Differences between revisions 4 and 14 (spanning 10 versions)

Mirroring infrastructure in PyPI

PEP: xx
Title: Mirroring infrastructure in PyPI
Author: Tarek Ziadé
Discussions-To: Catalog SIG
Status: Draft
Python-Version: 2.6

Abstract

This PEP describes a mirroring infrastructure for PyPI.

Motivations

PyPI is hosting over 4000 projects and is used on a daily basis by people to build applications. Especially systems like easy_install and zc.buildout make intensive usage of PyPI.

For people making intensive use of PyPI, it can act as a single point of failure. People have started to set up some mirrors, both private and public. Those mirrors are active mirrors, which means that they are browsing PyPI to get synced.

In order to make the system more reliable, this PEP describes:

- the mirror listing and registering at PyPI

- the pages a public mirror should maintain.

these pages will be used by PyPI, in order to get hit counts and the last modified date.

- how a mirror should synchronize with PyPI

- how a client can implement a fail-over mechanism

- a contact form for Package maintainers

Mirror listing and registering

A new text page will be added at http://pypi.python.org/mirrors that can be browsed like the simple index. This page gives a list of the mirrors through a list of links.

These links are the URL of the simple index of each mirror. The page will look like this:

# PyPI mirrors
#    
# If you want to register a new mirror, send an email
# to the catalog-SIG@python.org with:
#
# - The urls of your mirror:
#   - the root of the server
#   - the index page 
#   - the last modified page
#   - the local stats page
#   - the global stats page
#   - the mirrors page
#
# - The name and email of the maintainer.
#   
#   The registering is done manually and to become a
#   mirror, you need to strictly follow the mirror protocol
#   described here:
#
#    http://wiki.python.org/PEP_374
#    
# root,index,last-modified,local-stats,stats,mirrors
http://example.com/pypi,index,last-modified,local-stats,stats,mirrors
http://example2.com/pypi,index,last-modified,local-stats,stats,mirrors

When a mirror is proposed on the mailing list, it is manually added in the mirror list in the PyPI application after it has been checked to be compliant with the mirroring rules.

The mirror list page is a simple text page that can be browsed by any tool that wants to get a list of registered mirrors. Other package indexes that are not mirrors of PyPI are not added in the mirror list in PyPI. Although they can provide themselve the same mirroring list mechanism for their own mirrors.

Special pages a mirror needs to provide

A mirror needs to provide four pages, beside the index one:

last-modified
local-stats
stats
mirrors

Last modified date

CPAN uses a freshness date system where the mirror last synchronisation date is made available.

For PyPI, each mirror needs to maintain an url with a simple text content that represents the last synchronisation date the mirror maintains.

The date is provided in GMT time, using the iso 8601 format (http://en.wikipedia.org/wiki/ISO_8601)

Each mirror will be responsible to maintain its last modified date.

Conventionaly, this page should be reachable at: "/last-modified".

Local statistics

Each mirror is responsible to count all the downloads that where done on it. This is used by PyPI to sum up all downloads, to be able to display the grand total.

This page is a csv-like page, with a header at the first line. It needs to obey PEP 305 http://www.python.org/dev/peps/pep-0305/#id19. Basically, it should be readable by Python csv module.

The fields in this file are:

package: the distutils id of the package.
filename: the filename that has been downloaded.
useragent: the User-Agent of the client that has downloaded the package.
count: the number of downloads.

The page will look like this:

# package,filename,useragent,count
zc.buildout,zc.buildout-1.6.0.tgz,MyAgent,142
...

The counting starts the day the mirror is launched.

Conventionaly, this page should be reachable at: "/local-stats", but any url relative to the mirror root can be given.

Statistics page

PyPI and each mirror are responsible to provide the grand total page at "/stats". This page is calculated daily by PyPI, by reading all mirrors local stats and suming them.

Therefore the mirrors should not try to rebuild this stat page but simply get PyPI's one during each synchronization.

