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Call for Papers application created for Devoxx France, used by many conferences


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Call for Papers application

The CFP is a Call for Papers application for Conferences.

The application allows a speaker to register with Github/Google+ or LinkedIn, then post one or more proposals for a Conference.

A program committee can then vote, ask questions to speaker and finally, build an Agenda for a conference. The CFP offers also a REST API with the list of selected talks, speakers and the schedules.

In 2015, the Devoxx France's CFP received 681 proposals for 220 slots. The 16 members of the technical committee for Devoxx FR did more than 6700 reviews in 2 months.


Original author: Nicolas Martignole @nmartignole


The CFP application is licensed under the MIT License. See License.txt or

Copyright (c) 2013 Association du Paris Java User Group & Nicolas Martignole.


The CFP was originally created in 2013 for the Devoxx France 2014 edition. Devoxx France is one of the biggest conference for Developers in France with 2500 attendees in 2015. The conference had top sponsors like Google, Oracle, IBM and Microsoft. The conference is organized by Nicolas Martignole, Antonio Goncalves and Zouheir Cadi.

The CFP is implemented with Scala and Play Framework v2.2.3. Redis 5.x is used for persistence. Elastic Search is integrated as a search engine and to calculate stats with Facets.

Which Conferences are using it?

Send a message to @nmartignole if you plan to use the CFP.

How to set-up a developer environment ?

Gitpod Intellij-based environment

Gitpod is a cloud-based IDE which provides 50h / month on his free tier (they can also provide unlimited usage for OSS projects)

Steps for a proper setup :

  • Create a Gitpod account (if you don't have any) and allow Gitpod to access your Github repository
  • Follow Gitpod's Intellij IDEA getting started steps to be able to use Intellij as your Gitpod preferred IDE
  • Install following plugins on your local Intellij (unfortunately, those plugins are not compatible with a cloud-based IDE at the moment) :
  • Open gitpod url with the target branch in it, something like :
    You can also install a browser extension (Firefox | Chrome-based) which will help generate the proper gitpod url based on your selected github branch.
  • You will need to wait a little bit that Gitpod provisions the VM
  • Once your cloud-based Intellij is opened, a browser window should be opened automatically with the CFP webapp in it (the browser window may take some time, maybe 3-4 minutes, on first opening, as every Twirl templates are going to be compiled)
  • Create a speaker user on the CFP and look into the console to see the confirmation email ("please validate your email...") with a link and click it to confirm user creation. Complete creation form by entering a short bio and validate.
  • Once your profile has been confirmed, edit your profile (/cfp/profile) and look for your UUID at the bottom of the webpage.
  • Open magic URL /admin/bootstrapAdminUser?uuid=<put here the uuid> in order to promote your user as an admin user, so that you're able to create new users or promote them as admins.
    Important note: this magic URL will work only if no admin already exists on your CFP instance

If, for whatever reason, you want to look at Redis which is used as our DB, you should have a dedicated terminal window connected to current Redis instance.
In this console, you can for example execute key * query to gather all existing Redis entries.
For more information about Redis, don't hesitate to look at its documentation here

Gitpod Debug

If you want to debug Scala code, then there is a dedicated Shared Run Configuration for this that can be run in debug mode

Switch on the Play run terminal tab and stop it by clicking on Ctrl+C multiple times. Then click on Debug 'Run CFP' on the top menu bar, which is going to start the app in debug mode.

Uploading Redis dump to Gitpod instance

You can upload big files to Gitpod by running a "cloud commander" on your gitpod instance :

  • From anywhere in your workspace, run : npx -y cloudcmd This should run a webserver on port 8000 (by default)
  • Once done, open another terminal and execute following command in order to open (temporarily) your cloud commander : gp url 8000
  • In the cloud commander UI, you will be able to upload any file on your gitpod filesystem, so you will be able to upload your rdb file in your workspace (please, don't upload it in redis-data/ yet)
  • Disable appendonly on your redis instance : docker exec cfp-devoxx_redis redis-cli CONFIG SET appendonly no
  • Stop your redis image (docker stop cfp-devoxx_redis)
  • Move your uploaded rdb file to redis-data/dump.rdb file
  • Start again redis : docker start cfp-devoxx_redis
  • Re-enable appendonly : docker exec cfp-devoxx_redis redis-cli CONFIG SET appendonly yes
  • You should be able to see that your dump is loaded by running : docker exec cfp-devoxx_redis redis-cli keys '*'

Local development environment

You can look at .gitpod/base.Dockerfile to replicate what to install (SBT 0.13.18, Scala 2.11.12 etc.)

