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.
* 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)
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`.
* update release notes
* bump version
* change the default alignment in patronictl table output to `left`
* add missing tests
* add missing pieces to the documentation
The only python-etcd3 client working directly via gRPC still supports only a single endpoint, which is not very nice for high-availability.
Since Patroni is already using a heavily hacked version of python-etcd with smart retries and auto-discovery out-of-the-box, I decided to enhance the existing code with limited support of v3 protocol via gRPC-gateway.
Unfortunately, watches via gRPC-gateway requires us to open and keep the second connection to the etcd.
Known limitations:
* The very minimal supported version is 3.0.4. On earlier versions transactions don't work due to bugs in grpc-gateway. Without transactions we can't do atomic operations, i.e. leader locks.
* Watches work only starting from 3.1.0
* Authentication works only starting from 3.3.0
* gRPC-gateway does not support authentication using TLS Common Name. This is because gRPC-proxy terminates TLS from its client so all the clients share a cert of the proxy: https://github.com/etcd-io/etcd/blob/master/Documentation/op-guide/authentication.md#using-tls-common-name
$ python3 patronictl.py -c postgresql0.yml list
Error: Provided config file postgresql0.yml not existing or no read rights. Check the -c/--config-file parameter
That required a refactoring of `Config` and `Patroni` classes. Now one has to explicitely create the instance of `Config` before creating `Patroni`.
The Config file can optionally call the validate function.
We will try to import only the module which has a configuration section.
I.e. if there is only zookeeper section in the config, Patroni will try to import only `patroni.dcs.zookeeper` and skip `etcd`, `consul`, and `kubernetes`.
This approach has two benefits:
1. When there are no dependencies installed Patroni was showing INFO messages `Failed to import smth`, which looks scary.
2. It reduces memory usage, because sometimes dependencies are heavy.
The /history endpoint shows the content of the `history` key in DCS
The /cluster endpoint show all cluster members and some service info like pending and scheduled restarts or switchovers.
In addition to that implement `patronictl history`
Close#586Close#675Close#1133
* make it possible to use client certificates with REST API
* define a separate PatroniRequest class which handles all communication
* refactor patronictl to use the new class
* make Ha to use the new class instead of calling requests.get. The old call wasn't taking into account certificates and basic-auth
Close#898
We are using only one function from there, `find_executable()` and it is better to implement a similar function in Patroni rather than add `distutils` module into requirements.txt
* Convert postgresql.py into a package
* Factor out cancellable process into a separate class
* Factor out connection handler into a separate class
* Move postmaster into postgresql package
* Factor out pg_rewind into a separate class
* Factor out bootstrap into a separate class
* Factor out slots handler into a separate class
* Factor out postgresql config handler into a separate class
* Move callback_executor into postgresql package
This is just a careful refactoring, without code changes.
* Use `shutil.move` instead of `os.replace`, which is available only from 3.3
* Introduce standby-leader health-check and consul service
* Improve unit tests, some lines were not covered
* rename `assertEquals` -> `assertEqual`, due to deprecation warning
Implementation of "standby cluster" described in #657. Standby cluster consists
of a "standby leader", that replicates from a "remote master" (which is not a
part of current patroni cluster and can be anywhere), and cascade replicas,
that replicate from the corresponding standby leader. "Standby leader" behaves
pretty much like a regular leader, which means that it holds a leader lock in
DSC, in case if disappears there will be an election of a new "standby
leader".
One can define such a cluster using the section "standby_cluster" in patroni
config file. This section provides parameters for standby cluster, that will be
applied only once during bootstrap and can be changed only through DSC.
* Use scope from config file when listing members
* Add version command to patronictl
* Only delete leader on shutdown when we have the lock to avoid exceptions when leader key does not exist
* Add a timestamp option to list command.
* YAML format for patronictl output
* Fix API request to get version
Make it possible to cancel a running task if you want to reinitialize replica.
There are two possible ways to trigger it:
1. patronictl will ask whether you want to cancel already running task if an attempt to trigger reinitialize has failed
2. if you are using `--force` argument with `patronictl reinit`
* Show information about scheduled failover and maintenance mode when showing list of cluster members. Fixes https://github.com/zalando/patroni/issues/557
* Fix postgres version check functions (postgres 10 and above compatibility) and apply pep8 formatting to the tests.
* Bump some configuration parameters to match with postgres 10 defaults.
* Fix name of contributor in release notes.
Current UI to change cluster configuration is somewhat unfriendly, involving a curl command, knowing the REST API endpoint, knowing the specific syntax to call it with and writing a JSON document. I added two commands in this branch to make this a bit easier, `show-config` and `edit-config` (names are merely placeholders, any opinions on better ones?).
* `patronictl show-config clustername` fetches the config from DCS, formats it as YAML and outputs it.
* `patronictl edit-config clustername` fetches the config, formats it as YAML, invokes $EDITOR on it, then shows user the diff and after confirmation applies the changed config to DCS, guarding for concurrent modifications.
* `patronictl edit-config clustername --set synchronous_mode=true --set postgresql.use_slots=true` will set the specific key-value pairs.
There are also some UI capabilities I'm less sure of, but included them here as I already implemented them.
* If output is a tty then the diffs are colored. I'm not sure if this feature is cool enough to pull the weight of adding a dependency on cdiff. Or maybe someone knows of another more task focused diff coloring library?
* `patronictl edit-config clustername --pg work_mem=100MB` - Shorthand for `--set postgresql.parameters.work_mem=100MB`
* `patronictl edit-config clustername --apply changes.yaml` - apply changes from a yaml file.
* `patronictl edit-config clustername --replace new-config.yaml` - replace config with new version.
Previously pg_ctl waited for a timeout and then happily trodded on considering PostgreSQL to be running. This caused PostgreSQL to show up in listings as running when it was actually not and caused a race condition that resulted in either a failover or a crash recovery or a crash recovery interrupted by failover and a missed rewind.
This change adds a master_start_timeout parameter and introduces a new state for the main run_cycle loop: starting. When master_start_timeout is zero we will fail over as soon as there is a failover candidate. Otherwise PostgreSQL will be started, but once master_start_timeout expires we will stop and release leader lock if failover is possible. Once failover succeeds or fails (no leader and no one to take the role) we continue with normal processing. While we are waiting for the master timeout we handle manual failover requests.
* Introduce timeout parameter to restart.
When restart timeout is set master becomes eligible for failover after that timeout expires regardless of master_start_time. Immediate restart calls will wait for this timeout to pass, even when node is a standby.
Previously replicas were always watching for leader key (even if the
postgres was not in the running there). It was not a big issue, but it
was not possible to interrupt such watch in cases if the postgres
started up or stopped successfully. Also it was delaying update_member
call and we had kind of stale information in DCS up to `loop_wait`
seconds. This commit changes such behavior. If the async_executor is
busy by starting/stopping or restarting postgres we will not watch for
leader key but waiting for event from async_executor up to `loop_wait`
seconds. Async executor will fire such event only in case if the
function it was calling returned something what could be evaluated to
boolean True.
Such functionality is really needed to change the way how we are making
decision about necessity of pg_rewind. It will require to have a local
postgres running and for us it is really important to get such
notification as soon as possible.
