I personally have always enjoyed the Ubuntu Developer Summits (UDS), but nowadays they have been converted to the Ubuntu Online Summits (UOS). Attending them is not always convenient (timezone issues, might be travelling, etc.) so I watched the recorded video of a session I was interested in: MySQL & Variants in 16.04.

My key takeaways

1. Ubuntu 16.04 Xenial Xerus is an LTS release.
2. The term “cross-grade” is used a lot (it is not about downgrading/upgrading, but being able to use MySQL or MariaDB or Percona Server interchangeably)
3. It would be nice to see MySQL 5.7 in this release (for Xenial as well as Debian Stretch). From Oracle there is a new packager taking over the task (Lars)
4. MySQL 5.5 is still the default in Debian, and there needs to be upgrades tested between 5.5 to 5.7 (it looks like the ideal jump is that Ubuntu will not be seeing MySQL 5.6)
5. Percona Server 5.7 is 60-90 days out; xtrabackup has had some new modifications and deserves an upgrade
6. Boost is a new requirement for MySQL 5.7 & Percona Server 5.7; some old TokuDB problems in the builds are likely already fixed in MariaDB Server so this can be inherited
7. MariaDB is waiting to iron out the bugs in 10.0, and may stick to that

My “raw” transcribed notes

• Attendees:

  • Jon Grimm (Engineering Director for Ubuntu)
  • Robie Basak (Ubuntu)
  • Otto Kekäläinen (MariaDB Foundation)
  • Lars Tangvald, Norvald H. Ryeng (Oracle)
  • George Ormond Lorch III (Percona)

• Robie: Waiting in Debian for a transition slot from MySQL 5.5 to MySQL 5.6. There’s some discussion with bugs, re: Akonadi, need to also resolve ABI issues with MySQL 5.6. Not really discussed MySQL 5.7 yet.

• Norvald: 5.7, changes to installation. Client library ABI cleaned up. There may be some clients breaking because of that. No more exported symbols. See: The Client Library, Part 1: The API, the Whole API and Nothing but the API & The Client Library, Part 2: The Version Number
• mysql_install_db is now replaced by --initialize in the server, so have to rewrite the post-install scripts. Might also have some AppArmour changes. Spoke to people @ DebConf (so best place is to put AppArmour profiles upstream (i.e. in mysql) and Debian and other distros will get it from there). AppArmour profile is in the MySQL source package now. Probably can get away with doing everything as cmake variables.
• MySQL 5.7 has disabled the old password hashing algorithm, so if people haven’t upgraded they might have problems; so a manual intervention to fix their accounts.
• Going from MySQL 5.7 to MySQL 5.6? It is done by dump and restore. There is no testing automated downgrades. Are there disk format changes? Norvald is not aware of any. If you use virtual columns in 5.7, you can’t downgrade easily to 5.6.
• Robie would prefer to not release 5.6 and 5.7 concurrently. During Trusty, there was some level of user confusion. Debian – release team would prefer to see one transfer than two, so is it better to just do a single transition to 5.7?
• Norvald says there hasn’t been testing from 5.5 -> 5.7. They only support upgrades from 5.5 -> 5.6 -> 5.7. For Ubuntu the choice can be to have 5.6 and then later do 5.7, but Jessie only just released with 5.5, so Stretch with 5.6 might not be a great idea (so users migrating from Jessie to Stretch will go from 5.5 to 5.7). Could also have 5.7 depend on a stripped 5.6 binary (like the embedded server; this is for localhost and the security team shouldn’t be too annoyed) for people to do an upgrade. Norvald says this has not been tried and there needs to be a migration path tested from 5.5 -> 5.7.
• Conclusion: 5.7 in Stretch. Xenial is an LTS release, and 5.7 should be targeted for that.
• If the maintainer script fails (postinstall script fails – don’t leave apt in a weird state). If it fails then upgrades, leave a debconf critical notice to say that the service is disabled and then fix it manually. Otto says that leaving /etc in a broken state is terrible, so we should avoid it.
• Do we (Oracle) have the resources for 5.7 packaging and how soon can it be done in time for Xenial? There were patches from Lars in the git tree, but there haven’t been more recently. Lars will take over the 5.7 transition so if there is a list of work items, this will be settled (Lars will take over from Norvald).
• There will be a separate session with Norvald/Lars/Robie outside of UOS about 5.7. Defer the Boost conversation after the session as well.
• George: Percona is mainly looking out towards the 5.7 work and what kind of resources that will be put to that. There are new folk @ Percona to help with this. Percona inherits so much from the upstream codebase, it just works for Percona Server. There is Percona XtraDB Cluster and Percona xtrabackup, and xtrabackup has moved on quite a bit since the last upload (since last November 2014). So might be good idea to look at a refresh. There has also been a lot of work done on Percona XtraDB Cluster and there are some developments with Codership, so they are unsure if they will have their own Percona XtraDB Cluster 5.7 by the time Ubuntu is supposed to ship. When Percona is ready for something, just give Robie a shout to ensure that things happen. 60-90 days before a Percona Server 5.7 release. Just be aware of feature freeze for Xenial.
• Norvald mentions that Percona Server 5.7 will also depend on Boost and there needs to be a decision on this. George mentions that TokuDB is now part of Percona Server, and it has some of its own requirements as well. Do we include TokuDB? It has requirements like it will only run on 64-bit platforms. Things to figure out going forward? MariaDB has been carrying TokuDB last November, but Robie remembers disabling it in Ubuntu. George says there were some licensing issues back then but they seem to be taken care of.
• Otto says the builds for TokuDB was failing. It has a dependency on jemalloc, and that might have been the reason there were failures (says George). There may be something else where it doesn’t build on Ubuntu builders. But Otto says that there was a commit where this got fixed about last month. George will follow on, just to absorb it, since the legwork is already complete.
• Otto: Trusty has 5.5, and Jessie and all other Ubuntu releases have 10.0, and 10.1 was released last month and I’m not quite pushing it to Debian quite yet. Fix 10.0 build fixes, upstream them, then only focus on 10.1. Blocking? (last summer) 5.6 is not in testing, so could not depend on it/changes done in 5.6 mysql-common. Here’s hoping that mysql-common going forward will be generated separately.
• Robie will take an action to resolve the delta (probably just drop it). To sync MariaDB 10.0 to Xenial.
• Discussion on /var/lib/mysql/*.flag thing on the list — conclusion at: mailing list — goal: within a single Ubuntu release, people can “cross-grade” between MySQL variants. The goal is to support all 3, and users want to try them, and thats when the bug reports come. Robie’s goal: move to a per-variant data directory. Otto says that once directory names change, 3rd party tools might have breakage. So a working prototype. Migration path is difficult. Maybe the best is to turn /var/lib/mysql into a symlink and store the data elsewhere. PostgreSQL does per version directories today; so studying that is going to happen.