docs: more getting started guide

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David Wilson 7 years ago
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@ -10,12 +10,12 @@ Getting Started
Liability Waiver
----------------
.. image:: images/pandora.jpg
:align: right
Before proceeding, it is critical you understand what you're involving yourself
and possibly your team and its successors with:
.. image:: images/pandora.jpg
:align: right
* Constructing the most fundamental class, :py:class:`Broker
<mitogen.master.Broker>`, causes a new thread to be spawned, exposing a huge
class of difficult to analyse behaviours that Python software generally does
@ -26,25 +26,25 @@ and possibly your team and its successors with:
your program reached production. See :ref:`troubleshooting` for more
information.
* While high-level abstractions are provided, you must understand how Mitogen
works before depending on it. Mitogen interacts with many aspects of the
operating system, threading, SSH, sudo, sockets, TTYs, shell, Python runtime,
and timing and ordering uncertainty introduced through interaction with the
network, GIL and OS scheduling.
* While high-level abstractions are provided, they are only a convenience, you
must still understand :ref:`how Mitogen works <howitworks>` before depending
on it. Mitogen interacts with many aspects of the operating system,
threading, SSH, sudo, sockets, TTYs, shell, Python runtime, and timing and
ordering uncertainty introduced through interaction with the network, GIL and
OS scheduling.
Knowledge of this domain is typically attained through painful years of
failed attempts hacking system-level programs, and learning through continual
suffering how to debug the atrocities left behind. If you feel you lack
resources or willpower to diagnose problems independently, Mitogen is not
appropriate, prefer a higher level solution instead. Bug reports failing this
expectation risk uncharitable treatment.
appropriate, prefer a higher level solution instead.
Broker And Router
-----------------
.. image:: images/layout.png
.. currentmodule:: mitogen.master
.. currentmodule:: mitogen.core
Execution starts when your program constructs a :py:class:`Broker` and
associated :py:class:`Router`. The broker is responsible for multiplexing IO to
@ -56,9 +56,7 @@ is lost.
to a callback from the broker thread (registered by :py:meth:`add_handler()
<mitogen.core.Router.add_handler>`), or forwarding them to a :py:class:`Stream
<mitogen.core.Stream>`. See :ref:`routing` for an in-depth description.
:py:class:`Router` also doubles as the entry point to Mitogen's public API:
.. code-block:: python
:py:class:`Router` also doubles as the entry point to Mitogen's public API::
>>> import mitogen.master
@ -74,9 +72,7 @@ to a callback from the broker thread (registered by :py:meth:`add_handler()
As Python will not stop if threads still exist after the main thread exits,
:py:meth:`Broker.shutdown` must be called reliably at exit. Helpers are
provided by :py:mod:`mitogen.utils` to ensure :py:class:`Broker` is reliably
destroyed:
.. code-block:: python
destroyed::
def do_mitogen_stuff(router):
# Your code here.
@ -84,7 +80,7 @@ destroyed:
mitogen.utils.run_with_router(do_mitogen_stuff)
If your program cannot live beneath :py:func:`mitogen.utils.run_with_router` on
the stack, you must must arrange for :py:meth:`Broker.shutdown` to be called
the stack, you must arrange for :py:meth:`Broker.shutdown` to be called
anywhere the main thread may exit.
.. note::
@ -111,9 +107,7 @@ Mitogen makes heavy use of the :py:mod:`logging` package, both for child
You should always configure the :py:mod:`logging` package in any program that
integrates Mitogen. If your program does not otherwise use the
:py:mod:`logging` package, a basic configuration can be performed by calling
:py:func:`mitogen.utils.log_to_file`:
.. code-block:: python
:py:func:`mitogen.utils.log_to_file`::
>>> import mitogen.utils
@ -136,9 +130,7 @@ the local machine, in another user account via `sudo`, on a remote machine via
Now a :py:class:`Router` exists, our first :py:class:`contexts <Context>` can
be created. To demonstrate basic functionality, we will start with some
:py:meth:`local() <Router.local>` contexts created as subprocesses:
.. code-block:: python
:py:meth:`local() <Router.local>` contexts created as subprocesses::
>>> local = router.local()
>>> local_with_name = router.local(remote_name='i-have-a-name')
@ -167,8 +159,78 @@ started the context, however as shown, this can be overridden.
Calling A Function
------------------
Now that we have some contexts created, it is time to execute some code in
them.
.. currentmodule:: mitogen.master
Now that some contexts exist, it is time to execute code in them. Any regular
function, static method, or class method reachable directly from module scope
may be used, including built-in functions such as :func:`time.time`.
The :py:meth:`Context.call` method is used to execute a function and block the
caller until the return value is available or an exception is raised::
>>> import time
>>> import os
>>> # Returns the current time.
>>> print 'Time in remote context:', local.call(time.time)
>>> try:
... # Raises OSError.
... local.call(os.chdir, '/nonexistent')
... except mitogen.core.CallError, e:
... print 'Call failed:', str(e)
It is a simple wrapper around the more flexible :meth:`Context.call_async`,
which immediately returns a :class:`Receiver <mitogen.core.Receiver>` wired up
to receive the return value instead. A receiver may simply be discarded, kept
around indefinitely without ever reading its result, or used to wait on the
results from several calls. Here :meth:`get_data() <mitogen.core.Receiver.get>`
is called to block the thread until the result arrives::
>>> call = local.call_async(time.time)
>>> print call.get_data()
1507292737.75547
Running User Functions
----------------------
So far we have used the interactive interpreter to call some standard library
functions, but if since source code typed at the interpreter cannot be
recovered, Mitogen is unable to execute functions defined in this way.
We must therefore continue by writing our code as a script::
# first-script.py
import mitogen.utils
def my_first_function():
print 'Hello from remote context!'
return 123
def main(router):
local = router.local()
print local.call(my_first_function)
if __name__ == '__main__':
mitogen.utils.log_to_file(main)
mitogen.utils.run_with_router(main)
Let's try running it:
.. code-block:: bash
$ python first-script.py
19:11:32 I mitogen.ctx.local.32466: stdout: Hello from remote context!
123
Waiting On Multiple Calls
-------------------------
Recursion

@ -1,4 +1,6 @@
.. _howitworks:
How Mitogen Works
=================

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