Make sure that you have installed a JDK such as Open JDK 11

➜  cfp-devoxx git:(dev) java --version
openjdk 11.0.6 2020-01-14
OpenJDK Runtime Environment GraalVM CE 19.3.1 (build 11.0.6+9-jvmci-19.3-b07)
OpenJDK 64-Bit Server VM GraalVM CE 19.3.1 (build 11.0.6+9-jvmci-19.3-b07, mixed mode, sharing)

Additionally, to run Redis (and Elasticsearch) you can run docker-compose up -d (you can learn Redis with its documentation)

Optional but recommended for better user experience:

Production configuration

  • Generate a string for the security of the application application.secret = "a_unique_secret_long_enough"
  • As the application uses play.api.libs.Crypto#encryptAES, this secret MUST be at least 16 chars long.
  • Configure the SMTP server using the parameters Mailjet OR use the smtp.mock mode in DEV
  • Configure the Github part
  • Set the Google party for authentication OAuth2.0
  • Configure also LinkedIn
  • configure the Redis server. Make sure to set a very long password for your Redis server
  • configure the address of a server ElasticSearch

Where do I start?

First things first, you need to set-up your own conference. To do so, Frederic Camblor implemented a generic class that contains most (but not all) importants details. Check ConferenceDescriptor.scala. This file defines the configuration of your own conference. The Schedule/Slots is not mandatory when you start to configure your application. However if you plan to use the REST API then you should also configure this part. Check for the TODO's in the file.

You can then also translate and check messages/ from the conf file

How can I create a new user?

To create an admin:

  • Start the CFP with a local Redis server
  • Create a new User (http://localhost:9000/home) with the Registration system
  • If you configured smtp.mock="yes" in application.conf, check the console. You should see the "please validate your email" message
  • Loads and validate your user
  • Once authenticated, retrieve your UUID from the "Edit my Profile" page (/cfp/profile)
  • Load the bootstrap URL http://localhost:9000/admin/bootstrapAdminUser?uuid=[your_uuid]. Please note that if there is already an admin, this won't work.

You can also add an existing user to the Admin group directly from Redis console :

In term of Git, how can I push a new feature?

The main development branch is dev. It' an out-of-the-box ready to use conference. This is also where I try to collect all features from all contributors.

I created a branch dev-france for current development regarding Devoxx France. I did the same for BE. I work with one feature per branch, then do local merge.

When you want to update your local branch (for instance, dev-poland) you should :

- do a checkout of dev
- do a git pull --rebase on dev
- switch to dev-poland
- do a git pull --rebase from dev to dev-poland so that you keep your local updates

How can I save my agenda and host the program as static content to a Wordpress ?

Use WGET and download all pages from your Publisher controller. This will save speakers, talks, schedule, etc.

wget --no-clobber --convert-links -r -p -E -e robots=off

Can you help me with Redis ?

On Mac, install redis 7.x using brew :

brew install redis@7

The CFP has been tested with Redis 7.04 Always check that your version is up-to-date in term of security

Create a custom redis configuration file. Be sure to set a very strong password. Redis is written in C and is mono-core. On my super Intel i7 it runs on one Core. Thus it's ok to have multiple Redis on differents ports.

How to run the redis server with custom config file ?

$ redis-server [xxx.conf-file]

Note: ensure all paths in the .conf file exists otherwise, use touch to create those files / paths

How to run the redis client ?

Once the redis-server is up and running, do the following:

$ redis-cli -p 6379

Some commands to remember:

> SYNC - helps sync remote server with local server (cluster)
> SMEMBERS Webuser:admin
> SADD Webuser:admin [sha1]

Once running on a local empty Redis, you will want to have a local user with admin privileges in the application.

  • Create a user and activate it

  • Play log will give you the activation link if running on smtp.mock=”yes”

  • Connect to the Redis instance

  • Find the UUID of the user you want to be admin

  • The command keys Webuser:UUID* will list all known user UUIDs

  • Find which one is your soon to be admin by running get Webuser:UUID: and the output gives you the email.

