Initial intro doc.

8 years ago · ce27058bdf
parent d457c20d87
commit ce27058bdf
7 changed files with 254 additions and 292 deletions
--- a/docs/api.rst
+++ b/docs/api.rst
@ -0,0 +1,19 @@
 API Reference
 =============
 econtext.core
 #############
 .. automodule:: econtext.core
   :members:
   :undoc-members:
 econtext.master
 ###############
 .. automodule:: econtext.master
   :members:
   :undoc-members:
--- a/docs/conf.py
+++ b/docs/conf.py
@ -1,285 +1,22 @@
 # -*- coding: utf-8 -*-
 #
 # econtext documentation build configuration file, created by
 # sphinx-quickstart on Thu Aug 11 18:16:36 2016.
 #
 # This file is execfile()d with the current directory set to its
 # containing dir.
 #
 # Note that not all possible configuration values are present in this
 # autogenerated file.
 #
 # All configuration values have a default; values that are commented out
 # serve to show the default.
 import sys
 import os
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 #sys.path.insert(0, os.path.abspath('.'))
 # -- General configuration ------------------------------------------------
 # If your documentation needs a minimal Sphinx version, state it here.
 #needs_sphinx = '1.0'
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
 extensions = [
    'sphinx.ext.autodoc',
 ]
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
 # The suffix(es) of source filenames.
 # You can specify multiple suffix as a list of string:
 # source_suffix = ['.rst', '.md']
 source_suffix = '.rst'
 # The encoding of source files.
 #source_encoding = 'utf-8-sig'
 # The master toctree document.
 master_doc = 'index'
 # General information about the project.
 project = u'econtext'
 copyright = u'2016, David Wilson'
 author = u'David Wilson'
-
+copyright = u'2016, David Wilson'
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the
 # built documents.
 #
 # The short X.Y version.
 version = u'master'
 # The full version, including alpha/beta/rc tags.
 release = u'master'
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
 #
 # This is also used if you do content translation via gettext catalogs.
 # Usually you set "language" from the command line for these cases.
 language = None
 # There are two options for replacing |today|: either, you set today to some
 # non-false value, then it is used:
 #today = ''
 # Else, today_fmt is used as the format for a strftime call.
 #today_fmt = '%B %d, %Y'
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.
 exclude_patterns = ['_build']
-
+extensions = ['sphinx.ext.autodoc']
-# The reST default role (used for this markup: `text`) to use for all
+html_show_sourcelink = False
-# documents.
+html_show_sphinx = False
-#default_role = None
+html_sidebars = {'**': ['globaltoc.html']}
 # If true, '()' will be appended to :func: etc. cross-reference text.
 #add_function_parentheses = True
 # If true, the current module name will be prepended to all description
 # unit titles (such as .. function::).
 #add_module_names = True
 # If true, sectionauthor and moduleauthor directives will be shown in the
 # output. They are ignored by default.
 #show_authors = False
 # The name of the Pygments (syntax highlighting) style to use.
 pygments_style = 'sphinx'
 # A list of ignored prefixes for module index sorting.
 #modindex_common_prefix = []
 # If true, keep warnings as "system message" paragraphs in the built documents.
 #keep_warnings = False
 # If true, `todo` and `todoList` produce output, else they produce nothing.
 todo_include_todos = False
 # -- Options for HTML output ----------------------------------------------
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
 html_theme = 'alabaster'
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the
 # documentation.
 #html_theme_options = {}
 # Add any paths that contain custom themes here, relative to this directory.
 #html_theme_path = []
 # The name for this set of Sphinx documents.  If None, it defaults to
 # "<project> v<release> documentation".
 #html_title = None
 # A shorter title for the navigation bar.  Default is the same as html_title.
 #html_short_title = None
 # The name of an image file (relative to this directory) to place at the top
 # of the sidebar.
 #html_logo = None
 # The name of an image file (within the static path) to use as favicon of the
 # docs.  This file should be a Windows icon file (.ico) being 16x16 or 32x32
 # pixels large.
 #html_favicon = None
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".
