages in use, to be cleaned up by specifying an
`on_fork` function.
The associated stream implementation is
:py:class:`mitogen.fork.Stream`.
:param function on_fork:
Function invoked as `on_fork()` from within the child process. This
permits supplying a program-specific cleanup function to break
locks and close file descriptors belonging to the parent from
within the child.
:param function on_start:
Invoked as `on_start(econtext)` from within the child process after
it has been set up, but before the function dispatch loop starts.
This permits supplying a custom child main function that inherits
rich data structures that cannot normally be passed via a
serialization.
:param Context via:
Same as the `via` parameter for :py:meth:`local`.
:param bool debug:
Same as the `debug` parameter for :py:meth:`local`.
:param bool profiling:
Same as the `profiling` parameter for :py:meth:`local`.
.. method:: local (remote_name=None, python_path=None, debug=False, connect_timeout=None, profiling=False, via=None)
Construct a context on the local machine as a subprocess of the current
process. The associated stream implementation is
:py:class:`mitogen.master.Stream`.
:param str remote_name:
The ``argv[0]`` suffix for the new process. If `remote_name` is
``test``, the new process ``argv[0]`` will be ``mitogen:test``.
If unspecified, defaults to ``<username>@<hostname>:<pid>``.
This variable cannot contain slash characters, as the resulting
``argv[0]`` must be presented in such a way as to allow Python to
determine its installation prefix. This is required to support
virtualenv.
:param str python_path:
Path to the Python interpreter to use for bootstrap. Defaults to
``python2.7``. In future this may default to ``sys.executable``.
:param bool debug:
If :data:`True`, arrange for debug logging (:py:meth:`enable_debug`) to
be enabled in the new context. Automatically :data:`True` when
:py:meth:`enable_debug` has been called, but may be used
selectively otherwise.
:param bool unidirectional:
If :data:`True`, arrange for the child's router to be constructed
with :attr:`unidirectional routing
<mitogen.core.Router.unidirectional>` enabled. Automatically
:data:`True` when it was enabled for this router, but may still be
explicitly set to :data:`False`.
:param float connect_timeout:
Fractional seconds to wait for the subprocess to indicate it is
healthy. Defaults to 30 seconds.
:param bool profiling:
If :data:`True`, arrange for profiling (:py:data:`profiling`) to be
enabled in the new context. Automatically :data:`True` when
:py:data:`profiling` is :data:`True`, but may be used selectively
otherwise.
:param mitogen.core.Context via:
If not ``None``, arrange for construction to occur via RPCs made to
the context `via`, and for :py:data:`ADD_ROUTE
<mitogen.core.ADD_ROUTE>` messages to be generated as appropriate.
.. code-block:: python
# SSH to the remote machine.
remote_machine = router.ssh(hostname='mybox.com')
# Use the SSH connection to create a sudo connection.
remote_root = router.sudo(username='root', via=remote_machine)
.. method:: docker (container=None, image=None, docker_path=None, \**kwargs)
Construct a context on the local machine within an existing or
temporary new Docker container using the ``docker`` program. One of
`container` or `image` must be specified.
Accepts all parameters accepted by :py:meth:`local`, in addition to:
:param str container:
Existing container to connect to. Defaults to :data:`None`.
:param str username:
Username within the container to :func:`setuid` to. Defaults to
:data:`None`, which Docker interprets as ``root``.
:param str image:
Image tag to use to construct a temporary container. Defaults to
``None``.
:param str docker_path:
Filename or complete path to the Docker binary. ``PATH`` will be
searched if given as a filename. Defaults to ``docker``.
.. method:: jail (container, jexec_path=None, \**kwargs)
Construct a context on the local machine within a FreeBSD jail using
the ``jexec`` program.
Accepts all parameters accepted by :py:meth:`local`, in addition to:
:param str container:
Existing container to connect to. Defaults to :data:`None`.
:param str username:
Username within the container to :func:`setuid` to. Defaults to
:data:`None`, which ``jexec`` interprets as ``root``.
:param str jexec_path:
Filename or complete path to the ``jexec`` binary. ``PATH`` will be
searched if given as a filename. Defaults to ``/usr/sbin/jexec``.