  • Add the UUID to admin and cfp groups using redis-cli (the redis CLI).

    SADD Webuser:admin SADD Webuser:cfp

If you want to promote an existing user to admin on your PROD server, you can also use redis-cli to connect to the remote server Let's say you want to add John with ID=UUID_123456 to the remote PROD that is running on port 6393. The Master password on this remote server is "my_super_password_for_prod".

nicolas@macbook :~/Dev/DevoxxFR/2014/RedisBackup> redis-cli -h -p 6393> info
NOAUTH Authentication required.> AUTH my_super_password_for_prod
OK> SADD Webuser:admin UUID_123456> SADD Webuser:cfp UUID_123456
  • Restart the application to clear its caches (or use /admin/clearCaches if you are already an admin and connected)

Redis is an in-memory server... How can I be sure that I won't loose my data ?

First, read the Redis documentation. I use AOF and BGSAVE on my production servers. I also use Linux Dropbox client so that I can save some dump automatically. I have also configured my personal computer to be a slave of all my Redis servers. This is very practical, you get a live copy of Redis on your laptop.

See redis-sample-dev.conf and redis-sample-prod.conf for 2 valid configuration files for Redis.

Just to give you an idea and some stats for our Devoxx France 2015 Redis database :

- Number of Speakers : 946
- Number of Proposals : 681 
- Number of Reviews : 6704
- Redis DB Size : 8388
- DUMP file size : 65M
- AOF file size : 73M
- Number of lines in the AOF file : 2,344,818
- Memory used by Redis : 142 Mo

Where do you host your CFP for Devoxx France?

The Devoxx France CFP is hosted on Clever-Cloud. Clever Cloud is a Platform as a Service. Git push and voilà, your code is deployed. Redis and ElasticSearch are on a dedicated server.

Why do you use Play 2.2.x and not the latest version?

I recommend Play 2.2.6. I have a strong experience with Play since 2011 and Play 1.x. I did more than 20 presentations of Play! Framework since 2010.

I plan to evaluate the need to migrate to Play Framework 2.4. But I'm not a super-fan with this version and with what the core developers decided to do since early 2015.


Pull requests are welcome but be aware that the CFP is really focus on Devoxx conferences.

The following is a list of absolute requirements for PRs (not following them would result in immediate rejection):

  • You MUST use space for indentation instead of tabs
  • The coding style MUST be followed exactly (default IDEA IntelliJ 14 settings)
  • Each commit MUST be a single change (e.g. adding a function or fixing a bug, but not both at once)
  • Each commit MAY respect the Commit log convention (see below)
  • The pull request MUST contain as few commits as needed
  • The pull request MUST NOT contain fixup or revert commits (flatten them beforehand using GitUp!)
  • The pull request MUST be rebased on latest dev when sent

Git Commit Guidelines (from AngularJS source code)

We have very precise rules over how our git commit messages can be formatted. This leads to more readable messages that are easy to follow when looking through the project history.

Commit Message Format

Each commit message consists of a header, a body and a footer. The header has a special format that includes a type, a scope and a subject:

<type>(<scope>): <subject>

The header is mandatory and the scope of the header is optional.

Any line of the commit message cannot be longer 100 characters! This allows the message to be easier to read on GitHub as well as in various git tools.


If the commit reverts a previous commit, it should begin with revert: , followed by the header of the reverted commit. In the body it should say: This reverts commit <hash>., where the hash is the SHA of the commit being reverted.


Must be one of the following:

  • feat: A new feature
  • fix: A bug fix
  • docs: Documentation only changes
  • style: Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc)
  • refactor: A code change that neither fixes a bug nor adds a feature
  • perf: A code change that improves performance
  • test: Adding missing tests
  • chore: Changes to the build process or auxiliary tools and libraries such as documentation generation


The scope could be anything specifying place of the commit change, usually related to a Play Controller. For example admin, api, publisher, etc.


The subject contains succinct description of the change:

  • use the imperative, present tense: "change" not "changed" nor "changes"
  • don't capitalize first letter
  • no dot (.) at the end


Just as in the subject, use the imperative, present tense: "change" not "changed" nor "changes". The body should include the motivation for the change and contrast this with previous behavior.


The footer should contain any information about Breaking Changes and is also the place to reference GitHub issues that this commit Closes.

Breaking Changes should start with the word BREAKING CHANGE: with a space or two newlines. The rest of the commit message is then used for this.

