view tests/test-minirst.py @ 26623:5a95fe44121d

clonebundles: support for seeding clones from pre-generated bundles Cloning can be an expensive operation for servers because the server generates a bundle from existing repository data at request time. For a large repository like mozilla-central, this consumes 4+ minutes of CPU time on the server. It also results in significant network utilization. Multiplied by hundreds or even thousands of clients and the ensuing load can result in difficulties scaling the Mercurial server. Despite generation of bundles being deterministic until the next changeset is added, the generation of bundles to service a clone request is not cached. Each clone thus performs redundant work. This is wasteful. This patch introduces the "clonebundles" extension and related client-side functionality to help alleviate this deficiency. The client-side feature is behind an experimental flag and is not enabled by default. It works as follows: 1) Server operator generates a bundle and makes it available on a server (likely HTTP). 2) Server operator defines the URL of a bundle file in a .hg/clonebundles.manifest file. 3) Client `hg clone`ing sees the server is advertising bundle URLs. 4) Client fetches and applies the advertised bundle. 5) Client performs equivalent of `hg pull` to fetch changes made since the bundle was created. Essentially, the server performs the expensive work of generating a bundle once and all subsequent clones fetch a static file from somewhere. Scaling static file serving is a much more manageable problem than scaling a Python application like Mercurial. Assuming your repository grows less than 1% per day, the end result is 99+% of CPU and network load from clones is eliminated, allowing Mercurial servers to scale more easily. Serving static files also means data can be transferred to clients as fast as they can consume it, rather than as fast as servers can generate it. This makes clones faster. Mozilla has implemented similar functionality of this patch on hg.mozilla.org using a custom extension. We are hosting bundle files in Amazon S3 and CloudFront (a CDN) and have successfully offloaded >1 TB/day in data transfer from hg.mozilla.org, freeing up significant bandwidth and CPU resources. The positive impact has been stellar and I believe it has proved its value to be included in Mercurial core. I feel it is important for the client-side support to be enabled in core by default because it means that clients will get faster, more reliable clones and will enable server operators to reduce load without requiring any client-side configuration changes (assuming clients are up to date, of course). The scope of this feature is narrowly and specifically tailored to cloning, despite "serve pulls from pre-generated bundles" being a valid and useful feature. I would eventually like for Mercurial servers to support transferring *all* repository data via statically hosted files. You could imagine a server that siphons all pushed data to bundle files and instructs clients to apply a stream of bundles to reconstruct all repository data. This feature, while useful and powerful, is significantly more work to implement because it requires the server component have awareness of discovery and a mapping of which changesets are in which files. Full, clone bundles, by contrast, are much simpler. The wire protocol command is named "clonebundles" instead of something more generic like "staticbundles" to leave the door open for a new, more powerful and more generic server-side component with minimal backwards compatibility implications. The name "bundleclone" is used by Mozilla's extension and would cause problems since there are subtle differences in Mozilla's extension. Mozilla's experience with this idea has taught us that some form of "content negotiation" is required. Not all clients will support all bundle formats or even URLs (advanced TLS requirements, etc). To ensure the highest uptake possible, a server needs to advertise multiple versions of bundles and clients need to be able to choose the most appropriate from that list one. The "attributes" in each server-advertised entry facilitate this filtering and sorting. Their use will become apparent in subsequent patches. Initial inspiration and credit for the idea of cloning from static files belongs to Augie Fackler and his "lookaside clone" extension proof of concept.
author Gregory Szorc <gregory.szorc@gmail.com>
date Fri, 09 Oct 2015 11:22:01 -0700
parents af9d9b778550
children 67a4e42a651f
line wrap: on
line source

from pprint import pprint
from mercurial import minirst

def debugformat(text, form, **kwargs):
    if form == 'html':
        print "html format:"
        out = minirst.format(text, style=form, **kwargs)
    else:
        print "%d column format:" % form
        out = minirst.format(text, width=form, **kwargs)

    print "-" * 70
    if type(out) == tuple:
        print out[0][:-1]
        print "-" * 70
        pprint(out[1])
    else:
        print out[:-1]
    print "-" * 70
    print

def debugformats(title, text, **kwargs):
    print "== %s ==" % title
    debugformat(text, 60, **kwargs)
    debugformat(text, 30, **kwargs)
    debugformat(text, 'html', **kwargs)

paragraphs = """
This is some text in the first paragraph.