.. method:: lxc (container, lxc_attach_path=None, \**kwargs)
Construct a context on the local machine within an LXC container using
the ``lxc-attach`` program.
Accepts all parameters accepted by :py:meth:`local`, in addition to:
:param str container:
Existing container to connect to. Defaults to ``None``.
:param str lxc_attach_path:
Filename or complete path to the ``lxc-attach`` binary. ``PATH``
will be searched if given as a filename. Defaults to
``lxc-attach``.
.. method:: setns (container, kind, docker_path=None, lxc_info_path=None, machinectl_path=None, \**kwargs)
Construct a context in the style of :meth:`local`, but change the
active Linux process namespaces via calls to `setns(1)` before
executing Python.
The namespaces to use, and the active root file system are taken from
the root PID of a running Docker, LXC, or systemd-nspawn container.
A program is required only to find the root PID, after which management
of the child Python interpreter is handled directly.
:param str container:
Container to connect to.
:param str kind:
One of ``docker``, ``lxc`` or ``machinectl``.
:param str docker_path:
Filename or complete path to the Docker binary. ``PATH`` will be
searched if given as a filename. Defaults to ``docker``.
:param str lxc_info_path:
Filename or complete path to the ``lxc-info`` binary. ``PATH``
will be searched if given as a filename. Defaults to
``lxc-info``.
:param str machinectl_path:
Filename or complete path to the ``machinectl`` binary. ``PATH``
will be searched if given as a filename. Defaults to
``machinectl``.
.. method:: su (username=None, password=None, su_path=None, password_prompt=None, incorrect_prompts=None, \**kwargs)
Construct a context on the local machine over a ``su`` invocation. The
``su`` process is started in a newly allocated pseudo-terminal, and
supports typing interactive passwords.
Accepts all parameters accepted by :py:meth:`local`, in addition to:
:param str username:
Username to pass to ``su``, defaults to ``root``.
:param str password:
The account password to use if requested.
:param str su_path:
Filename or complete path to the ``su`` binary. ``PATH`` will be
searched if given as a filename. Defaults to ``su``.
:param str password_prompt:
The string to wait to that signals ``su`` is requesting a password.
Defaults to ``Password:``.
:param str password_prompt:
The string that signal a request for the password. Defaults to
``Password:``.
:param str incorrect_prompts:
Strings that signal the password is incorrect. Defaults to `("su:
sorry", "su: authentication failure")`.
:raises mitogen.su.PasswordError:
A password was requested but none was provided, the supplied
password was incorrect, or (on BSD) the target account did not
exist.
.. method:: sudo (username=None, sudo_path=None, password=None, \**kwargs)
Construct a context on the local machine over a ``sudo`` invocation.
The ``sudo`` process is started in a newly allocated pseudo-terminal,
and supports typing interactive passwords.
Accepts all parameters accepted by :py:meth:`local`, in addition to:
:param str username:
Username to pass to sudo as the ``-u`` parameter, defaults to
``root``.
:param str sudo_path:
Filename or complete path to the sudo binary. ``PATH`` will be
searched if given as a filename. Defaults to ``sudo``.
:param str password:
The password to use if/when sudo requests it. Depending on the sudo
configuration, this is either the current account password or the
target account password. :py:class:`mitogen.sudo.PasswordError`
will be raised if sudo requests a password but none is provided.
:param bool set_home:
If :py:data:`True`, request ``sudo`` set the ``HOME`` environment
variable to match the target UNIX account.
:param bool preserve_env:
If :py:data:`True`, request ``sudo`` to preserve the environment of
the parent process.
:param list sudo_args:
Arguments in the style of :py:data:`sys.argv` that would normally
be passed to ``sudo``. The arguments are parsed in-process to set
equivalent parameters. Re-parsing ensures unsupported options cause
:py:class:`mitogen.core.StreamError` to be raised, and that
attributes of the stream match the actual behaviour of ``sudo``.
.. method:: ssh (hostname, username=None, ssh_path=None, port=None, check_host_keys='enforce', password=None, identity_file=None, compression=True, \**kwargs)
Construct a remote context over a ``ssh`` invocation. The ``ssh``
process is started in a newly allocated pseudo-terminal, and supports
typing interactive passwords.