It has the same structure than the local-stats page.

Conventionaly, this page should be reachable at: "/stats".

Mirrors listing page

Like /stats, each mirror should get and provide the /mirrors page.

Conventionaly, this page should be reachable at: "/mirrors".

How a mirror should synchronize with PyPI

A mirroring protocol calls Simple Index was described and implemented by Martin v. Loewis and Jim Fulton, based on how easy_install works. This section synthesizes it and give a few relevant links, plus a small part about User-Agent.

The mirroring protocol

XXX changelog, pje link + to be defined

User-agent request header

In order to be able to differentiate actions taken by clients over PyPI, a specific user agent name should be provided by all mirroring softwares.

This is also true for all clients like:

zc.buildout
setuptools
pyinstaller
etc.

XXX user agent registering mechanism at PyPI ?

How a client can use PyPI and its mirrors

XXX

Fail-over mechanism

Clients that are browsing PyPI should be able to use a fail-over mechanism when PyPI is not responding.

This can be done by parsing the /mirrors page of PyPI or the one located on any PyPI mirror.

It is up to the client to decide wich mirror should be used, depending on its geographical location and its responsivness.

This PEP does not describe how this fail-over mechanism should work, but it is strongly encouraged that the clients try to use the nearest mirror.

The clients so far that could use this mechanism:

setuptools
zc.buildout (through setuptools)
pyinstaller

Extra package indexes

It is obvious that some package will not be uploaded to PyPI. Wether because they are private or wether because the project maintainer runs his own server where people get the project package. Although, it is strongly encouraged that a public package index follows PyPI and distutils protocols. In other words, the "register" and "upload" command should be compatible with any package index server out there.

Softwares that are compatible with PyPI and distutils:

Merging several indexes

When a client needs to get some packages from several distinct indexes, it should be able to use each one of them as a potential source of packages. Different indexes should be defined as a sorted list for the client to look for a package.

Each independant index can of course provide a list of its mirrors, if the /mirrors page is available.

That permits all combinations at client level, for a reliable packaging system with all levels of privacy.

Other PyPI enhancements

XXX

Contact form for Package maintainers

A form reachable from the package page will be added, where a registered user can submit a message to the package owner. This is to be used when someone wants to take over the distutils id name, or when someone (like a packager for example) would like to reach the package owner for some questions.

XXX isn't the mail in the metadata enough ? XXX the original whish here was to enforce the package owner to upload sdist.

-  ⇤ ← Revision 4 as of 2008-10-12 16:01:58 → 
  Size: 3846
  Editor: tarek
  Comment:
+   ← Revision 14 as of 2009-02-15 11:31:25 → ⇥
  Size: 7971
  Editor: tarek
  Comment:
-Deletions are marked like this.
+Additions are marked like this.
 Line 1:
+## page was renamed from PEP 374
-Line 3:
+Line 4:
- * PEP: 374
+ * PEP: xx
-Line 14:
+Line 15:
-== Motivation ==
+== Motivations ==
-Line 18:
+Line 19:
-and Buildout make intensive usage of PyPI.

For people making extensive use of PyPI, it can act as a single point
+and zc.buildout make intensive usage of PyPI.

For people making intensive use of PyPI, it can act as a single point
-Line 24:
+Line 25:
-  The motivation of this PEP is to set up a registering 
mechanism in PyPI in order to list all the public PyPI mirrors
and to provide an event based system where all mirrors get 
informed via RPC when a package has been uploaded, modified,
or removed, so they can eventually sync themselves.

This PEP describes:

 * Mirror listing and registering  
 * Ping mechanism
+In order to make the system more reliable, this PEP describes:

- the mirror listing and registering at PyPI 

- the pages a public mirror should maintain. 
  these pages will be used by PyPI, in order to get 
  hit counts and the last modified date.

