How other snaps can use PostgreSQL snap via slots?

[troyanov]

Hello folks,

I was trying to reuse psql (since now bins are exposed via slots #44)

Here is the plug from my snap:

plugs:
  postgresql:
    interface: content
    content: bins
    target: $SNAP/opt/postgresql

The very first attempt failed:

$SNAP/opt/postgresql/usr/bin/psql
Can't locate PgCommon.pm in @INC (you may need to install the PgCommon module) (@INC contains: /etc/perl /usr/local/lib/x86_64-linux-gnu/perl/5.34.0 /usr/local/share/perl/5.34.0 /usr/lib/x86_64-linux-gnu/perl5/5.34 /usr/share/perl5 /usr/lib/x86_64-linux-gnu/perl-base /usr/lib/x86_64-linux-gnu/perl/5.34 /usr/share/perl/5.34 /usr/local/lib/site_perl) at /snap/app/x1/opt/postgresql/usr/bin/psql line 22.
BEGIN failed--compilation aborted at /snap/app/x1/opt/postgresql/usr/bin/psql line 22.

Setting the env for Perl helps a bit PERL5LIB=$SNAP/opt/postgresql/usr/share/perl5:$PERL5LIB
But then I hit another error:

$SNAP/opt/postgresql/usr/bin/psql -h 127.0.0.1
Error: You must install at least one postgresql-client-<version> package

I am curious if you can give some hints on how it should be used?

[syncronize-issues-to-jira]

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The internal ticket has been created: https://warthogs.atlassian.net/browse/DPE-8890.

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[dragomirp]

Hi, cross posting from the Matrix discussion:

Hi, sorry for the delay. Here's an example snap repo: https://github.com/dragomirp/test-snap. There are two ways to approach this:

• Call the psql binary directly (located in bins mountpoint /usr/lib/postgresql/16/bin/psql) then you only need to set LD_LIBRARY_PATH to include so dependencies binary dependencies for psql, but you'll need to find the correct version in the plug connected hook (what the perl pg_wrapper script does)
• Wire the perl wrapper, binary dependencies and mount /usr/lib/postgresql within the client snap, so that the perl script can figure out which versions are available. AFAIK the easiest way to do that is use snap connect hook and setup the directory structure in a writable location (I used $SNAP_DATA in the example)

If you want to re-expose psql as an application, you'll need a wrapper script, since it may or may not be available, depending on if the plug is connected.

[troyanov]

Thanks a lot for the example @dragomirp so it appears to be a bit more complicated than I thought. I was hoping that just connecting the plug would work.