Expanding on the addition of docstrings in code, this adds python module API docs to sphinx documentation.
A developer can preview what this might look like by running this locally:
```
tox -m docs
```
The option `-W` is added to the tox env so that warning messages are considered errors.
Adds doc generation using the above method to the test GitHub workflow to catch documentation problems on PRs.
Some docstrings have been reformatted and fixed to satisfy errors generated with the above setup.
- the `_in_fligh` attribute is accessed from multiple threads and must be protected with mutex when it is changed
- allow adding tasks for `_in_fligh.group` from the `sync_pg_dist_node()` method when timeout is reached. Not doing so might result is indefinite transaction if REST API request from worker node failed.
- added pyrightconfig.json with typeCheckingMode=strict
- added type hints to all files except api.py
- added type stubs for dns, etcd, consul, kazoo, pysyncobj and other modules
- added type stubs for psycopg2 and urllib3 with some little fixes
- fixes most of the issues reported by pyright
- remaining issues will be addressed later, along with enabling CI linting task
* Ignore D401 in flake8-docstrings
* Fix newly reported flake8 issues, ignore the old W503 rule
* rely on concatenation of adjecent strings
* Format behave scripts
* Reformat ha.py according to new rules
Co-authored-by: Alexander Kukushkin <[email protected]>
We made incorrect assumption that `citus_set_coordinator_host()` will trigger `pg_dist_node` sync. Instead we should also use `citus_update_node()` and call `citus_set_coordinator_host()` only during the bootstrap.
Adjust behave tests to verify that coordinator failover is visible on workers.
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.
Citus cluster (coordinator and workers) will be stored in DCS as a fleet of Patroni logically grouped together:
```
/service/batman/
/service/batman/0/
/service/batman/0/initialize
/service/batman/0/leader
/service/batman/0/members/
/service/batman/0/members/m1
/service/batman/0/members/m2
/service/batman/
/service/batman/1/
/service/batman/1/initialize
/service/batman/1/leader
/service/batman/1/members/
/service/batman/1/members/m1
/service/batman/1/members/m2
...
```
Where 0 is a Citus group for coordinator and 1, 2, etc are worker groups.
Such hierarchy allows reading the entire Citus cluster with a single call to DCS (except Zookeeper).
The get_cluster() method will be reading the entire Citus cluster on the coordinator because it needs to discover workers. For the worker cluster it will be reading the subtree of its own group.
Besides that we introduce a new method get_citus_coordinator(). It will be used only by worker clusters.
Since there is no hierarchical structures on K8s we will use the citus group suffix on all objects that Patroni creates.
E.g.
```
batman-0-leader # the leader config map for the coordinator
batman-0-config # the config map holding initialize, config, and history "keys"
...
batman-1-leader # the leader config map for worker group 1
batman-1-config
...
```
Citus integration is enabled from patroni.yaml:
```yaml
citus:
database: citus
group: 0 # 0 is for coordinator, 1, 2, etc are for workers
```
If enabled, Patroni will create the database, citus extension in it, and INSERTs INTO `pg_dist_authinfo` information required for Citus nodes to communicate between each other, i.e. 'password', 'sslcert', 'sslkey' for superuser if they are defined in the Patroni configuration file.
When the new Citus coordinator/worker is bootstrapped, Patroni adds `synchronous_mode: on` to the `bootstrap.dcs` section.
Besides that, Patroni takes over management of some Postgres GUCs:
- `shared_preload_libraries` - Patroni ensures that the "citus" is added to the first place
- `max_prepared_transactions` - if not set or set to 0, Patroni changes the value to `max_connections*2`
- wal_level - automatically set to logical. It is used by Citus to move/split shards. Under the hood Citus is creating/removing replication slots and they are automatically added by Patroni to the `ignore_slots` configuration to avoid accidental removal.
The coordinator primary actively discovers worker primary nodes and registers/updates them in the `pg_dist_node` table using
citus_add_node() and citus_update_node() functions.
Patroni running on the coordinator provides the new REST API endpoint: `POST /citus`. It is used by workers to facilitate controlled switchovers and restarts of worker primaries.
When the worker primary needs to shut down Postgres because of restart or switchover, it calls the `POST /citus` endpoint on the coordinator and the Patroni on the coordinator starts a transaction and calls `citus_update_node(nodeid, 'host-demoted', port)` in order to pause client connections that work with the given worker.
Once the new leader is elected or postgres started back, they perform another call to the `POST/citus` endpoint, that does another `citus_update_node()` call with actual hostname and port and commits a transaction. After transaction is committed, coordinator reestablishes connections to the worker node and client connections are unblocked.
If clients don't run long transaction the operation finishes without client visible errors, but only a short latency spike.
All operations on the `pg_dist_node` are serialized by Patroni on the coordinator. It allows to have more control and ROLLBACK transaction in progress if its lifetime exceeding a certain threshold and there are other worker nodes should be updated.
