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Thursday, August 11 2016

Back from Flock 2016

Flock is always a peculiar time of the year for me. For one it is one of the few time I get to meet with my colleagues but more than that, it's also one of the few time I get to spend a few days with fellows from this Fedora community that is so dear to me.

I have to say that this year was no exception. Flock 2016 has been really nice. I can, of course, only speak for myself, but from what I have seen we got a lot of work done and we are now ready to move forward on quite a few subjects.

One of the most important aspect of flock is the fact that an important part of the community gathers in one place, but we need to be careful as the conference only represent about 10% of all the Fedora contributors. So it is our duty as attendee to report to the broader community about the subjects that were discussed and the talks we have had.

It is of course practically impossible to mention everything here, for one because I took very little note during the conference, but I would like to point out the topics that appeared the most important to me during that conference.

Fedora at large and its community

During the opening keynote, mattdm gave an overview of how Fedora is appreciated outside of our community. It seems that Fedora 24 has been doing great, same for Fedora 23 before that. The IT world seems to appreciate the Fedora.next program we have started and what it is leading to.

Matt also gave a few numbers on the side of our community and our contributor base. These were numbers that had already been presented in his talk at DevConf 2016 (talk that I watched on youtube). So there were really new to me, but I still like the fact that there is about 66% of our community that is not working for our primary sponsor, Red Hat. This is healthy for our community, this diversity ensures that we are not just an echo chamber and that it is not just us liking what we do.

The Fedora Infrastructure

This is a part of the project that I am directly involved in and that I think made some really good progress during these few days. We had a few session. It started with a presentation from Kevin and I about the state of the Fedora Infrastructure. We went a little bit through the changes that happened in the last year and ones planned in the coming year, both from an infrastructure and an application point of view.

This has lead a few questions and discussions, all in a nice atmosphere. I had one comment on the presentation that we have not included as much numbers in it as we had last year making it a little harder for people not accustomed with our work to follow. Something to work on for next year.

We also had a workshop session. Over two hours we went through the changes we want to make to the infrastructure (opening our private cloud to our contributors, start investigate where and how to use docker, reflect the level of support provided to services by using different domain names for examples) and for each of these we came to some agreement and made a plan on how to move forward with it.

I will not go to much in the details of what we discussed and what agreement we reached in this blog post as it has already been summarized on the fedora infrastructure list.

Fedora Docker Layered Images

So this an project that has been worked on for a few months now by Adam Miller in coordination with the rel-eng team. The idea is to allow Fedora to start distributing more than just RPMs and in this case, Docker images.

This service is about to land. There are still a few aspect to be worked on, including how to distribute the images to the mirrors and how to ensure users are being redirected to a mirror that is up to date. Dennis, Randy and I had a very interesting discussion around the work that remains to be done for this. It will imply making changes to MirrorManager and likely all of its three components (MirrorManager, MirrorList and the backend services). It might also imply work on the docker side.

Being able to have these discussion while seating on comfortable harmchairs facing each other was really nice. We managed to have a list of applications that needs to be adjusted and a good idea of how the different pieces will work together.

Fedora atomic on a workstation

Patrick gave a very interesting presentation on how he builds and uses Fedora atomic to run it on its laptop. This was really most interesting but it gave a little bit of mixed feelings. On the one side, it looks really promising and exciting to work with, on the other side it seems not really user-friendly and a little hard/time-consuming. I do wonder if, some aspects could not be simplified for me (for example retrieving the list of RPMs currently installed on my machine to insert in the kickstart file instead of more or less starting from scratch).

Maybe I will try to make a little time available this year to try to play with this, it is really tempting.

Automation

Ralph has lead a very nice workshop on automation whose idea was to brainstorm around what we do and that we could automate and what we all have built script to do for us and which thus may need to be generalized.

The discussion has been lively and quite a few ideas were exchanged.

Two of them sticked with me a little more

  • Generate a cron job gathering information from pkgdb, koji, bodhi, fedocal to

give access at a single location about releases. What are they koji tags? What are their bodhi name? What are their current status (released? beta-freeze? beta released? alpha?...)? There are a few applications relying on this information and while a good part of it is present in pkgdb, not all is and it does not necessarily make sense to add it there.

  • Create some sort of service that triggers builds upon git push and even the

creation of bodhi update if we want. There are quite a few use-case that people would like to see supported and some people do not want this at all, so this should be entirely opt-in. Currently is idea is to ask packager to place a ChangeLog file in their git repo, next to the spec and the sources files and place in this file the information needed to create the bodhi update. If in a push, this ChangeLog file is updated, automatically trigger the build in koji and if it finished successfully, create the update in bodhi. That means that: without this ChangeLog file, nothing changes from the current situation, if the ChangeLog is not touched, nothing changes from the current situation, if the ChangeLog file is touched but the build fails in koji, the only change from the current situation is that this service will have saved the user from triggering the build manually.

These were the two ideas that stick with me the most. There has been more discussed and there are more possibilities (like making the service something that is ran locally by the user, as opposed to something ran in the infrastructure).

Pagure

Pagure has been a really nice surprise to me. Many people talked to me about it most often in good terms and sometime with some interesting ideas. I am not sure all the ideas provided will be implemented but there is food for thoughts and enough to keep me busy a little while!

Modularity

I had been following the modularity working group from a little far and I have been quite happy to discuss directly with the people working on this about the work they are trying to achieve.

Ralph and I have had a few lengthy discussion around the life-cycle of packages in this new model and, among others, the impact this would have on tools such as pkgdb. It seems clear to me that while the data model might not necessarily change that much, we will need to adjust pkgdb for this new distribution model. All the details are still not entirely clear, some features will need to be added, the UI will need to be adjusted, overall probably not enough to worth a rewrite of pkgdb but still enough that I will need to spend some cycles on it.