- how a mirror should synchronize with PyPI

- how a client can implement a fail-over mechanism

- a contact form for Package maintainers
-Line 38:
+Line 42:
-A new HTML page will be added at http://pypi.python.org/mirrors
+A new text page will be added at http://pypi.python.org/mirrors
-Line 46:
+Line 50:
-<html>
  <head><title>PyPI mirrors</title></head>
  <body>
  
    <h1>PyPI mirrors</h1>
    
    <p>
    If you want to register a new mirror, send an email
    to the catalog-SIG@python.org with:
    </p>

    <ol>
        <li> The url of your mirror.</li>
        <li> The name and email of the maintainer.</li>
    </ol>

    <p>
    The registering is done manually and to become a
    mirror, you need to strictly follow the package index
    API defined here:
    </p>
    
    <p>
    http://peak.telecommunity.com/DevCenter/EasyInstall#package-index-api
    </p>
    
    <ul id="mirror-links">
        <li>
          <a class="mirrorLink" href="http://example.com/pypi">Mirror #1</a> |
          <a class="mirrorPage" href="http://pypi.python.org/mirrors/1">more infos</a>
        </li>
    </ul>

  </body>
</html>
+# PyPI mirrors
#    
# If you want to register a new mirror, send an email
# to the catalog-SIG@python.org with:
#
# - The urls of your mirror:
#   - the root of the server
#   - the index page 
#   - the last modified page
#   - the local stats page
#   - the global stats page
#   - the mirrors page
#
# - The name and email of the maintainer.
#   
#   The registering is done manually and to become a
#   mirror, you need to strictly follow the mirror protocol
#   described here:
#
#    http://wiki.python.org/PEP_374
#    
# root,index,last-modified,local-stats,stats,mirrors
http://example.com/pypi,index,last-modified,local-stats,stats,mirrors
http://example2.com/pypi,index,last-modified,local-stats,stats,mirrors
-Line 84:
+Line 77:
-added in a dedicated SQL table in the PyPI application.

The mirror list page is a simple html page that can be browsed
+added in the mirror list in the PyPI application after it
has been checked to be compliant with the mirroring rules.

The mirror list page is a simple text page that can be browsed
-Line 88:
+Line 82:
-Each mirror gets its own page url at PyPI with extra information.
The name of that page is the ID of the mirror in the PyPI system.

This page contains extra information about the mirror, like its freshness
date:
+Other package indexes that are not mirrors of PyPI are not added in the 
mirror list in PyPI. Although they can provide themselve the 
same mirroring list mechanism for their own mirrors.

== Special pages a mirror needs to provide ==

A mirror needs to provide four pages, beside the index one:

 * last-modified
 * local-stats
 * stats
 * mirrors
 
=== Last modified date ===

CPAN uses a freshness date system where the mirror last synchronisation 
date is made available.

For PyPI, each mirror needs to maintain an url with a simple text content
that represents the last synchronisation date the mirror maintains.

The date is provided in GMT time, using the iso 8601 format
(http://en.wikipedia.org/wiki/ISO_8601)

Each mirror will be responsible to maintain its last modified date. 

Conventionaly, this page should be reachable at: "/last-modified".

=== Local statistics ===

Each mirror is responsible to count all the downloads
that where done on it. This is used by PyPI to sum up all
downloads, to be able to display the grand total.

This page is a csv-like page, with a header at the first 
line. It needs to obey PEP 305 http://www.python.org/dev/peps/pep-0305/#id19.
Basically, it should be readable by Python csv module.

The fields in this file are:

 * package: the distutils id of the package.
 * filename: the filename that has been downloaded.
 * useragent: the User-Agent of the client that has downloaded the package.
 * count: the number of downloads.

The page will look like this:
-Line 96:
+Line 130:
-<html>
  <head><title>PyPI mirror</title></head>
  <body>
  
    <h1>PyPI mirror Mirror #1</h1>
    
    <div>Freshness data: <span id="freshness">Sun May 20 15:23:01 2007</span></div>
  </body>
</html>
+# package,filename,useragent,count
zc.buildout,zc.buildout-1.6.0.tgz,MyAgent,142
...
-Line 109:
+Line 135:
-Other package indexes that are not mirrors of PyPI are not added in the 
mirror list in PyPI.