Accepts all parameters accepted by :py:meth:`local`, in addition to:
:param str username:
The SSH username; default is unspecified, which causes SSH to pick
the username to use.
:param str ssh_path:
Absolute or relative path to ``ssh``. Defaults to ``ssh``.
:param int port:
Port number to connect to; default is unspecified, which causes SSH
to pick the port number.
:param str check_host_keys:
Specifies the SSH host key checking mode. Defaults to ``enforce``.
* ``ignore``: no host key checking is performed. Connections never
fail due to an unknown or changed host key.
* ``accept``: known hosts keys are checked to ensure they match,
new host keys are automatically accepted and verified in future
connections.
* ``enforce``: known host keys are checked to ensure they match,
unknown hosts cause a connection failure.
:param str password:
Password to type if/when ``ssh`` requests it. If not specified and
a password is requested, :py:class:`mitogen.ssh.PasswordError` is
raised.
:param str identity_file:
Path to an SSH private key file to use for authentication. Default
is unspecified, which causes SSH to pick the identity file.
When this option is specified, only `identity_file` will be used by
the SSH client to perform authenticaion; agent authentication is
automatically disabled, as is reading the default private key from
``~/.ssh/id_rsa``, or ``~/.ssh/id_dsa``.
:param bool compression:
If :py:data:`True`, enable ``ssh`` compression support. Compression
has a minimal effect on the size of modules transmitted, as they
are already compressed, however it has a large effect on every
remaining message in the otherwise uncompressed stream protocol,
such as function call arguments and return values.
:raises mitogen.ssh.PasswordError:
A password was requested but none was specified, or the specified
password was incorrect.
:raises mitogen.ssh.HostKeyError:
When `check_host_keys` is set to either ``accept``, indicates a
previously recorded key no longer matches the remote machine. When
set to ``enforce``, as above, but additionally indicates no
previously recorded key exists for the remote machine.
Context Class
=============
.. currentmodule:: mitogen.core
.. class:: Context
Represent a remote context regardless of connection method.
**Note:** This is the somewhat limited core version of the Context class
used by child contexts. The master subclass is documented below this one.
.. method:: send (msg)
Arrange for `msg` to be delivered to this context. Updates the
message's `dst_id` prior to routing it via the associated router.
:param mitogen.core.Message msg:
The message.
.. method:: send_async (msg, persist=False)
Arrange for `msg` to be delivered to this context, with replies
delivered to a newly constructed Receiver. Updates the message's
`dst_id` prior to routing it via the associated router and registers a
handle which is placed in the message's `reply_to`.
:param bool persist:
If ``False``, the handler will be unregistered after a single
message has been received.
:param mitogen.core.Message msg:
The message.
:returns:
:py:class:`mitogen.core.Receiver` configured to receive any replies
sent to the message's `reply_to` handle.
.. method:: send_await (msg, deadline=None)
As with :py:meth:`send_async`, but expect a single reply
(`persist=False`) delivered within `deadline` seconds.
:param mitogen.core.Message msg:
The message.
:param float deadline:
If not ``None``, seconds before timing out waiting for a reply.
:raises mitogen.core.TimeoutError:
No message was received and `deadline` passed.
.. currentmodule:: mitogen.parent
.. class:: Context
Extend :py:class:`mitogen.core.Router` with functionality useful to
masters, and child contexts who later become parents. Currently when this
class is required, the target context's router is upgraded at runtime.
.. method:: shutdown (wait=False)
Arrange for the context to receive a ``SHUTDOWN`` message, triggering
graceful shutdown.
Due to a lack of support for timers, no attempt is made yet to force
terminate a hung context using this method. This will be fixed shortly.
:param bool wait:
If :py:data:`True`, block the calling thread until the context has
completely terminated.
:returns:
If `wait` is :data:`False`, returns a :class:`mitogen.core.Latch`
whose :meth:`get() <mitogen.core.Latch.get>` method returns
:data:`None` when shutdown completes. The `timeout` parameter may
be used to implement graceful timeouts.
.. method:: call_async (fn, \*args, \*\*kwargs)
Arrange for the context's ``CALL_FUNCTION`` handle to receive a
message that causes `fn(\*args, \**kwargs)` to be invoked on the
context's main thread.
