Initial Meilisearch Support

[majst01]

implements #47

TODO:

• create a dump before the upgrade with a copy of the previous binary. This solves the burden to have a high backup frequency in order to not loose data during a upgrade
• put dumps directly into the backup volume, start meilisearch with --dump-dir pointing to the extra backup volume to save additional copy and duplicate data in the datadir

[majst01]

Integration fails now because initially test timeout was set to 10m, raised it to 20m to make it pass, but a better approach would be to make a matrix job which iterates over database and restore/upgrade

[Gerrit91]

Thanks for taking this effort, I know it's cumbersome. Looking forward to get this running!

[Gerrit91]

During @majst01 vacation, I took over this PR. 😅

I applied the following changes now:

• Copying the old meilisearch binary after a backup and use this older version during the upgrade procedure, which now goes "start with old binary" -> "create a dump" -> "import with current binary" -> "done" (similar to Postgres upgrade)
• Stabilized the tests (integration tests take ~7m now, which I think is ok)
  • Longer probe timeouts as the wait process in the database pod was killed by K8s all the time, switching into exponential crash loop, which caused delays in the tests
  • Started the "helper databases" on Port 1 in order to prevent the wait process to assume that Meilisearch is already running during the restoration / upgrade
• Proper usage of db-path and dump-dir to avoid a lot of path handling in the implementation
• Moved example generation out of the tests into the Makefile, as well as added a start-meilisearch target for dev purposes
• Rollback after failed recovery attempt in order not to start with empty database

Still need to think about all the error handling one more time.

[vknabel]

is this too broad? Would 755 or something similar be enough?

[Gerrit91]

Probably yes, but there are many other places where same permissions are used. Maybe we should create a separate PR and address this.