Although they can provide theirselve the same mirroring list mechanism 
for their own mirrors.

== Freshness date ==

CPAN uses a freshness date system where the mirror last synchronisation date is made available.

For PyPI, the 'last-modified' header can be added in the root page of the index.

Other mirrors can also maintain this header.


== Costs ==

Someone has to manage the list of mirrors. This work should
not take too much time. I am willing to be that maintainer if 
the people that maintain the server don't have the time, or
don't trust me.

== Implementation ==
+The counting starts the day the mirror is launched.

Conventionaly, this page should be reachable at: "/local-stats", but any url relative to the mirror root can be given.

=== Statistics page ===

PyPI and each mirror are responsible to provide the grand total
page at "/stats". This page is calculated daily by PyPI,
by reading all mirrors local stats and suming them. 

Therefore the mirrors should not try to rebuild this stat page but simply
get PyPI's one during each synchronization.

It has the same structure than the local-stats page.

Conventionaly, this page should be reachable at: "/stats".

=== Mirrors listing page ===

Like /stats, each mirror should get and provide the /mirrors
page.

Conventionaly, this page should be reachable at: "/mirrors".

== How a mirror should synchronize with PyPI ==

A mirroring protocol calls Simple Index was described 
and implemented by Martin v. Loewis and Jim Fulton, based on 
how easy_install works. This section synthesizes it
and give a few relevant links, plus a small part about 
User-Agent.

=== The mirroring protocol ===

XXX changelog, pje link + to be defined

=== User-agent request header ===

In order to be able to differentiate actions taken by clients
over PyPI, a specific user agent name should be provided by all 
mirroring softwares.

This is also true for all clients like:

 * zc.buildout
 * setuptools
 * pyinstaller
 * etc.

XXX user agent registering mechanism at PyPI ?

== How a client can use PyPI and its mirrors ==
-Line 136:
+Line 190:
-== Third-party applications ==

A sample module will be written and published to demonstrate how a mirror 
can implement the XML-RPC APIs in Python.
+== Fail-over mechanism ==

Clients that are browsing PyPI should be able to use 
a fail-over mechanism when PyPI is not responding.

This can be done by parsing the /mirrors page of PyPI
or the one located on any PyPI mirror. 

It is up to the client to decide wich mirror should
be used, depending on its geographical location and
its responsivness.

This PEP does not describe how this fail-over
mechanism should work, but it is strongly encouraged
that the clients try to use the nearest mirror.

The clients so far that could use this mechanism:

 * setuptools
 * zc.buildout (through setuptools)
 * pyinstaller

== Extra package indexes ==

It is obvious that some package will not be uploaded
to PyPI. Wether because they are private or wether because
the project maintainer runs his own server where people
get the project package. Although, it is strongly
encouraged that a public package index follows PyPI
and distutils protocols. In other words, the "register"
and "upload" command should be compatible with any 
package index server out there.

Softwares that are compatible with PyPI and distutils:

 * PloneSoftwareCenter
 * EggBasket

== Merging several indexes ==

When a client needs to get some packages from several 
distinct indexes, it should be able to use each one of them
as a potential source of packages. Different indexes
should be defined as a sorted list for the client to
look for a package.

Each independant index can of course provide a list of 
its mirrors, if the /mirrors page is available.

That permits all combinations at client level, for a reliable
packaging system with all levels of privacy.

== Other PyPI enhancements ==

XXX

=== Contact form for Package maintainers ===

A form reachable from the package page will be added,
where a registered user can submit a message to the package
owner. This is to be used when someone wants to take over
the distutils id name, or when someone (like a packager
for example) would like to reach the package owner 
for some questions.

XXX isn't the mail in the metadata enough ?
XXX the original whish here was to enforce the package owner
to upload sdist.