 html_static_path = ['_static']
-
+html_theme = 'alabaster'
 # Add any extra paths that contain custom files (such as robots.txt or
 # .htaccess) here, relative to this directory. These files are copied
 # directly to the root of the documentation.
 #html_extra_path = []
 # If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
 # using the given strftime format.
 #html_last_updated_fmt = '%b %d, %Y'
 # If true, SmartyPants will be used to convert quotes and dashes to
 # typographically correct entities.
 #html_use_smartypants = True
 # Custom sidebar templates, maps document names to template names.
 #html_sidebars = {}
 # Additional templates that should be rendered to pages, maps page names to
 # template names.
 #html_additional_pages = {}
 # If false, no module index is generated.
 #html_domain_indices = True
 # If false, no index is generated.
 #html_use_index = True
 # If true, the index is split into individual pages for each letter.
 #html_split_index = False
 # If true, links to the reST sources are added to the pages.
 #html_show_sourcelink = True
 # If true, "Created using Sphinx" is shown in the HTML footer. Default is True.
 #html_show_sphinx = True
 # If true, "(C) Copyright ..." is shown in the HTML footer. Default is True.
 #html_show_copyright = True
 # If true, an OpenSearch description file will be output, and all pages will
 # contain a <link> tag referring to it.  The value of this option must be the
 # base URL from which the finished HTML is served.
 #html_use_opensearch = ''
 # This is the file name suffix for HTML files (e.g. ".xhtml").
 #html_file_suffix = None
 # Language to be used for generating the HTML full-text search index.
 # Sphinx supports the following languages:
 #   'da', 'de', 'en', 'es', 'fi', 'fr', 'hu', 'it', 'ja'
 #   'nl', 'no', 'pt', 'ro', 'ru', 'sv', 'tr'
 #html_search_language = 'en'
 # A dictionary with options for the search language support, empty by default.
 # Now only 'ja' uses this config value
 #html_search_options = {'type': 'default'}
 # The name of a javascript file (relative to the configuration directory) that
 # implements a search results scorer. If empty, the default will be used.
 #html_search_scorer = 'scorer.js'
 # Output file base name for HTML help builder.
 htmlhelp_basename = 'econtextdoc'
-
+language = None
-# -- Options for LaTeX output ---------------------------------------------
+master_doc = 'index'
-
+project = u'econtext'
-latex_elements = {
+pygments_style = 'sphinx'
-# The paper size ('letterpaper' or 'a4paper').
+release = u'master'
-#'papersize': 'letterpaper',
+source_suffix = '.rst'
-
+templates_path = ['_templates']
-# The font size ('10pt', '11pt' or '12pt').
+todo_include_todos = False
-#'pointsize': '10pt',
+version = u'master'
 # Additional stuff for the LaTeX preamble.
 #'preamble': '',
 # Latex figure (float) alignment
 #'figure_align': 'htbp',
 }
 # Grouping the document tree into LaTeX files. List of tuples
 # (source start file, target name, title,
 #  author, documentclass [howto, manual, or own class]).
 latex_documents = [
    (master_doc, 'econtext.tex', u'econtext Documentation',
     u'David Wilson', 'manual'),
 ]
 # The name of an image file (relative to this directory) to place at the top of
 # the title page.
 #latex_logo = None
 # For "manual" documents, if this is true, then toplevel headings are parts,
 # not chapters.
 #latex_use_parts = False
 # If true, show page references after internal links.
 #latex_show_pagerefs = False
 # If true, show URL addresses after external links.
 #latex_show_urls = False
 # Documents to append as an appendix to all manuals.
 #latex_appendices = []
 # If false, no module index is generated.
 #latex_domain_indices = True
 # -- Options for manual page output ---------------------------------------
 # One entry per manual page. List of tuples
 # (source start file, name, description, authors, manual section).
 man_pages = [
    (master_doc, 'econtext', u'econtext Documentation',
     [author], 1)
 ]
 # If true, show URL addresses after external links.
 #man_show_urls = False
 # -- Options for Texinfo output -------------------------------------------
 # Grouping the document tree into Texinfo files. List of tuples
 # (source start file, target name, title, author,
 #  dir menu entry, description, category)
 texinfo_documents = [
    (master_doc, 'econtext', u'econtext Documentation',
     author, 'econtext', 'One line description of project.',
     'Miscellaneous'),
 ]
