Sharing a single connection between REST API and the main thread (doing heartbeats) was working mostly fine, except when Postgres becomes so slow that REST API queries start blocking the main loop.
If the dedicated REST API connection isn't available we use the heartbeat connection as a fallback.
* Use virtualenv to install tox in behave Dockerfile
Upstream change in postgres docker image uses debian restriction on
installing system-wide non-debian python packages. Debian doesn't
provide a tox>=4, so we need to install with pip.
* Exclude all output directories generated using `tox-wrapper.sh`
The `tox-wrapper.sh` script created by `features/Dockerfile` creates
directories like features/output-tox-pg14-docker-behave-etcd-lin-973719674/
* Reduce footprint of tox behave docker image
When running with the leader lock Patroni was just setting the `role` label to `master` and effectively `kubernetes.standby_leader_label_value` feature never worked.
Now it is fixed, but in order to not introduce breaking changes we just update default value of the `standby_leader_label_value` to the `master`.
`patronictl` is implemented using `click` module, and that module uses the functions' docstrings for creating a helper text.
As a consequence the docstring for `ctl` function was being shown to the user, which doesn't make sense.
This PR fixes that issue by adding a user-friendly description to be shown on `patronictl --help`. We use a `\f` to tell `click` when to stop capturing text to show in the helper.
Note that `patronictl` commands are implemented using `@ctl.command` decorator, and we always provide them with `help` argument. That said, none of the subcommands are affected by the aforementioned issue, only the entry point of the CLI.
References: PAT-201.
1.0.3 removed support of `top_level` configuration parameter and builds
now are failing.
Besides that remove redundant pyyaml from requirements.docs.txt
Make it hold connection kwargs for local connections and all `NamedConnection` objects use them automatically.
Also get rid of redundant `ConfigHandler.local_connect_kwargs`.
On top of that we will introduce a dedicated connection for the REST API thread.
The same (almost) logic was used in three different places:
1. `Patroni` class
2. `Member` class
3. `_MemberStatus` class
Now they all inherit newly intoduced `Tags` class.
* Add failsafe_mode_is_active to /patroni and /metrics
* Add patroni_primary to /metrics
* Add examples showing that failsafe_mode_is_active and cluster_unlocked
are only shown for /patroni when the value is "true"
* Update /patroni and /config examples
Cluster.get_replication_slots() didn't take into account that there can not be logical replication slots in a standby cluster replicas. It was only skipping logical slots for the standby_leader, but replicas were expecting that they will have to copy them over.
Also on replicas in a standby cluster these logical slots were falsely added to the `_replication_slots` dict.
1. stop using the same cursor all the time, it creates problems when not carefully used from different threads.
2. introduce query() method in the Connection class and make it return a result set when it is possible.
3. refactor most of the code that is relying (directly or indirectly) on the Connection object to use the query() method as much as possible.
This refactoring helps with reducing code complexity and will help with future introduction of a separate database connection for the REST API thread. The last one will help to improve reliability when system is under significant stress when simple monitoring queries are taking seconds to execute and the REST API starts blocking the main thread.
Previous to this commit `IntValidator` would always consider the value `0` invalid, even if in the allowed range.
The problem was that `parse_int` was returning `0` in the following line:
```python
value = parse_int(value, self.base_unit) or ""
```
However the `or ""` was evaluating to an empty string.
As `parse_int` returns either an `int` if able to parse, or `None` otherwise, the `isinstance(value, int)` is enough to error out when not a valid `int`.
Closes#2817
Besides adding docstrings to `patroni.config`, a few side changes
have been applied:
* Reference `config_file` property instead of internal attribute
`_config_file` in method `_load_config_file`;
* Have `_AUTH_ALLOWED_PARAMETERS[:2]` as default value of `params`
argument in method `_get_auth` instead of using
`params or _AUTH_ALLOWED_PARAMETERS[:2]` in the body;
* Use `len(PATRONI_ENV_PREFIX)` instead of a hard-coded `8` when
removing the prefix from environment variable names;
* Fix documentation of `wal_log_hints` setting. The previous docs
mentioned it was a dynamic setting that could be changed. However
it is managed by Patroni, which forces `on` value.
References: PAT-123.
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.
Due to historical reasons (not available before 9.6) we used `pg_current_wal_lsn()`/`pg_current_xlog_location()` functions to get current WAL LSN on the primary. But, this LSN is not necessarily synced to disk, and could be lost if the primary node crashed.
It seems that a common pitfall for new users of Patroni is that the `bootstrap.dcs` section is only used to initialize the configuration in DCS. This moves the comment about this to an info block so it is more visible to the reader.
New patroni.py option that allows to
* generate patroni.yml configuration file with the values from a running cluster
* generate a sample patroni.yml configuration file
* Refactor is_failover_possible()
Move all the members filtering inside the function.
* Remove check_synchronous parameter
* Add sync_mode_is_active() method and user it everywhere where it is appropriate
* Reduce nesting
---------
Co-authored-by: Alexander Kukushkin <[email protected]>
consider the scenario(enable failsafe_mode):
0. node1(primary) - node2(replica)
1. stop all etcd nodes; wait ttl seconds; start all etcd nodes; (node2's failsafe will contain the info about node1)
2. switchover to node2; (node2's failsafe still contain the info about node1)
3. stop all etcd nodes; wait ttl seconds; start all etcd nodes;
4. node2 will demote because it consider node1 as primary
Resetting failsafe state when running as a primary fixes the issue.
