Improve PSQL wait script

[thatnerdjosh]

Follow up to #292

• Fix cleanup of connections while testing
• Migrate to pg_isready

[lathama]

Noting limits of the docker build process and best practices.

[thatnerdjosh]

@lathama - apologies for the back and forth - was struggling with the symlinks a bit.

This is ready for review :)

[thatnerdjosh]

@lathama - I don't think it's really ideal to maintain copy and paste of all those scripts, but I struggled to find a solution for that. I've ported all of the changes from the previous PR to all the new images

[lathama]

The installed package postgresql-client includes a tool called pg_isready which could be used to remove a ton of complexity. I had the cycles to take a look into this. The pg_isready could be added to the entrypoint.sh and the extra Python file could be removed.

$ pg_isready --help
pg_isready issues a connection check to a PostgreSQL database.

Usage:
  pg_isready [OPTION]...

Options:
  -d, --dbname=DBNAME      database name
  -q, --quiet              run quietly
  -V, --version            output version information, then exit
  -?, --help               show this help, then exit

Connection options:
  -h, --host=HOSTNAME      database server host or socket directory
  -p, --port=PORT          database server port
  -t, --timeout=SECS       seconds to wait when attempting connection, 0 disables (default: 3)
  -U, --username=USERNAME  user name to connect as

Report bugs to <pgsql-bugs@lists.postgresql.org>.
PostgreSQL home page: <https://www.postgresql.org/>

[thatnerdjosh]

Amazing - thank you @lathama - I'll migrate to this shortly

[thatnerdjosh]

@lathama - can you confirm if the below items are ok:

1. This returns 0 even in the case of failed authentication
2. There is no option to pass a DB password

This is fine if all we need to do is verify the DB is ready to accept connections, but seems less so if we want to validate a connection is actually established.

Please advise - thanks!

[thatnerdjosh]

Pending your feedback, I've completed the migration.

[lathama]

Looking now

[amh-mw]

See also #358, #394, #426 and #482.

Use cases:

1. permissive single-tenant: wait for postgres database, odoo startup creates odoo database, --db_name set, --no-database-list
2. permissive multi-tenant: wait for postgres database, use database manager to create database, --db_name unset
3. restrictive multi-tenant (multiple odoo servers, single database server): named database already created, use that database, --db_name set, --no-database-list

[thatnerdjosh]

@amh-mw - I've removed the DB_NAME override from this PR since the bulk of the changes was adding the pg_isready support. Once that is reviewed, I'll start working on the DB_NAME override :)

[codebykyle]

I know this PR is pretty old, but I will come out against removing the python file for pg_isready in the bash script.

The Python file allows us to use configparser to read the actual odoo.conf easily and connect to the databases listed.

While this can be accomplished via bash, Python has built-in native support for reading configuration files and also gives us access to logging libraries.

I have reworked the psql wait file to do this, although the changes are included as part of a broader change to how this library functions. See #538 and #539