2023-04-20: [GSTG] Patroni CI Cluster - Rename postgres_exporter schema to postgres_exporter_hidden. This is to help with the upcoming postgres major version upgrade

Stagin Change

Change Summary

Provide a high-level summary of the change and its purpose.

As outlined in https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/19280 during the Postgres major upgrade, we identified a schema compatibility issue – views in "postgres_exporter" causing errors like "column reference ..." . We have identified that there are two functions f_select_pg_stat_activity and f_select_pg_stat_replication are still used even after using the fully qualified names for pg_stat_activity, pg_stat_statements, pg_stat_wal_receiver - #8678 (comment 1348798444) With this change we are trying to rename postgres_exporter schema to postgres_exporter_hidden and fix any errors. Eventually, in a separate CR we will drop postgres_exporter_hidden schema

Reference

Change Details

  1. Services Impacted - List services
  2. Change Technician - @bshah11
  3. Change Reviewer - @NikolayS @alexander-sosna @rhenchen.gitlab
  4. Time tracking - 40 minutes
  5. Downtime Component - none

Detailed steps for the change

Change Steps - steps to take to execute the change

Estimated Time to Complete (mins) - Estimated Time to Complete in Minutes

  • Set label changein-progress /label ~change::in-progress
  • Identify gstg patroni Main cluster leader node and perform change on a leader node. 
     ssh patroni-ci-2004-01-db-gstg.c.gitlab-staging-1.internal "sudo gitlab-patronictl list"
  • Dump postgres_exporter schema as backup 
     /usr/lib/postgresql/12/bin/pg_dump   gitlabhq_production -h localhost -U gitlab-superuser  -s  -n postgres_exporter  > staging_issue_8755_postgres_exporter_schema.sql
  • Monitor postgres log for failed statements 
     sudo tail -f /var/log/gitlab/postgresql/postgresql.csv
  • Rename postgres_exporter schema to postgres_exporter_hidden 
     gitlab-psql -c "ALTER SCHEMA postgres_exporter RENAME TO postgres_exporter_hidden;"
  • Monitor postgres log for failed statements. 
     tail -f /var/log/gitlab/postgresql/postgresql.csv  | egrep -i "postgres_exporter|permission denied"
  • Grant select on pg_catalog.pg_stat_replication to postgres_exporter if you find errors in postgres log for pg_stat_replication 
     gitlab-psql -c "grant select on  pg_catalog.pg_stat_replication to postgres_exporter;"
  • Grant additional select permission on views to pg_read_all_stats if necessary to fix the errors observed in the postgres log 
     gitlab-psql -c "grant select on <Schema Name>.<View Name here> to postgres_exporter;"
  • Set label changecomplete /label ~change::complete

Rollback

Rollback steps - steps to be taken in the event of a need to rollback this change

Estimated Time to Complete (mins) - Estimated Time to Complete in Minutes

  • Revoke select on pg_catalog.pg_stat_replication from postgres_exporter 
     gitlab-psql -c "Revoke select on  pg_catalog.pg_stat_replication from postgres_exporter;"
  • It is not expected to continue to observer any errors for failed statements for the postgres_exorter queries. Rename postgres_exporter_hidden to postgres_exporter 
     gitlab-psql -c "ALTER SCHEMA postgres_exporter_hidden RENAME TO postgres_exporter;"
  • Set label changeaborted /label ~change::aborted

Monitoring

Key metrics to observe

Change Reviewer checklist

C4 C3 C2 C1:

  • Check if the following applies:
    • The scheduled day and time of execution of the change is appropriate.
    • The change plan is technically accurate.
    • The change plan includes estimated timing values based on previous testing.
    • The change plan includes a viable rollback plan.
    • The specified metrics/monitoring dashboards provide sufficient visibility for the change.

C2 C1:

  • Check if the following applies:
    • The complexity of the plan is appropriate for the corresponding risk of the change. (i.e. the plan contains clear details).
    • The change plan includes success measures for all steps/milestones during the execution.
    • The change adequately minimizes risk within the environment/service.
    • The performance implications of executing the change are well-understood and documented.
    • The specified metrics/monitoring dashboards provide sufficient visibility for the change.
      • If not, is it possible (or necessary) to make changes to observability platforms for added visibility?
    • The change has a primary and secondary SRE with knowledge of the details available during the change window.
    • The labels blocks deployments and/or blocks feature-flags are applied as necessary

Change Technician checklist

  • Check if all items below are complete:
    • The change plan is technically accurate.
    • This Change Issue is linked to the appropriate Issue and/or Epic
    • Change has been tested in staging and results noted in a comment on this issue.
    • A dry-run has been conducted and results noted in a comment on this issue.
    • The change execution window respects the Production Change Lock periods.
    • For C1 and C2 change issues, the change event is added to the GitLab Production calendar.
    • For C1 and C2 change issues, the SRE on-call has been informed prior to change being rolled out. (In #production channel, mention @sre-oncall and this issue and await their acknowledgement.)
    • For C1 and C2 change issues, the SRE on-call provided approval with the eoc_approved label on the issue.
    • For C1 and C2 change issues, the Infrastructure Manager provided approval with the manager_approved label on the issue.
    • Release managers have been informed (If needed! Cases include DB change) prior to change being rolled out. (In #production channel, mention @release-managers and this issue and await their acknowledgment.)
    • There are currently no active incidents that are severity1 or severity2
    • If the change involves doing maintenance on a database host, an appropriate silence targeting the host(s) should be added for the duration of the change.
Edited by Biren Shah