The work done by the modularity group is quite fascinating, I have been involved or the spectator of some the discussion they had and there is really quite a lot of work still to be done and this is sounding really interesting.

If you have not had a chance to see what they are doing, I encourage you to check out their wiki page and check Langdon's presentation at flock as soon as it is available on youtube.

Hubs

Fedora-hubs is a cool project aiming at simplifying the steps new contributors need to take to reach the old contributors. IRC, mailing lists, tickets are all places where activities happen but that might be obscure to new contributors. fedora-hubs tries to fill this gap by aggregating all the activity around a group of people and provide it to new contributors so they know where to look to get aboard.

We ran a workshop with a nice demo at flock. We received some good positive feedbacks and people seem to like how things are looking. Personally flock has also been the occasion to pass the torch on this project. I have been leading it since Ralph changed team but I am really not the expert in the technologies needed for hubs' frontend. So I passed on the torch to Sayan who is much more experienced than I am and who I'm sure will do a great job leading hubs. I will still be around, I am very much interested in helping with backend bits and pieces. FMN still needs some work and a few other applications that I maintain might require adjustments to integrate with hubs the way we want it. So, do expect me around :)

Zanata

Finally, flock has also been the occasion for me to meet up with the folks from zanata (the platform used by fedora's translators). We exchanged a few emails before the conference as we asked them to expand on their web-hooks so we could gather some more stats and include them on fedora-hubs. It was really nice to be able to discuss with them regarding their plans and ours and how we may be able to help each other.

Final words

Well, this has been quite a lengthy blog post, if you made it so far : congratulations!

As a final note, I would like to thank all the organizers of the conference, having tried to place a bid for this year, I have a small idea of the amount of work involved but they managed wonderfully and it was an excellent flock!

Wednesday, June 29 2016

Profiling in python

When working on FMN's new architecture I been wanted to profile a little bit the application, to see where it spends most of its time.

I knew about the classic cProfile builtin in python but it didn't quite fit my needs since I wanted to profile a very specific part of my code, preferrably without refactoring it in such a way that I could use cProfile.

Searching for a solution using cProfile (or something else), I ran into the pycon presentation of A. Jesse Jiryu Davis entitled 'Python performance profiling: The guts and the glory'. It is really quite an interesting talk and if you have not seen it, I would encourage you to watch it (on youtube)

In this talk is presented yappi, standing for Yet Another Python Profiling Implementation and writen by Sümer Cip, together with some code allowing to easy use it and write the output in a format compatible with callgrind (allowing us to use KCacheGrind to visualize the results).

To give you an example, this is how it looked before (without profiling):

t = time.time()
results = fmn.lib.recipients(PREFS, msg, valid_paths, CONFIG)
log.debug("results retrieved in: %0.2fs", time.time() - t)

And this is the same code, integrated with yappi

import yappi
yappi.set_clock_type('cpu')
t = time.time()
yappi.start(builtins=True)
results = fmn.lib.recipients(PREFS, msg, valid_paths, CONFIG)
stats = yappi.get_func_stats()
stats.save('output_callgrind.out', type='callgrind')
log.debug("results retrieved in: %0.2fs", time.time() - t)

As you can see, all it takes is 5 lines of code to profile the function fmn.lib.recipients and dump the stats in a callgrind format.

And this is how the output looks like in KCacheGrind :) kcachegrind_fmn.png

Saturday, June 25 2016

New FMN architecture and tests

New FMN architecture and tests

Introduction

FMN is the FedMsg Notification service. It allows any contributors (or actually, anyone with a FAS account) to tune what notification they want to receive and how.

For example it allows saying things like:

  • Send me a notification on IRC for every package I maintain that has successfully built on koji
  • Send me a notification by email for every request made in pkgdb to a package I maintain
  • Send me a notification by IRC when a new version of a package I maintain is found

How it works

The principile is that anyone can log in on the web UI of FMN there, they can create filters on a specific backend (email or IRC mainly) and add rules to that filter. These rules must either be validated or invalited for the notification to be sent.

Then the FMN backend listens to all the messages sent on Fedora's fedmsg and for each message received, goes through all the rules in all the filters to figure out who wants to be notified about this action and how.

The challenge

Today, computing who wants to be notified and how takes about 6 seconds to 12 seconds per message and is really CPU intensive. This means that when we have an operation sending a few thousands messages on the bus (for example, mass-branching or a packager maintaining a lot of packages orphaning them), the queue of messages goes up and it can take hours to days for a notification to be delivered which could be problematic in some cases.

The architecture

This is the current architecture of FMN:

|                        +--------\
|                   read |  prefs | write
|                  +---->|  DB    |<--------+
|                  |     \--------+         |
|        +-----+---+---+            +---+---+---+---+   +----+
|        |     |fmn.lib|            |   |fmn.lib|   |   |user|
v        |     +-------+            |   +-------+   |   +--+-+
fedmsg+->|consumer     |            |central webapp |<-----+
+        +-----+  +---+|            +---------------+
|        |email|  |irc||
|        +-+---+--+-+-++
|          |        |
|          |        |
v          v        v

As you can see it is not clear where the CPU intensive part is and that's because it is in fact integrated in the fedmsg consumer. This design, while making things easier brings the downside of making it pratically impossible to scale it easily when we have an event producing lots of messages. We multi-threaded the application as much as we could, but we were quickly reaching the limit of the GIL.

