Logical Replication

[Zvirovyi]

This is an implementation of the Logical Replication specification (On-Review): https://docs.google.com/document/d/1f84Z4cZwUD4q4bJsXTTC_PUaZr7pPB0Q6HnQ9cgCX_o/edit?usp=sharing.

Important

I cannot merge the latest postgresql-k8s lib revision therefore cannot create a new release because of the significant change made to this lib on the 14 channel, that prevents 16 channel from working when merged.

Basic testing

1. deploy postgresql and postgresql2
2. deploy two data-integrator charms with the database-name=testdb config and integrate them with the both of postgresql charms
3. establish logical replication relation: juju integrate postgresql:logical-replication-offer postgresql2:logical-replication
4. create testing table with data in the postgresql: create table asd (message text); insert into asd values ('hello');
5. create the same table (but empty) on the postgresql2 side
6. configure logical replication: juju config postgresql2 logical_replication_subscription_request='{"testdb": ["public.asd"]}'
7. check testing table on postgresql2 side: select * from asd;, and observe the data copied from the postgresql publisher
8. add another data to the testing table on postgresql side and observe it was pushed to the postgresql2 subscriber

[codecov]

Codecov Report

Attention: Patch coverage is 20.57971% with 274 lines in your changes missing coverage. Please review.

Project coverage is 66.01%. Comparing base (59e6ff2) to head (621c98b).

Files with missing lines	Patch %	Lines
src/relations/logical_replication.py	18.32%	250 Missing and 4 partials ⚠️
src/backups.py	37.50%	8 Missing and 2 partials ⚠️
src/charm.py	54.54%	3 Missing and 2 partials ⚠️
src/cluster.py	16.66%	5 Missing ⚠️

❌ Your patch check has failed because the patch coverage (20.57%) is below the target coverage (33.00%). You can increase the patch coverage or adjust the target coverage.
❌ Your project check has failed because the head coverage (66.01%) is below the target coverage (70.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff             @@
##           16/edge     #924      +/-   ##
===========================================
- Coverage    70.23%   66.01%   -4.22%     
===========================================
  Files           16       17       +1     
  Lines         3723     4067     +344     
  Branches       541      592      +51     
===========================================
+ Hits          2615     2685      +70     
- Misses         974     1240     +266     
- Partials       134      142       +8     

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