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Erlang 19

Summary

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

Owner

Current status

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 (19.0.2). Done!
    • We must rebuild every package which requires NIF version (listed below in the Dependencies section) against Erlang 19.x.y. THis time Erlang uses the same Driver version API/ABI as in a previous release so driver libraries rebuild isn't necessary. Done!
    • Upgrade erlang-rebar to the recently released version 2.6.2 and rebase/drop unneeded patches. Done.
    • Make Erlang RPM build macros more consistent with Golang RPM macros.
    • Every Erlang daemon's systemd unit should require epmd.socket.
    • Consider allowing EPMD implementation switching. Erlang is about choice!
    • We need to fill new review request for erlang-ejournald
    • 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:

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
elixir No
mochiweb No
rabbitmq-server No
riak No (package was retired :( )
tsung No
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 Yes
erlang-basho_metrics Yes
erlang-bitcask Yes
erlang-cl Yes
erlang-ebloom Yes
erlang-eleveldb Yes
erlang-emmap Yes
erlang-erlsyslog n/a
erlang-esasl n/a
erlang-esdl n/a
erlang-esip Yes
erlang-fast_tls Yes
erlang-fast_xml Yes
erlang-fast_yaml Yes
erlang-iconv Yes
erlang-jiffy Yes
erlang-js n/a
erlang-lfe n/a
erlang-riak_ensemble Yes
erlang-sd_notify Yes
erlang-skerl Yes
erlang-snappy Yes
erlang-stringprep Yes
wings n/a

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

Release Notes

Erlang/OTP 19.0.2 is available in Fedora 25.

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