To try improving on this situation, we reworked the architecture of the backend as follow:

                                                     +-------------+
                                              Read   |             |   Write
                                              +------+  prefs DB   +<------+
                                              |      |             |       |
   +                                          |      +-------------+       |
   |                                          |                            |   +------------------+   +--------+
   |                                          |                            |   |    |fmn.lib|     |   |        |
   |                                          v                            |   |    +-------+     |<--+  User  |
   |                                    +----------+                       +---+                  |   |        |
   |                                    |   fmn.lib|                           |  Central WebApp  |   +--------+
   |                                    |          |                           +------------------+
   |                             +----->|  Worker  +--------+
   |                             |      |          |        |
fedmsg                           |      +----------+        |
   |                             |                          |
   |                             |      +----------+        |
   |   +------------------+      |      |   fmn.lib|        |       +--------------------+
   |   | fedmsg consumer  |      |      |          |        |       | Backend            |
   +-->|                  +------------>|  Worker  +--------------->|                    |
   |   |                  |      |      |          |        |       +-----+   +---+  +---+
   |   +------------------+      |      +----------+        |       |email|   |IRC|  |SSE|
   |                             |                          |       +--+--+---+-+-+--+-+-+
   |                             |      +----------+        |          |        |      |
   |                             |      |   fmn.lib|        |          |        |      |
   |                             |      |          |        |          |        |      |
   |                             +----->|  Worker  +--------+          |        |      |
   |                         RabbitMQ   |          |    RabbitMQ       |        |      |
   |                                    +----------+                   |        |      |
   |                                                                   v        v      v
   |
   |
   |
   v

The idea is that the fedmsg consumer listens to Fedora's fedmsg, put the messages in a queue. These messages are then picked from the queue by multiple workers who will do the CPU intensive task and put their results in another queue. The results are then picked from this second queue by a backend process that will do the actually notification (sending the email, the IRC message).

We also included an SSE component to the backend, which is something we want to do for fedora-hubs but this still needs to be written.

Testing the new architecture

The new architecture looks fine on paper, but one would wonder how it performs in real-life and with real data.

In order to test it, we wrote two scripts (one for the current architecture and one for the new) sending messages via fedmsg or putting in messages in the queue that the workers listens to, therefore mimiking there the behavior of the fedmsg consumer. Then we ran different tests.

The machine

The machine on which the tests were run is:

  • CPU: Intel i5 760 @ 2.8GHz (quad-core)
  • RAM: 16G DDR2 (1333 Mhz)
  • Disk: ScanDisk SDSSDA12 (120G)
  • OS: RHEL 7.2, up to date
  • Dataset: 15,000 (15K) messages

The results

The current architecture

The current architecture only allows to run one test, send 15K fedmsg messages and let the fedmsg consumer process them and monitor how long it takes to digest them.

Test #0 - fedmsg based
  Lasted for 9:05:23.313368
  Maxed at:  14995
  Avg processing: 0.458672376874 msg/s

The new architecture

The new architecture being able to scale we performed a different tests with it, using 2 workers, then 4 workers, then 6 workers and finally 8 workers. This gives us an idea if the scaling is linear or not and how much improvement we get by adding more workers.

Test #1 - 2 workers - 1 backend
  Lasted for 4:32:48.870010
  Maxed at:  13470
  Avg processing: 0.824487297215 msg/s
Test #2 - 4 workers - 1 backend
  Lasted for 3:18:10.030542
  Maxed at:  13447
  Avg processing: 1.1342276217 msg/s
Test #3 - 6 workers - 1 backend
  Lasted for 3:06:02.881912
  Maxed at:  13392
  Avg processing: 1.20500359971 msg/s
Test #4 - 8 workers - 1 backend
  Lasted for 3:14:11.669631
  Maxed at:  13351
  Avg processing: 1.15160928467 msg/s

Conclusions

Looking at the results of the tests, the new architecture is clearly handling its load better and faster. However, the progress aren't as linear as we like. My feeling is that retrieve information from the cache (here redis) is at one point getting slower, eventually also because of the central lock we tell redis to use.

As time permits, I will try to investigate this further to see if we can still gain some speed.

Monday, May 9 2016

Playing with FMN

On Friday, I have been started to play with FMN

Currently, there is a fedmsg consumer that listens to the messages coming from all over the Fedora infrastructure, then based on the preferences set in FMN's web UI it decides whether to send a notification and how.

There has been thoughts on reworking the process to allow splitting it over multiple nodes.

The idea is to do something like this:


                                +-> worker -+          these senders
                                |           |          just do simple I/O
                                |           |
                                +-> worker -+          +-> email sender
                                |           |          |
                                |           |          |
fedmsg -> fmn consumer -> redis +-> worker -+-> redis -+-> IRC sender
                                |           |          |
                                |           |          |
                                +-> worker -+          +-> GCM sender
                                |           |
                                |           |
                                +-> worker -+

My question was how to divide the message coming among the different worker. So I adjusted the consumer a little to forward each message received to a different redis channel.

The code looks something like:

            i = random.randint(0, self.workers-1)
            log.debug('Sending to worker %s' % i)
            print(self.redis[i])
            self.redis[i].publish('%s' % i, json.dumps(raw_msg))

We're randomly picking one of the worker from the N workers we know are available (for my tests: 4).

Sounds simple enough right? But will it spread the load between the workers evenly?

So over the week-end I left my test program running.

This is the output collected:

  • worker 0: 126468 messages received
  • worker 1: 126908 messages received
  • worker 2: 126993 messages received
  • worker 3: 126372 messages received

This makes a total of 506741 messages received over the week-end and the load is spread among the workers as such:

  • worker 0: 24.95713% of the messages
  • worker 1: 25.04396% of the messages
  • worker 2: 25.06073% of the messages
  • worker 3: 24.93818% of the messages

Looks good enough :)

Next step, splitting the code between fmn.consumer, fmn.worker and fmn.backend (the one doing the IO) and figuring out how to deal with the cache.

Wednesday, March 2 2016

Monitor performances of WSGI apps

Accessing pagure's performances via mod_wsgi-express

Continue reading...

