From Fedora Project Wiki

Better Erlang Integration

Summary

Update Erlang/OTP to R17, and i Erlang integration with the rest of Fedora.

Owner

Current status

  • Targeted release: Fedora 21
  • Last updated: 2014-03-23
  • Tracker bug: <will be assigned by the Wrangler>

Detailed Description

Erlang in Fedora is already in a good shape. However we can do better since there are a number of annoying shortcomings and issues. Just a few of them:

  • Fedora partially enabled Ellyptic Curve Crypto recently but we still provide Erlang with EC disabled completely because there is no way to enable just a few EC in the current Erlang version.
  • Erlang<->systemd interaction is in a quite poor state currently.
  • There is no way to install "headless" Erlang. Every Fedora Erlang user have to install graphical libraries even if (s)he doesn't want to use GUI on the target machine.
  • Every daemon written in Erlang has its own logging solution which doesn't use neither syslog nor Journald.
  • Erlang packaging is quite complex and undocumented mostly.

In order to address all these issues we should do the following:

  • Enable fine grained EC crypto support by upgrading Erlang to the latest R17 (not yet released, and scheduled to April, 2014).
  • Start working on a better systemd support in Erlang by enabling EPMD systemd support. This could be done by merging patches from Matwey V. Kornilov.
  • Add erlang-ejournald, erlang-lager_journald_backend, and make Journald as a default logging backend.
  • Split-off infrequently used modules which requires X11, Pulseaudio and ensure that it won't break anything.
  • Fix the long-standing noarch issue by providing additional default location for Erlang bytecode data.
  • Update Erlang RPM-related macros to improve packaging by reducing spec-file sizes.

Benefit to Fedora

  • Users will get initial EC support in Erlang. We still can't enable EC fully but at least we will enable some EC curves.
  • Users will have less issues caused by poor systemd and EPMD integration (lost node names during other Erlang daemons restarts etc).
  • Users will get centralized unified logging from all Erlang applications
  • Users won't have to install X11-related libraries if they don't want to.
  • Packagers won't see scary rpmlint messages regarding marking arch-independent package as arch-dependent one.
  • Packagers will spend less time on packaging Erlang software for Fedora.

Scope

  • Proposal owners:
    • We must rebuild Erlang R17 and submit it to build-overrides.
      • We have to rebuild all the packages listed below in the Dependencies section.
    • A necessary *.socket unit must be added to erlang-erts to enable EPMD socket activation.
      • Every Erlang daemon must require epmd.socket.
    • We need to fill new review request for erlang-ejournald
      • We have to fill new review request for erlang-lager_journald_backend
    • We have to patch out GUI parts and provide a way to tell user what to do in order to enable this functionality.
    • Add another default directory to look for Erlang *.beam files.
    • Every Erlang package must require erlang-rpm-macros.
  • Other developers: N/A
  • Release engineering: N/A
  • Policies and guidelines:
    • We should create Erlang Packaging Guidelines which doesn't exist yet.

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 (s)he will have to rebuild it manually.

How To Test

  • Ensure that high-grade Erlang applications are still working:
Name Tested
Package-x-generic-16.pngcouchdb No
Package-x-generic-16.pngejabberd No
Package-x-generic-16.pngmochiweb No
Package-x-generic-16.pngrabbitmq-server No
Package-x-generic-16.pngriak No
Package-x-generic-16.pngwings No
  • Collect feedback from volunteers regarding their experience with this Erlang/OTP version

User Experience

Fedora Erlang users will get more robust Erlang configurations. Less issues, more detailed logs.

Dependencies

The following packages must be rebuilt:

Name Rebuilt
Package-x-generic-16.pngcouchdb No
Package-x-generic-16.pngejabberd No
Package-x-generic-16.pngerlang-basho_metrics No
Package-x-generic-16.pngerlang-bitcask No
Package-x-generic-16.pngerlang-cl No
Package-x-generic-16.pngerlang-ebloom No
Package-x-generic-16.pngerlang-eleveldb No
Package-x-generic-16.pngerlang-emmap No
Package-x-generic-16.pngerlang-erlsyslog No
Package-x-generic-16.pngerlang-esasl No
Package-x-generic-16.pngerlang-esdl No
Package-x-generic-16.pngerlang-js No
Package-x-generic-16.pngerlang-skerl No
Package-x-generic-16.pngerlang-snappy No
Package-x-generic-16.pngwings No

Contingency Plan

  • Contingency mechanism: None necessary. This change consists from an independent or loosely coupled smaller changes. 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, and Erlang R16). 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

N/A (not a System Wide Change)

Release Notes

Erlang/OTP R17 with partial Ellyptic Curve Cryptography support is available in Fedora 21. This release also has better systemd integration, and more modularized structure.