Changes/Erlang 19

Erlang 19

Summary

Update Erlang/OTP to version 19, and improve Erlang support in Fedora.

Owner

• Name: Peter Lemenkov, Fedora Erlang SIG, Randy Barlow, Jeremy Cline
• Email: lemenkov@gmail.com, erlang@lists.fedoraproject.org, rbarlow@fedoraproject.org, jcline@fedoraproject.org
• Release notes owner: Simon Clark (sclark)

Current status

• Targeted release: Fedora 25
• Last updated: 2016-06-30
• Tracking bug: <will be assigned by the Wrangler>

Detailed Description

Upgrade Erlang to version 19 which brings a lot of good stuff. Just a few highlights:

• A new state machine behavior - gen_statem.
• An experimental plugin to mnesia which allows using expernal storage solutions (leveldb, for example) - mnesia_ext.
• Cryptographic functions speedups.
• Even better dirty NIF schedulers.
• Experimental support for Unix Domain Sockets which opens a door for native Journald, systemd-notify, D-Bus implementations.

Aside from this, we plan to improve quality of Erlang and related packages. These are shortcomings we want to address:

• We should enable so-called dirty NIF scheduler which is still disabled currently.
• Every daemon written in Erlang has its own logging solution which doesn't use neither syslog nor Journald. We should start switching them to Journald.
• We should add ability to use D-Bus via erlang-dbus library.
• Further improve Erlang Packaging Guidelines.

Benefit to Fedora

Fedora users, both developers and end-users, will have visible benefits from using Fedora-provided packages. Namely:

• Even faster and better EC support in Erlang. Fast enough to start experimenting with cryptocurrencies using Erlang out of the box.
• More scalable and reliable applications with better performance.
• Improved logging, better unified with the rest of system.
• Packagers won't be afraid of packaging Erlang-related applications anymore. They will spend even less time on packaging and more time on actual development.

Scope

• Proposal owners:
  • Upgrade Erlang to the latest version (19.0.1).
  • We must rebuild every package which requires NIF or Driver version (listed below in the Dependencies section) against Erlang 19.x.y.
  • Every Erlang daemon's systemd unit must require epmd.socket.
  • Consider allowing EPMD implementation switching. Erlang is about choice!
  • We need to fill new review request for erlang-ejournald
    • We have to fill new review request for erlang-lager_journald_backend
  • We need to fill new review request for erlang-dbus
  • Add another default directory to look for Erlang *.beam files.
  • Upgrade outdated packages:
    • Riak
      • Riak has has been retired. We have to re-add it back.
• Other developers: N/A
• Release engineering: N/A
• Policies and guidelines:
  • We should promote officially Erlang Packaging Guidelines.

Upgrade/compatibility impact

Every Erlang upgrade requires the rebuilding of modules which contains ports or NIFs, and we will rebuild all such modules in Fedora. However if a user has some additional modules not available in a Fedora repository, then these modules must be rebuilt manually.

How To Test

• Ensure that high-grade Erlang applications are still working:

Name	Tested
couchdb	No
ejabberd	No
mochiweb	No
rabbitmq-server	No
riak	No (package was retired :( )
wings	No

• Collect feedback from volunteers regarding their experience with this Erlang/OTP version

User Experience

Users will get more robust, scalable, and fast Erlang applications.

Dependencies

The following packages must be rebuilt:

Name	Rebuilt
couchdb	No
ejabberd	No
erlang-basho_metrics	No
erlang-bitcask	No
erlang-cl	No
erlang-ebloom	No
erlang-eleveldb	No
erlang-emmap	No
erlang-erlsyslog	No
erlang-esasl	No
erlang-esdl	No
erlang-js	No
erlang-lfe	No
erlang-sd_notify	No
erlang-skerl	No
erlang-snappy	No
wings	No

Contingency Plan

• Contingency mechanism: None necessary. Instead of falling back to the previous version we should fix existing packages in order to help the Community. We should also monitor upstream development process for potentially discovered issues and proactively apply patches (as we already did with Erlang R14, Erlang R15, Erlang R16, Erlang 17, and Erlang 18). It should be noted that this change consists from an independent or loosely coupled smaller changes. If we fail to deliver some changes in time, we should reschedule these exact changes to the future Fedora release while keeping already implemented ones.
• Contingency deadline: N/A
• Blocks release? N/A
• Blocks product? N/A

Documentation

• Erlang/OTP 19.0 release notes

Release Notes

Erlang/OTP 19.0.1 is available in Fedora 25.