:param fn:
A free function in module scope, or a classmethod or staticmethod
of a class directly reachable from module scope:
.. code-block:: python
# mymodule.py
def my_func():
"""A free function reachable as mymodule.my_func"""
class MyClass:
@staticmethod
def my_staticmethod():
"""Reachable as mymodule.MyClass.my_staticmethod"""
@classmethod
def my_classmethod(cls):
"""Reachable as mymodule.MyClass.my_classmethod"""
def my_instancemethod(self):
"""Unreachable: requires a class instance!"""
class MyEmbeddedClass:
@classmethod
def my_classmethod(cls):
"""Not directly reachable from module scope!"""
:param tuple args:
Function arguments, if any. See :ref:`serialization-rules` for
permitted types.
:param dict kwargs:
Function keyword arguments, if any. See :ref:`serialization-rules`
for permitted types.
:returns:
:py:class:`mitogen.core.Receiver` configured to receive the result
of the invocation:
.. code-block:: python
recv = context.call_async(os.check_output, 'ls /tmp/')
try:
# Prints output once it is received.
msg = recv.get()
print msg.unpickle()
except mitogen.core.CallError, e:
print 'Call failed:', str(e)
Asynchronous calls may be dispatched in parallel to multiple
contexts and consumed as they complete using
:py:class:`mitogen.select.Select`.
.. method:: call (fn, \*args, \*\*kwargs)
Equivalent to :py:meth:`call_async(fn, \*args, \**kwargs).get_data()
<call_async>`.
:returns:
The function's return value.
:raises mitogen.core.CallError:
An exception was raised in the remote context during execution.
Receiver Class
==============
.. currentmodule:: mitogen.core
.. class:: Receiver (router, handle=None, persist=True, respondent=None)
Receivers are used to wait for pickled responses from another context to be
sent to a handle registered in this context. A receiver may be single-use
(as in the case of :py:meth:`mitogen.parent.Context.call_async`) or
multiple use.
:param mitogen.core.Router router:
Router to register the handler on.
:param int handle:
If not ``None``, an explicit handle to register, otherwise an unused
handle is chosen.
:param bool persist:
If :data:`True`, do not unregister the receiver's handler after the
first message.
:param mitogen.core.Context respondent:
Reference to the context this receiver is receiving from. If not
``None``, arranges for the receiver to receive a dead message if
messages can no longer be routed to the context, due to disconnection
or exit.
.. attribute:: notify = None
If not ``None``, a reference to a function invoked as
`notify(receiver)` when a new message is delivered to this receiver.
Used by :py:class:`mitogen.select.Select` to implement waiting on
multiple receivers.
.. py:method:: to_sender ()
Return a :py:class:`mitogen.core.Sender` configured to deliver messages
to this receiver. Since a Sender can be serialized, this makes it
convenient to pass `(context_id, handle)` pairs around::
def deliver_monthly_report(sender):
for line in open('monthly_report.txt'):
sender.send(line)
sender.close()
remote = router.ssh(hostname='mainframe')
recv = mitogen.core.Receiver(router)
remote.call(deliver_monthly_report, recv.to_sender())
for msg in recv:
print(msg)
.. py:method:: empty ()
Return :data:`True` if calling :py:meth:`get` would block.
As with :py:class:`Queue.Queue`, :data:`True` may be returned even
though a subsequent call to :py:meth:`get` will succeed, since a
message may be posted at any moment between :py:meth:`empty` and
:py:meth:`get`.
:py:meth:`empty` is only useful to avoid a race while installing
:py:attr:`notify`:
.. code-block:: python
recv.notify = _my_notify_function
if not recv.empty():
_my_notify_function(recv)
# It is guaranteed the receiver was empty after the notification
# function was installed, or that it was non-empty and the
# notification function was invoked at least once.
.. py:method:: close ()
Cause :py:class:`mitogen.core.ChannelError` to be raised in any thread
waiting in :py:meth:`get` on this receiver.
.. py:method:: get (timeout=None)
Sleep waiting for a message to arrive on this receiver.
:param float timeout:
If not ``None``, specifies a timeout in seconds.
:raises mitogen.core.ChannelError:
The remote end indicated the channel should be closed, or
communication with its parent context was lost.
:raises mitogen.core.TimeoutError:
Timeout was reached.
