Switch 10.1, 10.2 and 10.3 to Stretch and switch to mariabackup

[klausenbusk]

• Switch 10.1, 10.2 and 10.3 to Stretch
• Add gnupg and dirmngr explicitly, as they are no longer installed
  as default.
• Add new MariaDB Signing Key [1]
• Drop xtrabackup from all image
• Install mariabackup in 10.1, 10.2 and 10.3
• Add procps explicitly, as it is needed by SST.
• Add mariabackup dependencies explicitly due to upstream bug:
  https://jira.mariadb.org/browse/MDEV-15869
• Ensure xtrabackup SST continue to work, so we don't break existing
  setups.
  Symlinks: xtrabackup -> mariabackup, xbstream -> mbstream
  Remove xtrabackup-v2 innobackupex version check
  innobackupex wrapper which start mariabackup with --innobackupex
  Tested on a 10.1 Galera setup with wsrep_sst_method="xtrabackup-v2"

[1] https://mariadb.com/kb/en/library/installing-mariadb-deb-files/#new-key

---

Should fix everything mentioned in #111

cc @tianon

[klausenbusk]

The failure seems unrelated, probably just a flaky keyserver..

[tianon]

Doesn't this imply that anywhere mariadb-backup isn't supported (like here in 10.0) that xtrabackup is also no longer installed and thus users will be broken? I don't think this is acceptable as-is, sorry.

It would also be great if we could get someone from MariaDB upstream to weigh in on whether this hacking of mariabackup to pretend it's xtrabackup is something they're willing to support (I like the idea conceptually, but it appears that it is not a 100% drop-in replacement from what's implemented here). 😅

[grooverdan]

@vaintroub want to add an official upstream comment here?

[vaintroub]

I cannot officially speak about what we're willing to support and what not, product management is for that . To give the perspective of mariabackup - it is basically parameter compatible with xtrabackup 2.3, just the home-made encryption is not supported, nor the tar streaming format. Unknown parameters are silently ignored, mariabackup inherited this ingenious feature from xtrabackup. There are no plans to make mariabackup command-line incompatible, and we'll try to fix the command-line incompatibilities. There should be no dependency on binary name either, so hacking to pretend should work fine, in most cases

[klausenbusk]

Doesn't this imply that anywhere mariadb-backup isn't supported (like here in 10.0) that xtrabackup is also no longer installed and thus users will be broken? I don't think this is acceptable as-is, sorry.

xtrabackup was added for Galera (10.1+) SST support and all xtrabackup -> mariabackup compatibility logic was done, so we don't break existing Galera setups which use xtrabackup for SST. So if decide to remove xtrabackup from <10.1, it won't break existing MySQL setups but only setup where xtrabackup is used for backups.

[grooverdan]

Additionally it looks like the plan is to make mariabackup-10.1 work with 10.0 and 5.5 (MDEV-14937, though MDEV-14176 is an outstanding issue for 5.5). When that happens can add mariabackup back into <10.1 if serving the backup functionality is required.