pgb‐peers relation

This reference documentation details the implementation of the pgb-peers peer relation. This is the peer relation for pgbouncer, used to share user and config information from the leader unit to the follower units. The file implementing these relations can be found here: src/relations/peers.py.

Expected Interface

These are the expected contents of the databags in this relation (all values are examples, generated in a running test instance):

relation (id: 2)	pgbouncer-k8s
metadata
relation name	pgb-peers
interface	pgb_peers
leader unit	0
type	peer
application databag
auth_file	"pgbouncer_auth_relation_id_3" "md5aad46d9afbcc8c8248d254d567b577c1"
cfg_file	example pgbouncer config file
leader_hostname	pgbouncer-k8s-0.pgbouncer-k8s-endpoints.test-pgbouncer-provider-gnrj.svc…
relation_id_4	Z4OtFCe6r5HG6mk1XuR6LkwZ

Hook Handler Flowcharts

These flowcharts detail the control flow of the hooks in this program. Unless otherwise stated, a hook deferral is always followed by a return.

Peer Relation Created Hook

flowchart TD
  hook_fired([peer-relation-created Hook]) --> save_hostname[Save unit hostname  in unit databag]
  save_hostname --> is_leader{Is current unit leader?}
  is_leader -- no --> rtn([return])
  is_leader -- yes --> is_cfg{Is pgbouncer config available?}
  is_cfg -- no --> defer>defer]
  is_cfg -- yes --> update_cfg[Update config in peer databag]
  update_cfg --> is_backend_ready{Is backend database ready?}
  is_backend_ready -- no --> defer2>defer]
  is_backend_ready -- yes --> update_auth[Add auth file to secret store]
  update_auth --> rtn2([return])

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Peer Relation Changed Hook

flowchart TD
  hook_fired([peer-relation-changed Hook]) --> save_hostname[Save unit hostname  in unit databag]
  save_hostname --> update_relations[Update peer data  in relation databags]
  update_relations --> is_leader{Is current unit leader?}
  is_leader -- yes --> is_cfg{Is local pgbouncer config available?}
  is_cfg -- no --> defer>defer]
  is_cfg -- yes --> update_cfg[Update pgbouncer config and leader hostname  in app databag]
  update_cfg --> rtn([return])
  is_leader -- no --> is_cfg_in_databag{Is a valid config file in the app databag?}
  is_cfg_in_databag -- yes --> save_cfg[Save config from application databag]
  is_cfg_in_databag -- no --> is_auth_in_databag{Is a valid auth file in the app databag?}
  save_cfg --> is_auth_in_databag
  is_auth_in_databag -- yes --> save_auth[Save auth file from application databag]
  is_auth_in_databag -- no --> reload[if auth file or  config have changed, reload pgbouncer]
  save_auth --> reload
  reload --> rtn2([return])

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