:returns:
`(msg, data)` tuple, where `msg` is the
:py:class:`mitogen.core.Message` that was received, and `data` is
its unpickled data part.
.. py:method:: get_data (timeout=None)
Like :py:meth:`get`, except only return the data part.
.. py:method:: __iter__ ()
Block and yield `(msg, data)` pairs delivered to this receiver until
:py:class:`mitogen.core.ChannelError` is raised.
Sender Class
============
.. currentmodule:: mitogen.core
.. class:: Sender (context, dst_handle)
Senders are used to send pickled messages to a handle in another context,
it is the inverse of :py:class:`mitogen.core.Sender`.
Senders may be serialized, making them convenient to wire up data flows.
See :py:meth:`mitogen.core.Receiver.to_sender` for more information.
:param mitogen.core.Context context:
Context to send messages to.
:param int dst_handle:
Destination handle to send messages to.
.. py:method:: close ()
Send a dead message to the remote end, causing :py:meth:`ChannelError`
to be raised in any waiting thread.
.. py:method:: send (data)
Send `data` to the remote end.
Select Class
============
.. module:: mitogen.select
.. currentmodule:: mitogen.select
.. class:: Select (receivers=(), oneshot=True)
Support scatter/gather asynchronous calls and waiting on multiple
receivers, channels, and sub-Selects. Accepts a sequence of
:py:class:`mitogen.core.Receiver` or :py:class:`mitogen.select.Select`
instances and returns the first value posted to any receiver or select.
If `oneshot` is :data:`True`, then remove each receiver as it yields a
result; since :py:meth:`__iter__` terminates once the final receiver is
removed, this makes it convenient to respond to calls made in parallel:
.. code-block:: python
total = 0
recvs = [c.call_async(long_running_operation) for c in contexts]
for msg in mitogen.select.Select(recvs):
print 'Got %s from %s' % (msg, msg.receiver)
total += msg.unpickle()
# Iteration ends when last Receiver yields a result.
print 'Received total %s from %s receivers' % (total, len(recvs))
:py:class:`Select` may drive a long-running scheduler:
.. code-block:: python
with mitogen.select.Select(oneshot=False) as select:
while running():
for msg in select:
process_result(msg.receiver.context, msg.unpickle())
for context, workfunc in get_new_work():
select.add(context.call_async(workfunc))
:py:class:`Select` may be nested:
.. code-block:: python
subselects = [
mitogen.select.Select(get_some_work()),
mitogen.select.Select(get_some_work()),
mitogen.select.Select([
mitogen.select.Select(get_some_work()),
mitogen.select.Select(get_some_work())
])
]
for msg in mitogen.select.Select(selects):
print msg.unpickle()
.. py:classmethod:: all (it)
Take an iterable of receivers and retrieve a :py:class:`Message` from
each, returning the result of calling `msg.unpickle()` on each in turn.
Results are returned in the order they arrived.
This is sugar for handling batch :py:class:`Context.call_async`
invocations:
.. code-block:: python
print('Total disk usage: %.02fMiB' % (sum(
mitogen.select.Select.all(
context.call_async(get_disk_usage)
for context in contexts
) / 1048576.0
),))
However, unlike in a naive comprehension such as:
.. code-block:: python
sum(context.call_async(get_disk_usage).get().unpickle()
for context in contexts)
Result processing happens concurrently to new results arriving, so
:py:meth:`all` should always be faster.
.. py:method:: get (timeout=None, block=True)
Fetch the next available value from any receiver, or raise
:py:class:`mitogen.core.TimeoutError` if no value is available within
`timeout` seconds.
On success, the message's :py:attr:`receiver
<mitogen.core.Message.receiver>` attribute is set to the receiver.
:param float timeout:
Timeout in seconds.
:param bool block:
If :py:data:`False`, immediately raise
:py:class:`mitogen.core.TimeoutError` if the select is empty.
:return:
:py:class:`mitogen.core.Message`
:raises mitogen.core.TimeoutError:
Timeout was reached.
:raises mitogen.core.LatchError:
:py:meth:`close` has been called, and the underlying latch is no
longer valid.
.. py:method:: __bool__ ()
Return :data:`True` if any receivers are registered with this select.
