It is possible to change a lot of parameters in runtime (including `restapi.listen`) by updating Patroni config file and sending SIGHUP to Patroni process.
If something was misconfigured it was throwing a weird exception and breaking `restapi` thread.
This PR improves friendliness of error message and avoids breaking of `restapi`.
* Take and apply some parameters from controldata when starting as replica
https://www.postgresql.org/docs/10/static/hot-standby.html#HOT-STANDBY-ADMIN
There is set of parameters which value on the replica must be not smaller than on the primary, otherwise replica will refuse to start:
* max_connections
* max_prepared_transactions
* max_locks_per_transaction
* max_worker_processes
It might happen that values of these parameters in the global configuration are not set high enough, what makes impossible to start a replica without human intervention. Usually it happens when we bootstrap a new cluster from the basebackup.
As a solution to this problem we will take values of above parameters from the pg_controldata output and in case if the values in the global configuration are not high enough, apply values taken from pg_controldata and set `pending_restart` flag.
Do not exit when the cluster system ID is empty or the one that doesn't pass the validation check. In that case, the cluster most likely needs a reinit; mention it in the result message.
Avoid terminating Patroni, as otherwise reinit cannot happen.
We already have a lot of logic in place to prevent failover in such case and restore all keys, but an accidental removal of `/config` key was effectively switching off pause mode for 1 cycle of HA loop.
Upon start postmaster process performs various safety checks if there is a postmaster.pid file in the data directory. Although Patroni already detected that the running process corresponding to the postmaster.pid is not a postmaster, the new postmaster might fail to start, because it thinks that postmaster.pid is already locked.
Important!!! Unlink of postmaster.pid isn't an option in this case, because it has a lot of nasty race conditions.
Luckily there is a workaround to this problem, we can pass the pid from postmaster.pid in the `PG_GRANDPARENT_PID` environment variable and postmaster will ignore it.
More likely to hit such problem if you run Patroni and postgres in the docker container.
It didn't affect directly neither failover nor switchover, but in some rare cases it was reporting it as a success too early, when the former leader released the lock: `Failed over to "None" instead of "desired-node"`
In addition to that this commit improves logs and status messages by differentiating between failover and switchover.
Patroni can attach itself to an already running PostgreSQL instance. If that is the first instance "seen" in the given cluster, Patroni for that instance will create the initialize key, grab the leader key and, if the instance is running a replica, promote.
Because of this behavior, when a cluster with a master and one or more replicas gets Patroni for each node, it is imperative to start running Patroni on the master node before getting to the replicas.
This commit changes such weird behavior and will abort Patroni start if there is no initialize key in DCS and postgres is running as a replica.
Closes https://github.com/zalando/patroni/issues/655
Output exception trace to the logs when http status code == 403, something is wrong with permissions.
When http status code == 409 -- such error could be ignored, because object probably was created or updated by another process.
For all other http status codes it will also produce stack traces.
I hope it will help to debug issues similar to the https://github.com/zalando/patroni/issues/606
It is very easy to get current timeline on the master by executing
```sql
SELECT ('x' || SUBSTR(pg_walfile_name(pg_current_wal_lsn()), 1, 8))::bit(32)::int
```
Unfortunately the same method doesn't work when postgres is_in_recovery. Therefore we will use replication connection for that on the replicas. In order to avoid opening and closing replication connection on every HA loop we will cache the result if its value matches with the timeline of the master.
Also this PR introduces a new key in DCS: `/history`. It will contain a json serialized object with timeline history in a format similar to the usual history files. The differences are:
* Second column is the absolute wal position in bytes, instead of LSN
* Optionally there might be a fourth column - timestamp, (mtime of history file)
Every iteration of HA loop Patroni needs to call pg_is_in_recovery() and calcualte absolute wal_position. It was doing two separate SELECT statements for that. In case of master it was doing even three queries (wal_position two times).
We will issue one SELECT for every HA loop and cache the results.
* 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`
This list will be used for initial discovery of etcd cluster members.
If for some reason during work this list of hosts has been exhausted (during work), Patroni will return to initial list.