 # Documents to append as an appendix to all manuals.
 #texinfo_appendices = []
 # If false, no module index is generated.
 #texinfo_domain_indices = True
 # How to display URL addresses: 'footnote', 'no', or 'inline'.
 #texinfo_show_urls = 'footnote'
 # If true, do not generate a @detailmenu in the "Top" node's menu.
 #texinfo_no_detailmenu = False
--- a/docs/getting_started.rst
+++ b/docs/getting_started.rst
@ -0,0 +1,5 @@
 Getting Started
 ===============
 xxx
--- a/docs/howitworks.rst
+++ b/docs/howitworks.rst
@ -0,0 +1,7 @@
 How econtext Works
 ------------------
 blah blah
--- a/docs/index.rst
+++ b/docs/index.rst
@ -1,22 +1,209 @@
 .. econtext documentation master file, created by
   sphinx-quickstart on Thu Aug 11 18:16:36 2016.
   You can adapt this file completely to your liking, but it should at least
   contain the root `toctree` directive.
-Welcome to econtext's documentation!
+Python Execution Contexts
-====================================
+=========================
-Contents:
+**4.98KiB of sugar and no fat!**
 .. toctree::
-   :maxdepth: 2
+   :maxdepth: 1
   self
   howitworks
   getting_started
   api
-Indices and tables
+Introduction
-==================
+------------
-* :ref:`genindex`
+The Python ``econtext`` package implements external *execution contexts*: an
-* :ref:`modindex`
+execution context is somewhere you can run Python code external to your main
-* :ref:`search`
+process, even on a remote machine.
 **There is no requirement for installing packages, copying files around,
 writing shell scripts, upfront configuration, or providing any secondary link
 to the remote machine**. Due to the origins of econtext for use in managing
 potentially damaged infrastructure, the remote machine need not even have a
 writeable filesystem.
 It is not intended as a generic RPC framework, the goal is to provide a robust
 and efficient low-level API on which tools like **Salt** or **Ansible** can be
 built, and while the API is quite friendly and similar in scope to **Fabric**,
 ultimately it should not be used directly by consumer software.
 The primary focus is to centralize and perfect the intricate dance required to
 run Python code safely and efficiently on a remote machine, while avoiding
 temporary files or large chunks of error-prone shell scripts.
 Automatic Bootstrap
 ###################
 The package's main feature is enabling your Python program to bootstrap and
 communicate with new Python programs under its control running on remote
 machines, **using only an existing installed Python interpreter and SSH
 client**, something that by default can be found on almost all contemporary
 machines in the wild. To accomplish bootstrap, econtext uses a single 500 byte
 SSH command line and 5KB of data sent to stdin of the remote SSH connection.
 .. code::
    $ python preamble_size.py
    SSH command size: 411
    Preamble size: 5098 (4.98KiB)
    econtext.master size: 2403 (2.35KiB)
 Once bootstrapped, the remote process is configured with a customizable
 **argv[0]**, readily visible to system administrators of the remote machine
 using the UNIX **ps** command:
 .. code::
    20051 ?        Ss     0:00  \_ sshd: dmw [priv]
    20053 ?        S      0:00  |   \_ sshd: dmw@notty
    20054 ?        Ssl    0:00  |       \_ econtext:dmw@Eldil.home:22476
    20103 ?        S      0:00  |           \_ tar zxvf myapp.tar.gz
 The example context was started by UID ``dmw`` on host ``Eldil.home``, process
 ID ``22476``.
 IO Multiplexer
 ##############
 The bootstrap includes a compact IO multiplexer (like Twisted or asyncio) that
 allows it to perform work in the background while executing your program's
 code. For example, the remote context can be used to connect to a new user on
 the remote machine using **sudo**, or as an intermediary for extending the
 program's domain of control outward to other machines, enabling your program to
 manipulate machines behind a firewall, or to allow its data plane to match your
 network topology.
 The multiplexer also ensures the remote process is terminated if your Python
 program crashes, communication is lost, or the application code running in the
 context has hung.
