If communication with etcd nodes failed it is logical to start from scratch, from nodes that are listed in the config. But, it could happen that config is in fact outdated and all nodes in the real cluster were replaced.
Previously we used to track whether config file was changed, which turned out not to work in all possible cases.
The new strategy is a bit more different - if communication with all nodes failed we will continue keeping the last know topology and at the same time will try to figure out the new one by merging two lists together, the cached list and the list from the config file.
Configuration parameter is `kubernetes.retriable_http_codes` or `PATRONI_KUBERNETES_RETRIABLE_HTTP_CODES` environment variable.
These status codes are added to the default list of 500, 503, 504.
Close https://github.com/zalando/patroni/issues/2536
It could happen that Patroni is started up before PGDATA was mounted. In this case Patroni can't determine major Postgres version from PG_VERSION file. Later, when PGDATA is mounted, Patroni was trying to create the recovery.conf even if the actual Postgres major version is newver than 12.
To mitigate the problem we double check that the `Postgresql._major_version` is set before writing recovery configuration or starting postgres up.
Close https://github.com/zalando/patroni/issues/2434
Since a long time Patroni enforcing only one callback script running at a time. If the new callback is executed while the old one is still running, the old one is killed (including all child processes).
Such behavior is fine for all callbacks but on_reload, because the last one may accidentally cancel important ones, that for example updating DNS or assigning/removing Virtual IP.
To mitigate the problem we introduce a dedicated executor for on_reload callbacks, so that on_reload may only cancel another on_reload.
Ref: https://github.com/zalando/patroni/issues/2445
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.
When `synchronous_standby_names` GUC is changed PostgreSQL nearly immediately starts reporting corresponding walsenders as synchronous, while in fact they maybe didn't reach this state yet. To mitigate this problem we memorize current flush lsn on the primary right after change of `synchronous_standby_names` got visible and use it as an additional check for walsenders.
The walsender will be counted as truly "sync" only when write/flush/replay_lsn on it reached memorized LSN and the `application_name` is known to be a part of `synchronous_standby_names`.
The size of PR mostly related to refactoring and moving the code responsible for working with `synchronous_standby_names` and `pg_stat_replication` to the dedicated file.
And `parse_sync_standby_names()` function was mostly copied from #672.
1. Fix problem with logical slots not advancing when only the primary lost access to DCS
2. Don't let Patroni to join as a raft voting member when running failsafe behave tests. It allows to test exactly the same conditions as for other DCS
3. Speed up dcs_failsafe_mode behave tests by getting rid from long sleeps, slight reshuffling of places when we start/stop outage, and by killing Patroni/Postgres to avoid long shutdown due to the leader key removal attempts.
If enabled it will allow Patroni to cope with DCS outages.
In case of a DCS outage the leader tries to call all remaining members in the cluster via API and if all of them respond with success the leader will not be demoted.
The failsafe_mode could be enabled by running
```sh
patronictl edit-config -s failsafe_mode=true
```
or by calling the `/config` REST API endpoint.
Co-authored-by: Polina Bungina <[email protected]>
If the cluster is stable (no nodes are joining/leaving/lagging) we want to run at most one monitor query per every HA loop. So far it worker perfectly except when synchronous_mode is enabled, where we run two additional queries:
1. SHOW synchronous_mode
2. SELECT ... FROM pg_stat_replication
In order to solve it, we will include these "queries" to the common monitoring query is synchronous_mode is enabled.
In addition to that make sure that `synchronous_standby_names` is reset on replicas that used to be a primary and avoid using replicas which are not in the 'running' state.
P.S.: in the monitoring query we also extract the current value of synchronous_standby_names, because it will be useful for the quorum commit feature.
Close https://github.com/zalando/patroni/issues/2469
When doing the leader race we need to check that the former primary isn't alive anymore. For that we relied on non-inclusive terms. In order to simplify future work on getting rid from all non-inclusive words we change the check to rely on a difference in format of wal/xlog field. There is only "location" for the primary and "replayed_location" + "received_location" for standbys.
In addition to that we start supporting "wal" field as well as deprecated "xlog".
Co-authored-by: Polina Bungina <[email protected]>
There is a known [vector of attact](https://pganalyze.com/blog/5mins-postgres-security-patch-releases-pgspot-pghostile) by creating functions and/or operators in a public scheme with the same name and signature as corresponding objects in `pg_catalog`.
