We monitor the health of DB replicas, and on a fatal error,
take them out of the pool.
On a separate goroutine, we keep pinging the unhealthy replicas,
and on getting a good response back, we add them back to the pool.
https://mattermost.atlassian.net/browse/MM-50427
```release-note
Mattermost is now resilient against DB replica outages and will
dynamically choose a replica if it's alive.
Also added a config parameter ReplicaMonitorIntervalSeconds
whose default value is 5. This controls how frequently unhealthy
replicas will be monitored for liveness check.
```
Co-authored-by: Mattermost Build <build@mattermost.com>
This will be shown in the system console to let users know
which search backend is active.
Implemented via adding an extra param in the ping response.
https://mattermost.atlassian.net/browse/MM-49984
```release-note
The database section in the system console now has an additional
read-only section which shows the active search backend in use.
This can be helpful to confirm which is the currently active
search engine when there are multiple of them configured.
```
---------
Co-authored-by: Mattermost Build <build@mattermost.com>
Mockery started to throw errors like "Unexpected package creation during export data loading".
This was consistently reproducible locally and on upgrade, it has gone away.
```release-note
NONE
```
* MM-45956: Optimize FileInfo stats query
We Denormalize Post.ChannelId on FileInfo.ChannelId
```release-note
The file info stats query is now optimized by denormalizing the channelID column into the table itself. This will speed up the query to get the file count for a channel on clicking the RHS.
Migration times:
On a MySQL 8.0.31 DB with
1405 rows in FileInfo and 11M posts, it took around 0.3s
On a Postgres 12.14 DB with
1731 rows in FileInfo and 11M posts, it took around 0.27s
```
https://mattermost.atlassian.net/browse/MM-45956