 Module Forwarder
 ################
 In addition to an IO multiplexer, the external context is configured with a
 custom **PEP-302 importer** that forwards requests for unknown Python modules
 back to the host machine. When your program asks an external context to execute
 code from an unknown module, all requisite modules are transferred
 automatically and imported entirely in RAM without need for further
 configuration.
 .. code-block:: python
    import myapp.mypkg.mymodule
    # myapp/__init__.py, myapp/mypkg/__init__.py, and myapp/mypkg/mymodule.py
    # are transferred automatically.
    print context.call(myapp.mymodule.my_function)
 Logging Forwarder
 #################
 The 5KB bootstrap configures the remote process's Python logging package to
 forward all logs back to the local process, enabling management of program logs
 in one location.
 .. code::
    18:15:29 D econtext.ctx.k3: econtext: SlaveModuleImporter.find_module('econtext.zlib')
    18:15:29 D econtext.ctx.k3: econtext: _dispatch_calls((1002L, False, 'posix', None, 'system', ('ls -l /proc/self/fd',), {}))
 Stdio Forwarder
 ###############
 To ease porting of crusty old infrastructure code to pure Python, the bootstrap
 redirects stdio for itself and any child processes back into the logging
 framework. This allows use of functions as basic as **os.system('hostname;
 uptime')** without further need to capture or manage output.
 .. code::
   18:17:28 D econtext.ctx.k3: econtext: _dispatch_calls((1002L, False, 'posix', None, 'system', ('hostname; uptime',), {}))
   18:17:56 I econtext.ctx.k3: stdout: k3
   18:17:56 I econtext.ctx.k3: stdout: 17:37:10 up 562 days,  2:25,  5 users,  load average: 1.24, 1.13, 1.14
 Blocking Code Friendly
 ######################
 Within each process, a private thread runs the I/O multiplexer, leaving the
 main thread and any additional application threads free to perform useful work.
 While econtext is internally asynchronous, it hides this asynchrony from
 consumer code. This is since writing asynchronous code is mostly a foreign
 concept to the target application of managing infrastructure. It should be
 possible to rewrite a shell script in Python without significant restructuring,
 or mind-bending feats of comprehension to understand control flow.
 Before:
 .. code-block:: sh
    #!/bin/bash
    # Install our application.
    tar zxvf app.tar.gz
 After:
 .. code-block:: python
    def install_app():
        """
        Install our application.
        """
        os.system('tar zxvf app.tar.gz')
    context.call(install_app)
 Exceptions raised by function calls are propagated back to the parent program,
 and timeouts can be configured to ensure failed calls do not block progress of
 the parent.
 Event-driven IO
 ###############
 Code running in a remote context can be connected to a *Channel*. Channels are
 used to send data asynchronously back to the parent, without further need for
 the parent to poll for changes. This is useful for monitoring systems managing
 a large fleet of machines, or to alert the parent of unexpected state changes.
 .. code-block:: python
    def tail_log_file(channel, path='/var/log/messages'):
        """
        Forward new lines in a log file to the parent.
        """
        size = os.path.getsize(path)
        while channel.open():
            new_size = os.path.getsize(path)
            if new_size == size:
                time.sleep(1)
                continue
            elif new_size < size:
                size = 0
            fp = file(path, 'r')
            fp.seek(size)
            channel.send(fp.read(new_size - size))
            fp.close()
            size = new_size
 Compatibility
 #############
 The package is written using syntax compatible all the way back to **Python
 2.4** released November 2004, making it suitable for managing a fleet of
 potentially ancient corporate hardware. For example econtext can be used out of
 the box against Red Hat Enterprise Linux 5, which was released in 2007.
--- a/econtext/core.py
+++ b/econtext/core.py
@ -1,5 +1,7 @@
 """
-Python external execution contexts.
+This module implements most package functionality, but remains separate from
 non-essential code in order to reduce its size, as it is also implements the
 bootstrap code.
 """
 import Queue
--- a/econtext/master.py
+++ b/econtext/master.py
@ -1,3 +1,8 @@
 """
 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.
 """
 import commands
 import getpass