Erlang

MongooseIM 3.1 - Inbox got better, testing got easier

by Piotr Nosek

This summer the MongooseIM team have not had a second to be lazy - the development of MongooseIM 3.1 release took over what was supposed to be our downtime, when all major activities driven throughout the year slow down. We’re happy to say that in this time of leisure, the new release is packed with important features, improvements and excitement. Take a look at the version highlights and be part of this major step in creating a world-class communication server.

This time, a large part of the changes are focused on development efficiency, but rest assured, we’ve added new items you are going to appreciate.

In the “Test Runner” section, you get to learn all about a little tool we provided so that you can easily set the development environment up and run tests locally without Travis CI.

Our Inbox extension has got three big updates that push the boundaries of what’s currently offered in XMPP world. As a rule, we want to lead by example; less talk and more action. That is why working in cooperation with Forward, we decided to put forward an implementation of a popular use case as a unique feature in this software sector.

This release is also an important lesson for us. A lesson about edge cases and concurrency in integration testing. You don’t necessarily have to be an Erlang developer to benefit from the third section, but reading it allows you to learn with us.

The “Honorable Mentions” section may seem minor, but for some projects the items listed there can indeed make a difference! It’s a candy mix of different changes, so read carefully not to miss your favourite flavours!

Obviously, a single blog post is too small a space to tell a profound story about every new item in the changelog, so we encourage you to check it out. You can find a link at the bottom of this blog post.

Test Runner

The Travis CI is our main verification tool for the Pull Requests we create and merge. Whilst being convenient and critical for our process, it is not very handy for day-to-day development. It is very common to frequently execute limited subset of tests to ensure that a new piece of code we wrote works perfectly. However, waiting for Travis results every time would extend implementation time excessively as it executes multiple presets, while being a shared resource at the same time.

The test runner is a script that helps to set the development environment up, and run tests on a developer machine locally. The test runner shares a lot of code with our Travis CI build scripts, which ensures that test results are consistent between local and CI runs.

The test runner allows to choose which tests to run. It can be useful, when one of the tests is failing and we want to rerun it.

Since MongooseIM supports different database backends, the test runner is able to set a selected database up for you and configure MongooseIM. Simply put, it prepares the local environment before executing actual test suites.

The test runner supports a lot of options to customise your build and test execution scenario. It also supports shell autocompletion for option names and values.

We’ve prepared a recording for you that presents a basic usage of the script.

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Please note that Asciinema allows you to pause and copy any text fragment you like, so it would be very easy for you to repeat the same steps.

New Inbox Features

Originally sponsored by and created for Forward, Inbox has been available as an open source extension for the last two months already. In MongooseIM 3.1, it returns with a bundle of fresh goodies. The first feature is MSSQL support.

Despite being less frequently used with MongooseIM compared to MySQL or PostgreSQL, it’s still an important piece of the architecture for many projects, especially those running in Azure cloud. We don’t want you to feel excluded, dear Microsoft users!

The second one is the support for classic MUC group chats. MUC Light was never intended as a complete replacement for original XEP-0045 solution. It means that numerous projects exists where mod_muc is still a better match than its younger sibling, and they may now benefit from inbox features as well!

Last but not least is the timestamp support. First of all, they are stored in DB and returned in Inbox query results. For those using mod_inbox from MIM 3.0: you’ll need to update your schemas but don’t worry - it isn’t very complicated. What’s more, a client may now request conversations from a certain time period and sort them by timestamp, both ascending and descending.

This is not our final word on this matter. You may expect further improvements to this extension in upcoming MongooseIM versions!

We’ve prepared a demo of the Inbox feature. It shows both the backed and the frontend side of it. The application used in the demo has been designed by Forward.