Tuesday, January 5 2016

Setting up pagure on a banana pi

This is a small blog post about setting up pagure on a banana pi.

Continue reading...

Friday, December 11 2015

Testing distgit in staging with fedpkgstg

Every once in a while we make changes to dist-git in the Fedora infrastructure. This means, we need to test our changes to make sure they do not break (ideally, at all).

These days, we are working on adding namespacing to our git repos so that we can support delivering something else than rpms (the first use-case being, docker). So with the current set-up we have, we added namespacing to pkgdb which remains our main endpoint to manage who has access to which git repo (pkgdb being in a way a glorified interface to manage our gitolite). The next step there is to teach gitolite about this namespacing.

The idea is to move from:

 /srv/git/repositories/<pkg1>.git
 /srv/git/repositories/<pkg2>.git
 /srv/git/repositories/<pkg3>.git
 /srv/git/repositories/<pkg4>.git

To something like:

 /srv/git/repositories/rpms/<pkg1>.git
 /srv/git/repositories/rpms/<pkg2>.git
 /srv/git/repositories/rpms/<pkg3>.git
 /srv/git/repositories/rpms/<pkg4>.git
 /srv/git/repositories/docker/<pkg2>.git
 /srv/git/repositories/docker/<pkg5>.git

But, in order to keep things working with the current clone out there, we'll symlink the rpms namespace to one level higher in the hierarchy which should basically keep things running as they are currently.

So the question at hand is, now that we have adjusted our staging pkgdb and dist-git, how do we test that fedpkg still works.

This is a recipe from bochecha to make it easy to test fedpkg in staging while not breaking it for regular use.

It goes in three steps:

1. Edit the file /etc/rpkg/fedpkg.conf and add to it:

[fedpkgstg]
lookaside = http://pkgs.stg.fedoraproject.org/repo/pkgs
lookasidehash = md5
lookaside_cgi = https://pkgs.stg.fedoraproject.org/repo/pkgs/upload.cgi
gitbaseurl = ssh://%(user)s@pkgs.stg.fedoraproject.org/%(module)s
anongiturl = git://pkgs.stg.fedoraproject.org/%(module)s
tracbaseurl = https://%(user)s:%(password)s@fedorahosted.org/rel-eng/login/xmlrpc
branchre = f\d$|f\d\d$|el\d$|olpc\d$|master$
kojiconfig = /etc/koji.conf
build_client = koji

2. Create a fedpkgstg (the name of the cli must be the same as the title of the section entered in the config file above)

sudo ln -s /usr/bin/fedpkg /usr/bin/fedpkgstg

3. call fedpkgstg to test staging and fedpkg to do your regular operation against the production instances



Thanks bochecha!

Thursday, November 19 2015

Introducing mdapi

I have recently been working on a new small project, an API to query the information stored in the meta-data present in the RPM repositories (Fedora's and EPEL's).

These meta-data include, package name, summary, description, epoch, version, release but also changelog, the list of all the files in a package. It also includes the dependencies information, the regular Provides, Requires, Obsoletes and Conflicts but also the new ones for soft-dependencies: Recommends, Suggests, Supplements and Enhances.

With this project, we are exposing all this information to everyone, in an easy way.

mdapi will check if the package asked is present in either of the updates-testing, updates or release repositories (in this order) and it will return the information found in the first repo where there is a match (and say so) So for example: https://apps.fedoraproject.org/mdapi/f23/pkg/guake?pretty=True*

shows the package information for guake in Fedora 23, where guake has been updated but the latest version is in updates not updates-testing. Therefore it says "repo": "updates".

The application is written entirely in python3 using aiohttp which is itself based on asyncio, allowing it to handle some load very nicely.

Just to show you, here is the result of a little test performed with the apache benchmark tool:

    $ ab -c 100 -n 1000 https://apps.fedoraproject.org/mdapi/f23/pkg/guake
    This is ApacheBench, Version 2.3 <$Revision: 1663405 $>
    Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
    Licensed to The Apache Software Foundation, http://www.apache.org/
    
    Benchmarking apps.fedoraproject.org (be patient)
    Completed 100 requests
    Completed 200 requests
    Completed 300 requests
    Completed 400 requests
    Completed 500 requests
    Completed 600 requests
    Completed 700 requests
    Completed 800 requests
    Completed 900 requests
    Completed 1000 requests
    Finished 1000 requests
    
    
    Server Software:        Python/3.4
    Server Hostname:        apps.fedoraproject.org
    Server Port:            443
    SSL/TLS Protocol:       TLSv1.2,ECDHE-RSA-AES128-GCM-SHA256,4096,128
    
    Document Path:          /mdapi/f23/pkg/guake
    Document Length:        1843 bytes
    
    Concurrency Level:      100
    Time taken for tests:   41.825 seconds
    Complete requests:      1000
    Failed requests:        0
    Total transferred:      2133965 bytes
    HTML transferred:       1843000 bytes
    Requests per second:    23.91 [#/sec] (mean)
    Time per request:       4182.511 [ms] (mean)
    Time per request:       41.825 [ms] (mean, across all concurrent requests)
    Transfer rate:          49.83 [Kbytes/sec] received
    
    Connection Times (ms)
                  min  mean[+/-sd] median   max
    Connect:      513  610 207.1    547    1898
    Processing:   227 3356 623.2   3534    4025
    Waiting:      227 3355 623.2   3533    4024
    Total:        781 3966 553.2   4085    5377
    
    Percentage of the requests served within a certain time (ms)
      50%   4085
      66%   4110
      75%   4132
      80%   4159
      90%   4217
      95%   4402
      98%   4444
      99%   4615
     100%   5377 (longest request)

Note the:

    Time per request:       41.825 [ms] (mean, across all concurrent requests)

We are below 42ms so (0.042 second) to retrieve the info of a package in the updates repo and that's while executing 100 requests at the same time on a server that is in the US while I am in Europe.




