This is #2819 but rebased on latest `main`. This PR is against main too
as opposed to the `moderncsqlite` branch.
The main change here is simply:
```go
// add query parameters to the dsn
if strings.Contains(dsn, "?") {
dsn += "&"
} else {
dsn += "?"
}
// wait some time before erroring if the db is locked
// https://gitlab.com/cznic/sqlite/-/issues/106#note_1058094993
dsn += "_pragma=busy_timeout%3d10000"
```
### Pull Request Checklist
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https://matrix-org.github.io/dendrite/development/contributing before
submitting your pull request -->
* [x] I have added tests for PR _or_ I have justified why this PR
doesn't need tests.
* [x] Pull request includes a [sign off below using a legally
identifiable
name](https://matrix-org.github.io/dendrite/development/contributing#sign-off)
_or_ I have already signed off privately
Signed off privately.
Co-authored-by: Neil Alexander <neilalexander@users.noreply.github.com>
This PR queries PostgreSQL for the `max_connections` and
`superuser_reserved_connections` settings and then ensures that
Dendrite's `max_open_conns` doesn't exceed the allowed value.
This is a really common source of configuration problems and can either
result in blocking queries or deadlocks, so it seems reasonable that we
complain as loudly as possible when it happens.