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Lessons learnt regarding CI

OK, these are short and sweet but nevertheless important:

  1. Avoid RPC in integration tests. They tend to time out in slow CI environments (such as Travis).
  2. When test users exchange messages, always wait until they are received to ensure proper synchronisation.
  3. On a slow machine, MSSQL SELECT query may return more than one row (even when retrieving by the exact primary key value) as a consequence of the transaction deadlock.
  4. When you can’t use any other means of server state synchronisation, don’t use hardcoded sleep periods; replace them with an incremental backoff and verification in a loop. Sometimes you can’t predict whether a server state is updated properly in 500ms, 1000ms or 3000ms. Adding 5s waits everywhere may cause test suites to run veeery long.
  5. Be careful about leaking presences between cases. This applies to XMPP testing. Best practice is to generate fresh user accounts for every scenario.
  6. Some databases don’t support transactions so the new data may not be instantly available. For example, in the case of Riak (its Search function in particular) a delay between data insert and query is required.
  7. Sometimes creating a schema in a DB may fail for the first time due to timing issues, so implement a retry loop in a DB provisioning scripts. This also applies to Riak.
  8. Did I mention creating new user accounts for every test case? It actually applies not only to XMPP. With this practice, you won’t have to worry about possible leftovers of a user’s state.

Honorable mentions

ElasticSearch backend for Message Archive

Almost every MongooseIM module supports more than one type of backend. Usually it’s Mnesia, RDBMS and sometimes Riak. Message Archive Management is a noteworthy exception, as we’ve implemented RDBMS, Riak and Cassandra support for this module. Or “modules” actually, as it consists of over 30 Erlang files already.

It is a very special feature as it processes a vast amount of data and sometimes executes expensive queries. In order to ensure performance and match a project’s architecture, wide range of supported DB backends is essential.

It is our pleasure to announce that yet another backend has joined the family: ElasticSearch.

OTP 21 support

OTP 21.0 has been released ~1 month ago and we’ve added support for this version less than a week after! This is great news for all projects sticking to the most recent Erlang technology as pioneers in BEAM world. The new platform version brought not only improvements in regards to performance but also some incompatibilities that we’ve resolved, so MongooseIM still remains at a technological peak.

As a tradeoff, we’ve dropped official support for OTP 18.x. It should still be possible to compile 3.1 with this version with some minor code modifications, but we’re definitely moving forward. It has allowed us to get rid of non-typed maps specifications as an example. As a reminder, bear in mind, that MongooseIM always supports two most recent, stable OTP branches (currently these are 20.x and 19.x and one being under an active development, 21.x).

Jingle/SIP tutorial

SIP is a common choice for VoIP applications but certain XMPP features may be a very good match for such software. MongooseIM is able to liaise between these two worlds and now it’s easier than ever with significantly extended documentation (compared to the level in 3.0) and a tutorial on mod_jingle_sip usage.

Worker pool unification

Every developer writes a custom worker pool at some point of their career. Everyone. Certain MongooseIM components (the ones that use connection pools) were created with different preferred library in mind. As a result, we’ve ended up with many kinds of worker pools: cuesport, worker_pool and poolboy. It wasn’t only a matter of maintenance difficulty, but performance as well. As an example, cuesport supports only a simple round-robin job assignment algorithm, which is not optimal in every case. It also lacks inspection of any kind.

Given our experience gathered over the years, we’ve selected worker_pool as our primary library. It is very flexible and exposes a dedicated stats API. It was originally created by Inaka and it is actively maintained by its former developers at this present time.

For now, the changes are purely internal. Some projects may observe better performance but the primary goal was to prepare for a second round of unification. Stay tuned for more details in near future.

Changelog

Please feel free to read the detailed changelog. Here, you can find a full list of source code changes and useful links.

Contributors Special thanks to our contributors: @SamuelNichols @Beisenbek @GalaxyGorilla!

Test our work on MongooseIM 3.1 and share your feedback

Help us improve the MongooseIM platform:

  1. Star our repo: esl/MongooseIM
  2. Report issues: esl/MongooseIM/issues
  3. Share your thoughts via Twitter: @MongooseIM
  4. Download Docker image with new release
  5. Sign up to our dedicated mailing list to stay up to date about MongooseIM, messaging innovations and industry news.
  6. Check out our MongooseIM product page for more information on the MongooseIM platform.
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