  • Note the ?pretty=True in the URL, this is something handy to view the JSON

returned but I advise against using it in your applications as it will increase the amount of data returned and thus slow things down.

Note2: Your mileage may vary when testing mdapi yourself, but it should remain pretty fast!

Wednesday, August 5 2015

Faitout changes home

Faitout is an application giving you full access to a postgresql database for 30 minutes.

This is really handy to run tests against.

For example, for some of my applications, I run the tests locally against a in-memory sqlite database (very fast) and when I push, the tests are ran on jenkins but this time using faitout (a little slower, but much closer to the production environment). This setup allows me to find early potential error in the code that sqlite does not trigger.

Faitout is running the cloud of the Fedora infrastructure and since this cloud has just been rebuilt, we had to move it. While doing so, faitout got a nice new address:

http://faitout.fedorainfracloud.org/

So if you are using it, don't forget to update your URL ;-)



See also: Previous blog posts about faitout

Thursday, July 23 2015

Introducing flask-multistatic

flask is a micro-web-framework in python. I have been using it for different projects for a couple of years now and I am quite happy with it.

I have been using it for some of the applications ran by the Fedora Infrastructure. Some of these applications could be re-used outside Fedora and this is of course something I would like to encourage.

One of the problem currently is that all those apps are branded for Fedora, so re-using them elsewhere can become complicated, this can be solved by theming. Theming means adjusting two components: templates and static files (images, css...).

Adjusting templates

jinja2 the template engine in flask already supports loading templates from two different directories. This allows to ask the application to load your own template first and if it does not find them, then it looks for it in the directory of the default theme.

Code wise it could look like this:

    # Use the templates
    # First we test the core templates directory
    # (contains stuff that users won't see)
    # Then we use the configured template directory
    import jinja2
    templ_loaders = []
    templ_loaders.append(APP.jinja_loader)
    # First load the templates from the THEME_FOLDER defined in the configuration
    templ_loaders.append(jinja2.FileSystemLoader(os.path.join(
        APP.root_path, APP.template_folder, APP.config['THEME_FOLDER'])))
    # Then load the other templates from the `default` theme folder
    templ_loaders.append(jinja2.FileSystemLoader(os.path.join(
        APP.root_path, APP.template_folder, 'default')))
    APP.jinja_loader = jinja2.ChoiceLoader(templ_loaders)
Adjusting static files

This is a little more tricky as static files are not templates and there is no logic in flask to allow overriding one or another depending on where it is located.

To solve this challenge, I wrote a small flask extension: flask-multistatic that basically allows flask to have the same behavior for static files as it does for templates.

Getting it to work is easy, at the top of your flask application do the imports:

    import flask
    from flask_multistatic import MultiStaticFlask

And make your flask flask application multistatic

    APP = flask.Flask(__name__)
    APP = MultiStaticFlask(APP)

You can then specify multiple folders where static files are located, for example:

    APP.static_folder = [
        os.path.join(APP.root_path, 'static', APP.config['THEME_FOLDER']),
        os.path.join(APP.root_path, 'static', 'default')
    ]

Note: The order the the folder matters, the last one should be the folder with all the usual files (ie: the default theme), the other ones are the folders for your specific theme(s).


Patrick Uiterwijk pointed to me that this method, although working is not ideal for production as it means that all the static files are served by the application instead of being served by the web-server. He therefore contributed an example apache configuration allowing to obtain the same behavior (override static files) but this time directly in apache!



So using flask-multistatic I will finally be able to make my apps entirely theme-able, allowing other projects to re-use them under their own brand.

Monday, June 29 2015

FESCo vote history

A while back I gathered some numbers about the number of participants to some election held in Fedora.

With the results of the new FESCo election being announced I wanted to go back and see the new trend:

            FESCo (voters)
   2008-07    150
   2008-12    169
   2009-06    308
   2009-12    216
   2010-05    180
   2010-11    240
   2011-06    200
   2011-12    225
   2012-06    236
   2012-12    206
   2013-06    166
   2014-02    265
   2014-07    195
   2015-01    283
   2015-06     90

Graphically: 20150629_fesco_voters.png

As you can see, this last election was the one with the lowest number of participants since at least July 2008.

Friday, June 26 2015

Packagers AFK in pkgdb

I just wanted to point out a small feature added to pkgdb recently.

Basically, it integrates with the vacation calendar of fedocal to show on the packager's info page if the person is on vacations or not.

If you are dealing with someone who is slow to answer on bugs, irc or emails, it may give you an insight as to why that is.

pkgdb_vacations2.png



Note: I am in no way saying that Paul is slow to answer bugs, irc or email, and have merely used him to illustrate my thoughts following up on his post about the Red Hat summit and I shall not be held responsible for any variations in Paul's response time :-)

Thursday, June 25 2015

EventSource/Server-Sent events: lesson learned

Recently I have been looking into Server-sent events, also known as SSE or eventsource.

The idea of server-sent events is to push notification to the browser, in a way it could be seen as a read-only web-socket (from the browser's view).

Implementing SSE is fairly easy code-wise, this article from html5rocks pretty much covers all the basics, but the principle is:

  • Add a little javascript to make your page connect to a specific URL on your server
  • Add a little more javascript to your page to react upon messages sent by the server



Server-side, things are also fairly easy but also need a little consideration:

  • You need to create basically a streaming server, broadcasting messages as they occurs or whenever you want.
  • The format is fairly simple: data: <your data> \n\n
  • You cannot run this server behind apache. The reason is simple, the browser keeps the connection open which means apache will keep the worker process running. So after opening a few pages, apache will reach its maximum number of worker processes running, thus ending up in a situation where it is waiting forever for an available worker process (ie: your apache server is not responding anymore).