.. py:method:: close ()
Remove the select's notifier function from each registered receiver,
mark the associated latch as closed, and cause any thread currently
sleeping in :py:meth:`get` to be woken with
:py:class:`mitogen.core.LatchError`.
This is necessary to prevent memory leaks in long-running receivers. It
is called automatically when the Python :keyword:`with` statement is
used.
.. py:method:: empty ()
Return :data:`True` if calling :py:meth:`get` would block.
As with :py:class:`Queue.Queue`, :data:`True` may be returned even
though a subsequent call to :py:meth:`get` will succeed, since a
message may be posted at any moment between :py:meth:`empty` and
:py:meth:`get`.
:py:meth:`empty` may return ``False`` even when :py:meth:`get` would
block if another thread has drained a receiver added to this select.
This can be avoided by only consuming each receiver from a single
thread.
.. py:method:: __iter__ (self)
Yield the result of :py:meth:`get` until no receivers remain in the
select, either because `oneshot` is :data:`True`, or each receiver was
explicitly removed via :py:meth:`remove`.
.. py:method:: add (recv)
Add the :py:class:`mitogen.core.Receiver` or
:py:class:`mitogen.core.Channel` `recv` to the select.
.. py:method:: remove (recv)
Remove the :py:class:`mitogen.core.Receiver` or
:py:class:`mitogen.core.Channel` `recv` from the select. Note that if
the receiver has notified prior to :py:meth:`remove`, then it will
still be returned by a subsequent :py:meth:`get`. This may change in a
future version.
Channel Class
=============
.. currentmodule:: mitogen.core
.. class:: Channel (router, context, dst_handle, handle=None)
A channel inherits from :py:class:`mitogen.core.Sender` and
`mitogen.core.Receiver` to provide bidirectional functionality.
Since all handles aren't known until after both ends are constructed, for
both ends to communicate through a channel, it is necessary for one end to
retrieve the handle allocated to the other and reconfigure its own channel
to match. Currently this is a manual task.
Broker Class
============
.. currentmodule:: mitogen.core
.. class:: Broker
Responsible for handling I/O multiplexing in a private thread.
**Note:** This is the somewhat limited core version of the Broker class
used by child contexts. The master subclass is documented below this one.
.. attribute:: shutdown_timeout = 3.0
Seconds grace to allow :py:class:`streams <Stream>` to shutdown
gracefully before force-disconnecting them during :py:meth:`shutdown`.
.. method:: defer (func, \*args, \*kwargs)
Arrange for `func(\*args, \**kwargs)` to be executed on the broker
thread, or immediately if the current thread is the broker thread. Safe
to call from any thread.
.. method:: start_receive (stream)
Mark the :py:attr:`receive_side <Stream.receive_side>` on `stream` as
ready for reading. Safe to call from any thread. When the associated
file descriptor becomes ready for reading,
:py:meth:`BasicStream.on_receive` will be called.
.. method:: stop_receive (stream)
Mark the :py:attr:`receive_side <Stream.receive_side>` on `stream` as
not ready for reading. Safe to call from any thread.
.. method:: _start_transmit (stream)
Mark the :py:attr:`transmit_side <Stream.transmit_side>` on `stream` as
ready for writing. Must only be called from the Broker thread. When the
associated file descriptor becomes ready for writing,
:py:meth:`BasicStream.on_transmit` will be called.
.. method:: stop_receive (stream)
Mark the :py:attr:`transmit_side <Stream.receive_side>` on `stream` as
not ready for writing. Safe to call from any thread.
.. method:: shutdown
Request broker gracefully disconnect streams and stop.
.. method:: join
Wait for the broker to stop, expected to be called after
:py:meth:`shutdown`.
.. method:: keep_alive
Return :data:`True` if any reader's :py:attr:`Side.keep_alive`
attribute is :data:`True`, or any :py:class:`Context` is still
registered that is not the master. Used to delay shutdown while some
important work is in progress (e.g. log draining).
**Internal Methods**
.. method:: _broker_main
Handle events until :py:meth:`shutdown`. On shutdown, invoke
:py:meth:`Stream.on_shutdown` for every active stream, then allow up to
:py:attr:`shutdown_timeout` seconds for the streams to unregister
themselves before forcefully calling
:py:meth:`Stream.on_disconnect`.
