If logical replication slot is created with failover => true option, we
get respective field set to true in `pg_replication_slots` view.
By avoiding interacting with such slots we make logical failover slots
feature fully functional in PG17.
This commit is a breaking change:
1. `role` in DCS is written as "primary" instead of "master".
2. `role` in REST API responses is also written as "primary".
3. REST API no longer accepts role=master in requests (for example switchover/failover/restart endpoints).
4. `/metrics` REST API endpoint will no longer report `patroni_master`.
5. `patronictl` no longer accepts `--master` argument.
6. `no_master` option in declarative configuration of custom replica creation methods is no longer treated as a special option, please use `no_leader` instead.
7. `patroni_wale_restore` doesn't accept `--no_master` anymore.
8. `patroni_barman` doesn't accept `--role=master` anymore.
9. callback scripts will be executed with role=primary instead of role=master
10. On Kubernetes Patroni by default will set role label to primary. In case if you want to keep old behavior and avoid downtime or lengthy complex migrations you can configure `kubernetes.leader_label_value` and `kubernetes.standby_leader_label_value` to `master`.
However, a few exceptions regarding master are still in place:
1. `GET /master` REST API endpoint will continue to work.
2. `master_start_timeout` and `master_stop_timeout` in global configuration are still accepted.
3. `master` tag is still preserved in Consul services in addition to `primary`.
Rationale for these exceptions: DBA doesn't always 100% control the infrastructure and can't adjust the configuration.
- Fixed issues with has_permanent_slots() method. It didn't took into account the case of permanent physical slots for members, falsely concluding that there are no permanent slots.
- Write to the status key only LSNs for permanent slots (not just for slots that exist on the primary).
- Include pg_current_wal_flush_lsn() to slots feedback, so that slots on standby nodes could be advanced
- Improved behave tests:
- Verify that permanent slots are properly created on standby nodes
- Verify that permanent slots are properly advanced, including DCS failsafe mode
- Verify that only permanent slots are written to the `/status`
Create permanent physical replication slots on standby nodes and use `pg_replication_slot_advance()` function to move them forward.
The `restart_lsn` is advanced based on values stored in the `/status` key by the primary node.
When slot is created on a replica it could be ahead the same slot on the primary and therefore there is some period of time when it doesn't protect WAL files from being recycled.
Sometimes MacOS workers are so slow that Postgres shutdown might take more than 30s-40s, what breaks a test with replica reinit in parallel with the primary restart, because basebackup() does only two attempts and in a pause the replica remains running with empty PGDATA.
In addition to that increase timeouts in ignore_slots test.
Close#2637
keep as much backward compatibility as possible.
Following changes were made:
1. All internal checks are performed as `role in ('master', 'primary')`
2. All internal variables/functions/methods are renamed
3. `GET /metrics` endpoint returns `patroni_primary` in addition to `patroni_master`.
4. Logs are changed to use leader/primary/member/remote depending on the context
5. Unit-tests are using only role = 'primary' instead of 'master' to verify that 1 works.
6. patronictl still supports old syntax, but also accepts `--leader` and `--primary`.
7. `master_(start|stop)_timeout` is automatically translated to `primary_(start|stop)_timeout` if the last one is not set.
8. updated the documentation and some examples
Future plan: in the next major release switch role name from `master` to `primary` and maybe drop `master` altogether.
The Kubernetes implementation will require more work and keep two labels in parallel. Label values should probably be configurable as described in https://github.com/zalando/patroni/issues/2495.
There are sometimes good reasons to manage replication slots externally
to Patroni. For example, a consumer may wish to manage its own slots (so
that it can more easily track when a failover has a occurred and whether
it is ahead of or behind the WAL position on the new primary).
Additionally tooling like pglogical actually replicates slots to all
replicas so that the current position can be maintained on failover
targets (this also aids consumers by supplying primitives so that they
can verify data hasn't been lost or a split brain occurred relative to
the physical cluster).
To support these use cases this new feature allows configuring Patroni
to entirely ignore sets of slots specified by any subset of name,
database, slot type, and plugin.