So after running into the third point listed above, I moved the SSE server out of my flask application and into its own application, based on trollius (which is a backport of asyncio to python2), but any other async libraries would do (such as twisted or gevent).

After splitting the code out and testing it some more, I found that there is a limitation on the number of permanent connection a browser can make to the same domain. I found a couple of pages mentioning this issue, but the most useful resource for me was this old blog post from 2008: Roundup on Parallel Connections, which also provides the solution on how to go around this limitation: the limit is per domain, so if you set-up a bunch of CNAME sub-domain redirecting to the main domain, it will work for as many connection as you like :-) (note: this is also what github and facebook are using to implement web-socket support on as many tabs as you want).

The final step in this work is to not forget to set the HTTP Cross-Origin access control (CORS) policy in the response sent by your SSE server to control cross-site HTTP requests (which are known security risks).



So in the end, I went for the following architecture:

SSE_layout3.png

Two users are viewing the same page. One of them edits it (ie: sends a POST requests to the flask application), the web-application (here flask) processes the request as usual (changes something, updates the database...) and also queue a message in Redis information about the changes (and depending on what you want to do, specifying what has changed).

The SSE server is listening to redis, picks up the message and sends it to the browser of the two users. The javascript in the page displayed picks up the message, processes it and updates the page with the change.

This way, the first user updated the page and the second user had the changes displayed automatically and without having to reload the page.



Note: asyncio has a redis connector via asyncio-redis and trollius via trollius-redis.

Wednesday, June 17 2015

Contribute to pkgdb2

How to get started with contributing to pkgdb2.

Continue reading...

Thursday, May 7 2015

Check packages in anitya and pkgdb2 for monitoring

A little while ago I presented a script allowing to search for the packages of a specified user and see which are missing from either anitya or are not being monitored in pkgdb2.

This script however, only check someone's packages and someone time we want to check a number of packages at once, eventually, all the packages matching a given template.

This new script does just that:

 $ python pkgs_not_in_anitya_2.py 'drupal-*'
   drupal-service_links                 Monitor=False   Anitya=False
   drupal-calendar                      Monitor=False   Anitya=False
   drupal-cck                           Monitor=False   Anitya=False
   drupal-date                          Monitor=False   Anitya=False
   drupal-workspace                     Monitor=False   Anitya=False
   drupal-views                         Monitor=False   Anitya=False

If you are interested, feel free to use the script

Wednesday, May 6 2015

Flock 2015: Your vote has been recorded. Thank you!

The election to select the talks for flock 2015 has started yesterday.

Anyone having signed the FPCA and being in one more group can participate to this election and help selecting the most interesting talks to be held at flock 2015 in Rochester (NY). Some of the talks submitted there look really interesting, I am looking forward seeing the agenda and I hope the ones I want to see will not conflict too much :-)

This year the election is using the simplified range voting approach. The principle is the same as for the classical range voting, but instead of having the possibility to score each candidate between 0 and X (X being the number of candidates, which is 132 for this election), you have the possibility to score each candidate between 0 and 3.

You can of course make your own scale but I went for something along the lines of:

  • 0: not really interested by this talk
  • 1: can be interesting, not sure
  • 2: looks like an interesting talk
  • 3: I really want to see this talk



And you, did you vote?

Monday, April 20 2015

PyCon 2015 - Montreal

This year, for the first time, I have been lucky enough that I could attend PyCon, the Python Conference.

This conference changes location every two years and this year was the second edition at the Palais des Congrès in Montréal, Canada.

Before I venture further into the conference itself, I would like to thank the organizers. The location was great! The organization flawless! And, as an attendee, everything went really smooth.

The conference itself is divided upon three sections

  • The tutorials and the language summit (2 days)
  • The conference per say (3 days)
  • The sprints (4 days)

I did not attend the tutorials but I was invited to the language summit by Kushal Das (PSF board member and CPyton contributor). I was a unique occasion for me to meet and discover how things are discussed and decided within the python community. I must say it made me want to participate more in this community, join the mailing lists and, who knows, maybe try to tackle some easyfix bugs :)

During the summit we had a number of presentation about alternative python compilers like jython. We also had a short presentation by Guido about changes coming in python 3.5 to support declaring types in the function definition. Another interesting discussion was around the requests library and if it could ever make it into the standard library. While I think that specific question wasn't really answered during the summit, it triggered some interesting discussion around endorsing some external libraries within the documentation of the standard library (ie: advising users to use requests on the urllib documentation pages). Another really interesting topic that has been presented was the state of python on mobile platform (Windows Mobile, iOS and Android). While there are still some more work that needs to happen things seems to be progressing on that front and I'm quite looking forward the day we'll be able to easily ship python application in the different store.

The second day of the tutorials was more relax for me. I took this opportunity to wander around Montreal a little and joined the crew of volunteers at the end of the morning to help preparing the swag bags for every attendee of the conference.
We first took out all the goodies shipped to the conference by the different sponsors and align them on two long tables. Then in the middle of the afternoon we started the 'bag stuffing' process :) This is a complicated process in which experts are carrying bags along the two long tables and another set of experts are translated items from the table into the bags.
Placing myself at the very beginning of the chain, I have probably been in contact with 2500+ bags of the 3000+ bags prepared (I would set the bags and be helped by one or two person that would either give away the bags or help me setting them up depending on the stash of prepared bags :)).
These were some interesting, fun, relaxing and sportive two and half hours! If you have not had the opportunity to stuff bags this year and are going to pycon next year, I highly recommend you to join this crew. It is a lot of fun!