1. Unit tests should not really try accessing any resources.
2. Not doing so results in significant execution time of unit tests on Windows
In addition to that perform a request with timeout 3s. Usually this is more than enough to figure out whether resource is accessible.
Followup on #2724
This PR is an attempt of refactoring the docs about migration to Patroni.
These are a few enhancements that we propose through this PR:
* Docs used to mention the procedure can only be performed in a single-node cluster. We changed that so the procedure considers a cluster composed of primary and standbys;
* Teach how to deal with pre-existing replication slots;
* Explain how to create the user for `pg_rewind`, if user intends to enable `use_pg_rewind`.
References: PAT-143.
Postgres supports two types of permissions:
1. owner only
2. group readable
By default the first one is used because it provides better security. But, sometimes people want to run a backup tool with the user that is different from postgres. In this case the second option becomes very useful. Unfortunately it didn't work correctly because Patroni was creating files with owner access only permissions.
This PR changes the behavior and permissions on files and directories that are created by Patroni will be calculated based on permissions of PGDATA. I.e., they will get group readable access when it is necessary.
Close#1899Close#1901
The docs of `slots` configuration used to have this mention:
```
my_slot_name: the name of replication slot. If the permanent slot name
matches with the name of the current primary it will not be created.
Everything else is the responsibility of the operator to make sure that
there are no clashes in names between replication slots automatically
created by Patroni for members and permanent replication slots.
```
However that is not true in the sense that Patroni does not check for
clashes between `my_slot_name` and the name of replication slots created
for replicating changes among members. If you specify a slot name that
clashes with the name of a replication slot used by a member, it turns
out Patroni will make the slot permanent in the primary even if the member
key expire from the DCS.
Through this commit we also enhance the docs in terms of explaining that
physical permanent slots are maintained only in the primary, while logical
replication slots are copied from primary to standbys.
Signed-off-by: Israel Barth Rubio <[email protected]>
The node `postgresql2` in the repository is apparently supposed
to be a cascading standby.
However, if that is the case, there is a typo in the name of its
upstream node.
This commit fixes that issue.
In issue #2735 it was discussed that there should be some warning around PostgreSQL parameters that do not pass validation.
This commit ensures something is logged for parameters that fail validation and therefore fall back to default values.
Close#2735Close#2740
Consider a following situation:
1. node1 is stressed so much that Patroni heart-beat can't run regularly and the leader lock expires.
2. node2 notice that there is no leader, gets the lock, promotes, and gets to a situation like it is described in 1.
3. Patroni on node1 finally wakes up, notice that Postgres is running as a primary, but without a leader lock and "happily" acquires the lock.
That is, node1 discarded promoting of node2, and the node2 after that it will not be possible to join the node2 back to the cluster, because pg_rewind is not possible when two nodes are on the same timeline.
To partially mitigate the problem we introduce an additional timeline check. If postgres is running as primary Patroni will consider it as a perfect candidate only if timeline isn't behind the last known cluster timeline recorder in the `/history` key. If postgres timeline is behind the cluster timeline postgres will be demoted to read-only. Further behavior would depend on `maximum_lag_on_failover` and `check_timeline` settings.
Since the `/history` key isn't updated instantly after promotion, there is still a short period of time when the issue could happen, but it seems that it is close to impossible to make it more reliable.
Close https://github.com/zalando/patroni/issues/2779
It was reported in #2779 that the primary was constantly logging messages like `Synchronous replication key updated by someone else`.
It happened after Patroni was stuck due to resource starvation. Key updates are performed using create_revision/mod_revision field, which value is taken from the internal cached. Hence, it is a clear symptom of stale cache.
Similar issues in K8s implementation were addressed by invalidating the cache and restarting watcher connections every time when update failed due to resource_version mismatch, so we do the same for Etcd3.
On Slack user reported that Patroni didn't run pg_rewind on one of the nodes after coming out of maintenance mode.
Steps that were executed:
0. The initial state: node1 - primary, node2 - replica
1. `patronictl pause`
2. On node2: pg_ctl promote
3. On node1: pg_ctl stop
4. Patroni on node1 notice that Postgres isn't running and removes the leader lock
5. Patroni on node2 notice that Postgres is running as a primary and takes the leader lock.
6. `patronictl resume`.
After that node1 started saying in logs:
`Waiting for checkpoint on node2 before rewind`.
Repeating this steps may not necessarily reproduce the problem, because presumably pg_rewind failed earlier on node1.
Such situation was possible because promote wasn't executed by Patroni and therefore `Rewind._state` wasn't explicitly reset and the code that ensures that CHECKPOINT after promote was run wasn't triggered.
As a mitigation following changes have been made:
1. retrigger pg_rewind checks after coming out of maintenance mode
2. run ensure CHECKPOINT after promote checks using `Rewind._state != REWIND_STATUS.CHECKPOINT` condition. It allowed to remove useless hook from `Postgresql.promote()`.
When we don't have permanent logical slots Patroni was updating the `/status` on every heart-beat loop even when LSN on the primary isn't moving forward.
The issue was introduced in the #2485