.. currentmodule:: mitogen.master
.. class:: Broker (install_watcher=True)
.. note::
You may construct as many brokers as desired, and use the same broker
for multiple routers, however usually only one broker need exist.
Multiple brokers may be useful when dealing with sets of children with
differing lifetimes. For example, a subscription service where
non-payment results in termination for one customer.
:param bool install_watcher:
If :data:`True`, an additional thread is started to monitor the
lifetime of the main thread, triggering :py:meth:`shutdown`
automatically in case the user forgets to call it, or their code
crashed.
You should not rely on this functionality in your program, it is only
intended as a fail-safe and to simplify the API for new users. In
particular, alternative Python implementations may not be able to
support watching the main thread.
.. attribute:: shutdown_timeout = 5.0
Seconds grace to allow :py:class:`streams <Stream>` to shutdown
gracefully before force-disconnecting them during :py:meth:`shutdown`.
Utility Functions
=================
.. module:: mitogen.utils
A random assortment of utility functions useful on masters and children.
.. currentmodule:: mitogen.utils
.. function:: cast (obj)
Many tools love to subclass built-in types in order to implement useful
functionality, such as annotating the safety of a Unicode string, or adding
additional methods to a dict. However, cPickle loves to preserve those
subtypes during serialization, resulting in CallError during :py:meth:`call
<mitogen.parent.Context.call>` in the target when it tries to deserialize
the data.
This function walks the object graph `obj`, producing a copy with any
custom sub-types removed. The functionality is not default since the
resulting walk may be computationally expensive given a large enough graph.
See :ref:`serialization-rules` for a list of supported types.
:param obj:
Object to undecorate.
:returns:
Undecorated object.
.. currentmodule:: mitogen.utils
.. function:: disable_site_packages
Remove all entries mentioning ``site-packages`` or ``Extras`` from the
system path. Used primarily for testing on OS X within a virtualenv, where
OS X bundles some ancient version of the :py:mod:`six` module.
.. currentmodule:: mitogen.utils
.. function:: log_to_file (path=None, io=False, usec=False, level='INFO')
Install a new :py:class:`logging.Handler` writing applications logs to the
filesystem. Useful when debugging slave IO problems.
Parameters to this function may be overridden at runtime using environment
variables. See :ref:`logging-env-vars`.
:param str path:
If not ``None``, a filesystem path to write logs to. Otherwise, logs
are written to :py:data:`sys.stderr`.
:param bool io:
If :data:`True`, include extremely verbose IO logs in the output.
Useful for debugging hangs, less useful for debugging application code.
:parm bool usec:
If :data:`True`, include microsecond timestamps. This greatly helps
when debugging races and similar determinism issues.
:param str level:
Name of the :py:mod:`logging` package constant that is the minimum
level to log at. Useful levels are ``DEBUG``, ``INFO``, ``WARNING``,
and ``ERROR``.
.. currentmodule:: mitogen.utils
.. function:: run_with_router(func, \*args, \**kwargs)
Arrange for `func(router, \*args, \**kwargs)` to run with a temporary
:py:class:`mitogen.master.Router`, ensuring the Router and Broker are
correctly shut down during normal or exceptional return.
:returns:
`func`'s return value.
.. currentmodule:: mitogen.utils
.. decorator:: with_router
Decorator version of :py:func:`run_with_router`. Example:
.. code-block:: python
@with_router
def do_stuff(router, arg):
pass
do_stuff(blah, 123)
Exceptions
==========
.. currentmodule:: mitogen.core
.. class:: Error (fmt, \*args)
Base for all exceptions raised by Mitogen.
.. class:: CallError (e)
Raised when :py:meth:`Context.call() <mitogen.parent.Context.call>` fails.
A copy of the traceback from the external context is appended to the
exception message.
.. class:: ChannelError (fmt, \*args)
Raised when a channel dies or has been closed.
.. class:: LatchError (fmt, \*args)
Raised when an attempt is made to use a :py:class:`mitogen.core.Latch` that
has been marked closed.
.. class:: StreamError (fmt, \*args)
Raised when a stream cannot be established.
.. class:: TimeoutError (fmt, \*args)
Raised when a timeout occurs on a stream.
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