In addition to that improve ipv6 compatibility by using a special function for splitting host and port.
Fixes https://github.com/zalando/patroni/issues/523
* Use ConfigMaps or Endpoins for leader elections and to keep cluster state
* Label pods with a postgres role
* change behavior of pip install. From now on it will not install all dependencies, you have to specify explicitly DCS you want to use Patroni with: `pip install patroni[etcd,zookeeper,kubernetes]`
* 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.
Introduces a PostmasterProcess object that identifies a running process via pid and start time.
When pid file is parsed and the correct process identified this object is passed around.
When the process goes away we try to find a new one in case somebody restarted postgres behind our back.
After a crash that doesn't clean up postmaster.pid there could be a new process with the same pid resulting in a false positive for is_running(), which will lead to all kinds of bad behavior.
Fixes#548
It could happen that ttl provided in Patroni configuration is smaller
than minimum supported by Consul. In such case Consul agent fails to
create a new session and responds with 500 Internal Server Error and
http body contains something like: "Invalid Session TTL '3000000000',
must be between [10s=24h0m0s]". Without session Patroni is not able to
create member and leader keys in the Consul KV store and it means that
cluster becomes completely unhealthy.
As a workaround we will handle such exception, adjust ttl to the minimum
possible and retry session creation.
In addition to that make it possible to define custom log format via environment variable `PATRONI_LOGFORMAT`
When Patroni does calculation whether it should run pg_rewind or not, it relies on pg_controldata output or gets necessary information from replication connection.
On some cases (when for example postgres running as a master was killed), we can't use pg_controldata output immediately, but trying to start postgres. Such start could fail with the following errror:
```
LOG,00000,"ending log output to stderr",,"Future log output will go to log destination ""csvlog"".",,,,,,,""
LOG,00000,"database system was interrupted; last known up at 2017-09-16 22:35:22 UTC",,,,,,,,,""
LOG,00000,"restored log file ""00000006.history"" from archive",,,,,,,,,""
LOG,00000,"entering standby mode",,,,,,,,,"" 2017-09-18 08:00:39.433 UTC,,,57,,59bf7d26.39,4,,2017-09-18 08:00:38 UTC,,0,LOG,00000,"restored log file ""00000006.history"" from archive",,,,,,,,,""
FATAL,XX000,"requested timeline 6 is not a child of this server's history","Latest checkpoint is at 29/1A000178 on timeline 5, but in the history of the requested timeline, the server forked off from that timeline at 29/1A000140.",,,,,,,,""
LOG,00000,"startup process (PID 57) exited with exit code 1",,,,,,,,,""
LOG,00000,"aborting startup due to startup process failure",,,,,,,,,""
LOG,00000,"database system is shut down",,,,,,,,,""
```
In this case controldata will still have `Database cluster state: in production`
All further attempts to start postgres will fail. Such situation could be fixed only if we start not in recovery. For safety we will do it in a single user mode.
The second problems is: if postgres was running as master, but later we started it and stopped, than pg_controldata will report:
```
Database cluster state: shut down in recovery
Minimum recovery ending location: 0/0
Min recovery ending loc's timeline: 0
```
And this info can't be used for calculations. In this case we should use
`Latest checkpoint location` and `Latest checkpoint's TimeLineID`
A misunderstanding of the ioctl() call interface. If mutable=False then fcntl.ioctl() actually returns the arg buffer back.
This accidentally worked on Python2 because int and str comparison did not return an error.
Error reporting is actually done by raising IOError on Python2 and OSError on Python3.
* Properly handle errors in set_timeout(), have them result in only a warning if watchdog support is not required.
* Improve watchdog device driver name display on Python3
* Eliminate race condition in watchdog feature tests.
The pinged/closed states were not getting reset properly if the checks ran too quickly.
Add explicit reset points in feature test so the check is unambiguous.
in addition to that implement additional checks around manual failover and recover when synchronous_mode is enabled
* Comparison must be case insensitive
* Do not send keepalives if watchdog is not active
* Avoid activating watchdog in a pause mode
* Set correct postgres state in pause mode
* Don't try to run queries from API if postgres is stopped