The following three days have been the conference itself. To summarize, here is an overview of the talks I went to over the three days: Friday

  • Opening: Julia Evans
  • Keynote: Catherine Bracy

on the Coding For America project and in a broader sense what I would call, civic coding. (ie: how developper can help the community at large by making publicly accessible information and tools). This was a really great keynote, her talk was inspiring and motivating as well as calling for further reflection upon the roles of FOSS developper in our society within our field of expertise (developing) but outside our traditional scope (web, desktop, OS, company).

  • Machine learning 101: Kyle Kastner

This was also a very interesting talk going over the different machine learning algorithm, libraries and use-cases. That helped getting an overview of the field

  • Introduction to HTTPS: A comedy of errors: Ashwini Oruganti & Christopher Amstrong

This was presenting what are the current issue when dealing with https in general, within python or not. I can't say I learned new things in there but it is always good to get refreshed on this topic

  • Insite the Hat: Python @ Walt-Disney Animation Studios: Paul Hilderbrandt

This was a really interesting presentation about the use of IT in general (and python in particular) at Walt-Disney Animation Studios and of course it was full of pretty pictures from Big Hero 6 as well as some other pretty pictures from a couple of other movies. Paul also presented the overview of how animation movies are made and how Disney developed their own tools to facilitate this process insisting on the idea that the tools have to adapt to the artist rather than the other way around.

  • How to interpret your own genome using (mostly) python: Titus Brown

This talk presented tools and workflow that can be used to analyze and compare genomes, taking a population that had a particular history as example and going down into the genome to figure out what (at the gene level) makes this population so specific. It also gave an overview of the possibility for high-throughput genome sequencing and the application that can derive from it as well as touching the surface of the ethical concerns that raises from these technologies.

  • How to build a brain with Python: Tevor Bekolay

While still being bioinformatics this was a very different topic than the previous talk I attended. This presentation was really about the inner (ie: chemical and physical) modeling of neurons of a brain. The presentation started by introducing a couple of application used to model a single neuron and then introduce their own application used to model several neurons at once. Quite impressive and interesting presentation although knowing more about the biochemical and biophysical properties of the brain would have probably lead to a better comprehension of the work presented :)

Saturday

  • Introducing python wats: Amy Hanlon

While I must say I knew most the example she presented of curious behavior of python, I must say that I did not know completely the reason of these behaviors. The presentation was really nice in that it gave some clues and as well as some tools to help figuring out what is actually happening in the code and why these, sometime surprising, behaviors.

  • Learning from other's mistakes: Data-driven analysis of python code: Andreas Dewes

This was an interesting presentation describing the approach develop by this company to do static code analysis but considering the code not as text but as a graph. This approach allows to find out bugs in the code due to, for example, typos in property names. It seems that the service is freely available but unfortunately, if I understood correctly, the tool is not FOSS.

  • Technical Debt - the code monster in everyone's closet: Nina Zakharenko

The interesting bit about this presentation is that anyone that worked on a reasonable size project could relate to what was presented. There are many times where I thought that I have been in the situation described and some time when I thought I wasn't doing too bad (but here I guess it depends on the projects). There were some good elements to help figuring out the size of the debt as well as some good ideas on how to organize the work to reduce this debt.

  • Achieving continuous delivery: An automation story: James Cammarata

This presentation was about Ansible and how different companies are using it to automate their deployments. Several examples of companies were given, some even integrating Ansible with an IRC bot allowing everyone on the IRC channel to see what the other admins are doing.

  • Build and test wheel packages on Linux, OSX and Windows: Olivier Grisel

Wheel are a format that can be used to compile python packages into binaries that can then be installed on multiple platforms. There are clearly some advantages in this but I am not quite convince especially with regards to architecture specific code and the different architectures that we have today (x86, arch, arch64, ppc...) But anyway, since Fedora does not allow shipping binary files directly wheel isn't quite an option for us. On the other hand it might be one for applications such as liveusb-creator or pyrasite that aim at being cross-platform.

  • Graph database patterns in python: Elizabeth Ramirez

The presenter of this talk works at the New-York Times journal and was presented the approach the use internally (as well as the tools and library) to store semantic concepts, link them and navigate the graph they make. After the presentation I ended up having a very interesting talk about the difference between full-graph database and rdf databases and what the former allows that the later does not. While I am still a little unclear about this difference, it was a really interesting conversation and something I would like to look further into if I was still working with/on semantic web technologies.

Sunday

  • Keynote: Van Lindberg

This was a presentation from the head of the PSF board about the state of the python community and python in general, how it went from being a trendy language when it was created into something stable and sure these days, but also how other languages are growing, potentially threatening python by being the new trendy languages. Community wise, I have written one quote from this talk that I really like:

  A community where people interact only when they are paid to do
  so is not a community, it's a bunch of mercenary
  • keynote: Jacob Kaplan-Moss

This was a great talk about the perception that we have as developers of themselves. For example, did you realize that there are two kinds of developers: the great ones and the terrible ones while if the quality of a developers could be quantified we know that just like everything else it would follow a normal distribution, ie: most people would be average developers and only a few would be great and a few would be terrible. If you have seen it I would like to say:

 Hello, I'm pingou, I'm a mediocre programmer

If you haven't seen it, I invite you to watch it as it was an inspiring talk, really.

  • Interactive data for the web - Bokeh for web developers: Sarah Bird

Bokeh is a library that can be used to create interactive graph that can be included in web pages. The examples shown during the presentation were really impressive and while it probably needs some understanding of the different ideas, concepts and of the library itself, it is definitively something I will look into the next time I have to do some data visualization.