  A small indented paragraph.
  It is followed by some lines
  containing random whitespace.
 \n  \n   \nThe third and final paragraph.
"""

debugformats('paragraphs', paragraphs)

definitions = """
A Term
  Definition. The indented
  lines make up the definition.
Another Term
  Another definition. The final line in the
   definition determines the indentation, so
    this will be indented with four spaces.

  A Nested/Indented Term
    Definition.
"""

debugformats('definitions', definitions)

literals = r"""
The fully minimized form is the most
convenient form::

  Hello
    literal
      world

In the partially minimized form a paragraph
simply ends with space-double-colon. ::

  ////////////////////////////////////////
  long un-wrapped line in a literal block
  \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\

::

  This literal block is started with '::',
    the so-called expanded form. The paragraph
      with '::' disappears in the final output.
"""

debugformats('literals', literals)

lists = """
- This is the first list item.

  Second paragraph in the first list item.

- List items need not be separated
  by a blank line.
- And will be rendered without
  one in any case.

We can have indented lists:

  - This is an indented list item

  - Another indented list item::

      - A literal block in the middle
            of an indented list.

      (The above is not a list item since we are in the literal block.)

::

  Literal block with no indentation (apart from
  the two spaces added to all literal blocks).

1. This is an enumerated list (first item).
2. Continuing with the second item.

(1) foo
(2) bar

1) Another
2) List

Line blocks are also a form of list:

| This is the first line.
  The line continues here.
| This is the second line.
"""

debugformats('lists', lists)

options = """
There is support for simple option lists,
but only with long options:

-X, --exclude  filter  an option with a short and long option with an argument
-I, --include          an option with both a short option and a long option
--all                  Output all.
--both                 Output both (this description is
                       quite long).
--long                 Output all day long.

--par                 This option has two paragraphs in its description.
                      This is the first.

                      This is the second.  Blank lines may be omitted between
                      options (as above) or left in (as here).


The next paragraph looks like an option list, but lacks the two-space
marker after the option. It is treated as a normal paragraph:

--foo bar baz
"""

debugformats('options', options)

fields = """
:a: First item.
:ab: Second item. Indentation and wrapping
     is handled automatically.

Next list:

:small: The larger key below triggers full indentation here.
:much too large: This key is big enough to get its own line.
"""

debugformats('fields', fields)

containers = """
Normal output.

.. container:: debug

   Initial debug output.

.. container:: verbose

   Verbose output.

   .. container:: debug

      Debug output.
"""

debugformats('containers (normal)', containers)
debugformats('containers (verbose)', containers, keep=['verbose'])
debugformats('containers (debug)', containers, keep=['debug'])
debugformats('containers (verbose debug)', containers,
            keep=['verbose', 'debug'])

roles = """Please see :hg:`add`."""
debugformats('roles', roles)


sections = """
Title
=====

Section
-------

Subsection
''''''''''

Markup: ``foo`` and :hg:`help`
------------------------------
"""
debugformats('sections', sections)


admonitions = """
.. note::

   This is a note

   - Bullet 1
   - Bullet 2

   .. warning:: This is a warning Second
      input line of warning

.. danger::
   This is danger
"""

debugformats('admonitions', admonitions)

comments = """
Some text.

.. A comment

   .. An indented comment

   Some indented text.

..

Empty comment above
"""

debugformats('comments', comments)


data = [['a', 'b', 'c'],
         ['1', '2', '3'],
         ['foo', 'bar', 'baz this list is very very very long man']]

rst = minirst.maketable(data, 2, True)
table = ''.join(rst)

print table

debugformats('table', table)

data = [['s', 'long', 'line\ngoes on here'],
        ['', 'xy', 'tried to fix here\n        by indenting']]

rst = minirst.maketable(data, 1, False)
table = ''.join(rst)

print table

debugformats('table+nl', table)