Since Patroni is heavily relying on superuser connections we want to mitigate it by enforcing `search_path=pg_catalog` for all connections created by Patroni (except replication connections). It is achieved by introducing a new function, that wraps psycopg.connect() and appends ` -c search_path=pg_catalog` to `options` parameter.
In addition to that, we set connection.autocommit to True before returning it.
Fix issue of patroni configuring watchdog with defaults when bootstrapping a new cluster rather than taking configuration used to bootstrap the DCS.
Also log changes to watchdog configuration based on calculated timeout value.
Close#2470
Previously such an exception was raised only from the `get_cluster()` method, and now we will to do the same from the `update_leader()` and `attempt_to_acquire_leader()` methods.
These methods influence Postgres promotion and demotion and we want to make a difference between different types of failures. Specifically, if calls have failed because DCS isn't accessible or due to a timeout.
This commit is extracted from the #2379
* Remove patronictl configure command
* Change name of the "secret" ENV variable (DCS->DCS_URL) and the corresponding patronictl option (to avoid mixing it up with the one from tests)
The only advantage of localkube was being a low weight. Anything else started creating only problems:
1. It is not properly maintained for many years.
2. It effectively worked only on Linux, but stopped on modern version due to changes in iptables.
Instead, we will use widely adoped tools like kind or k3s. The "kind-kind" is the default K8s context (see ~/.kube/config), but it could be overriden using `PATRONI_KUBERNETES_CONTEXT` environment variable. When executed from GH actions the context is set to k3d-k3s-default, because K3s is much faster to start.
The HAProxy is closing connections as soon as it got the HTTP Status code leaving no time for Patroni to properly shutdown SSL connection.
Close https://github.com/zalando/patroni/issues/2466
Windows doesn't support `SIGTERM`, but our behave tests in majority of cases relying on Patroni graceful shutdown.
In order to emulate the behaviour we introduced the new REST API endpoint `POST /sigterm`. The endpoint works only on Windows and when `BEHAVE_DEBUG` environment variable is set.
Besides that some minor adjustments in behave tests were done. Mainly related to backslash-slash handling.
In addition to that improve test coverage on Windows by properly mocking access to filesystem and avoiding calling
`subprocess.call()`. Specifically, symlink creation on Windows requires Admin privileges and there is no `true.exe`.
If cluster has a create replica method that does not require a leader it can get triggered while bootstrap is running. If that method comes up with an accessible cluster faster than the bootstrap completes it will get promoted as the leader, only to lose leader lock when bootstrap completes. To fix this we only consider leaderless create replica methods if sysid is non-empty, i.e. there is no bootstrap running.
- We use `failover.leader` check as an indicator of switchover. The check on `failover.candidate` was unnecessary and incorrect.
- Add more unit-tests for switchover in sync mode
Close https://github.com/zalando/patroni/issues/2405
Co-authored-by: Polina Bungina <[email protected]>
On busy clusters with many logical replication slots the pg_replication_slot_advance () call affects the main HA loop and could result in the member key expiration.
The only way to solve it is a dedicated thread response for moving slots forward.
The thread is started only when there are logical slots to be advanced.
Will help to solve #2388Close#2239
There is currently a risk to lose some WAL segments entirely in case
archive_mode was set to 'on' before a promotion and there are some WALs
with .ready files on the former leader we are trying to rewind. It happens
because of the pg_rewind's modus operandi: it simply syncs the content of
pg_wal directory of the old leader with the new leader's one. Including
deletion of all WALs that are not present on the current leader, regardless
their archive status on the former one. Thus, in case the new leader has
already recycled such files, we just remove them entirely.
In case archive_mode was set to 'always' and the .ready WALs are acrually
present in archive, it is for end user who writes the archive_command to
avoid overwritting and to properly test it.
Co-authored-by: Alexander Kukushkin <[email protected]>
If replication slots are enabled Patroni automatically creates them for any cluster member that is supposed to stream from a given node and for any permanent slot defined in the global configuration. If the member disappears from the DCS Patroni automatically removes the replication slot for it. The same behavior was in the maintenance mode (pause).
This commit disables removal of any replication slots that don't match Patroni's expectations in pause.
Close https://github.com/zalando/patroni/issues/2314