  • WebSockets from the wire up: Christine Spang

While I have heard about web-socket I have not had the opportunity to play with them more than this. In this talk the history and principles of web-socket was described, giving a nice idea of what they can be used for. I must say I know kinda want to play more with them, build more reactive UI using web-sockets. However, for the projects I work on these days I feel it would be a little bit overkill. Maybe for next one ;-)

  • Type hints: Guido Van Rossum

This was a very similar presentation to the one Guido gave during the language summit, presenting the work coming in python 3.5 to support type documentation in function definition. Here, as well as during the language summit, I got quite enthusiast about this idea but the syntax of putting the type in the function definition is really not appealing to me. It makes the function definition both harder to read and, in some case, much longer. To be honest I would love to see the same syntax be supported in docstring which is where I believe it belongs (plus, as a bonus, it kind of encourage developers to document their code, if you start writing docstring for the type, maybe you can add documentation about the arguments themselves and the function, and so on).

  • Keynote: Gary Bernhardt

This keynote was probably the most technical keynote we had (except for Guido's presentation just before). It presented a comparison between strong type languages and dynamic type languages.

This is it for the talks I attended. There are more talks I would have liked to see but either I was doing something else or there was another talk at the same time. Luckily all the talks have been recorded and are available on youtube.

Among the talks I would like to see are:

  • Building secure systems - lvh
  • What can programmers learn from pilots? - Andrew Godwin
  • "Words, words, words": reading Shakespeare with Python - Adam Palay
  • Is your REST API RESTful - Miguel Grinberg
  • l18n: World domination the Easy Way - Sarina Canelake
  • Good test, Bad test - Dan Crosta
  • How our engineering environments are killing diversity (and how we can fix it). - Kate Heddleston
  • Open Source for Newcomers and the People who want to welcome them - Shauna Gordon-McKeon
  • Cutting off the internet: Testing applications that uses requests - Ian Cordasco
  • Rethinking packaging, development and deployment - Domen Kozar
  • Describing descriptors - Laura Rupprecht
  • Avoiding burnout, and other essentials of Open Source self care - Katheleen Danielson
  • Python performance profiling: the Guts and the Glory - A. Jesse Jiryu Davis

As you can see I'm in to spend few hours watching youtube videos :)

The third part of the conference was the sprints.

The idea of the sprints is to take advantage of the fact that many developers come to the conference to keep them a little longer and offer them projects to work on.
During these four days, you can see people hacking on Django, MailMan, Jython, CPython itself, sage, pypy and many more projects. I took this opportunity to spend more time with the people from my team not that we don't work together most of the time but it is nice to be working together in the same room. As for the project, most of the time has been spent on making pagure closer to something we would want to deploy/use. I must say that at the end of this week, since are looking good. Pagure now has support for webhooks, pull-requests can be assigned, they have a score and the project can require a certain score for a pull-request to be merged. Basically, for what I want pagure needs: a) more documentation, b) more unit-tests and c) more tests and d) support to upload tarball/release (although this might arrive only in 0.2). So once documentation and unit-tests are there, I will tag a 0.1 release and move pagure to production (I'll announce it here so keep in touch! ;-))

As final words, I started this (long, sorry) blog post with saying how lucky I am to actually having been able to attend this conference and I would like to thanks Red Hat in general and more precisely the OSAS team that funded my flights and pass for the conference.

Tuesday, April 14 2015

FOSS Emoji

Just wanted to make a quick note here.

Today looking for emoji for pagure I ran into http://emojione.com/. This project provides Free and Open Source emoji icons that can thus be re-used on other projects.

Just heads up to those looking for a FOSS emoji database/project and big thanks to the developers and artists behind this awesome project!

Friday, April 3 2015

OpenSearch integration in pkgdb

One of the earliest feature request of pkgdb2 (that was present in pkgdb1) is the browser search integration.

This integration is based on the OpenSearch specifications and basically allows to use pkgdb as one of the search engine of your web browser just like you can use google, duckduckgo or wikipedia.

I recently found out this feature is not so well known, so I thought I would present it and explain how to set it up (screenshot are on Firefox).

1/ Go to https://admin.fedoraproject.org/pkgdb and click on the list of search engines at the top right.

2/ Select the entry Add "Fedora PkgDB2: Packages"

That's it you are done for the most important step :)

pkgdb_search_3.1.png

Now something which I do and find most useful is:

3/ Go to Manage Search Engines...

There, with the search engine pkgdb packages associate the keyword pkgdb

pkgdb_search_5.png

Now, you can use your url bar as usual but when you enter pkgdb <something> it will search this <something> in pkgdb directly. So for example, if you want to search for guake in pkgdb, you would type in your url bar pkgdb guake.

pkgdb_search_6.png

The bonus point is that since there is only one package with this name, you will be immediately redirected to its page.

This way, when you want to quickly find information about a package in pkgdb, you can get it from your browser in one simple step (eventually two if several package match the keyword you entered).

Final bonus point? To access pkgdb directly, enter in the url bar: "pkgdb " (with a space at the end), without a keyword, Firefox will bring you directly to the front page of the application.

Wednesday, March 25 2015

Progit is dead, long live pagure

You may have heard of a little pet project I have been working on recently, I called it progit but there already a more well-known project named progit (the pro git book).

So, after long deliberations, we decided to rename the project: pagure.

What is Pagure?

Pagure is a small git-centered forge project. You can host your code, your documentation, your tickets and have people contribute to the project by forking it and opening pull-requests.

All the information about the project is hosted in different git repositories, the code of course, but also the documentation as well as the metadata (discussion) of tickets and pull-requests. The idea being that one could host a project in multiples instances of pagure and keep them in sync.

What about the name?

Pagure is the generic (French) name for animals of the Paguroidea family which includes the well known Pagurus bernhardus. This little crab moves from shell to shell as it grows up. I found it was a nice analogy with this forge where project can move from place to place.

Where can I see it?

Pagure is still under development and pretty much changes every day. However, you can already see it, test it and poke at it via the dev instance we have running.

As you will see, pagure itself is being developed there, so feel free to open a ticket if pagure does not do something you would like (or does something you do not like).

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