A detailed explanation can be found in the AngularJS Git commit documentation.

CSS and Bootstrap theme

We migrated to Bootstrap 4.3 with the Bootswatch Theme Flatly

Please report any issues or CSS errors on Github issues.

Call for Paper application for Devoxx


Le CFP de Devoxx France est codé en Scala, avec le framework Play 2.2.x. Les données sont persistées sur Redis. J'ai écris cette application en prenant soin de rester simple, pragmatique et productif.

Caractéristiques et idées du nouveau CFP :

  • Authentification et inscription possible via OpenID (Google et Github)
  • Utilisation du format Markdown pour saisir sa proposition de sujet
  • Les photos des speakers sont tirées du site Gravatar
  • Importation du profil Google+ ou Github pour accélérer la création du profil
  • Pas de framework JS côté client sauf si cela devient une nécessité
  • Du code Scala simple et facile à lire

Installer un environnement de développement local

L'installation d'un environnement de dév est simple et s'effectue en quelques étapes :

  • installer Play 2.2.3
  • installer Redis
  • configurer son serveur Redis pour être "slave" de la prod
  • récupérer le code source du projet CFP Devoxx France de Bitbucket
  • lancer et commencer à contribuer

Installation de Play 2.2

Pré-requis : Java 11 fortement conseillé pour des raisons de performances.

➜  cfp-devoxx git:(dev) java --version
openjdk 11.0.6 2020-01-14
OpenJDK Runtime Environment GraalVM CE 19.3.1 (build 11.0.6+9-jvmci-19.3-b07)
OpenJDK 64-Bit Server VM GraalVM CE 19.3.1 (build 11.0.6+9-jvmci-19.3-b07, mixed mode, sharing)

Installation de Redis 5.0.3

Pré-requis : les utilitaires make, gcc correctement installés via XCode ou brew.

Configurer votre serveur Redis

Lorsque vous développez sur votre machine, nous allons utiliser un serveur Redis local afin de pouvoir y écrire nos données, sans perturber la production. Cependant, un des points forts de Redis, c'est qu'il est possible de synchroniser son serveur local avec un serveur Redis distant. Pour cela, nous allons déclarer que la prod, le serveur Redis hébergé à distance, est MASTER. Votre installation de Redis locale sera donc SLAVE de ce serveur. Redis synchronise rapidement, et vous aurez donc en permanence une copie de la prod sur votre machine locale.

Pour cela, il faut utiliser le fichier conf/redis-sample-dev.conf que j'ai placé dans le répertoire conf du projet Play2. Prenez ce fichier, copiez-le vers le répertoire par défaut de Redis, /usr/local/etc sur MacOS X.

Vous pouvez alors démarrer le serveur redis local avec la commande suivante :

redis-server /usr/local/etc/redis-devoxxfr.conf

Pour arrêter proprement le serveur, il suffit d'envoyer la commande SHUTDOWN au serveur :

redis-cli -p 6363 SHUTDOWN

Vous pouvez vous amuser avec votre serveur Redis en local avec l'utilitaire "redis-cli"

Celui-ci permet d'effectuer des commandes, je vous invite à suivre le petit tutorial pour mieux comprendre.

Reporter un bug

Le projet est hébergé sur Github

Installer sa propre version du CFP

Imaginons que vous êtes Breton et que vous souhaitiez installer ce CFP pour votre conférence :-)

Pour pouvoir faire tourner en production votre propre application du CFP, il est nécessaire de configurer différents éléments dans le fichier application.conf de Play 2.2.

Voici ce qu'il vous faut

Voici ce que vous devez configurer :

  • Renommez le fichier application-please-customize-me.conf en application.conf

  • Générez une chaîne de caractère pour la sécurité de l'application


  • Configurez le serveur SMTP en prenant les paramètres de Mailjet

  • Configurez la partie Github

  • Configurez la partie Google pour l'authentification OAuth2.0

  • Configurez enfin le serveur Redis. Prenez soin de configurer un mot de passe très long pour votre serveur Redis

  • Configurez enfin l'adresse d'un serveur ElasticSearch

Au moment de la mise à jour de cette documentation, la partie Trello n'est pas encore codée.



Le CFP de Devoxx France est hébergé sur la plateforme

Dernière mise à jour : novembre 2022