[ANN] alertmanager v0.17.0 released

[Stuart Nelson]

Hey folks,

A new release for alertmanager, v0.17.0, has just been released.

This release includes changes to amtool which are not fully backwards
compatible with the previous amtool version (#1798) related to backup and
import of silences. If a backup of silences is created using a previous
version of amtool (v0.16.1 or earlier), it is possible that not all silences
can be correctly imported using a later version of amtool.

Additionally, the groups endpoint that was dropped from api v1 has been added
to api v2. The default for viewing alerts in the UI now consumes from this
endpoint and displays alerts grouped according to the groups defined in the
running configuration. Custom grouping is still supported.

This release has added two new flags that may need to be tweaked. For people
running with a lot of concurrent requests, consider increasing the value of
`--web.get-concurrency`. An increase in 503 errors indicates that the request
rate is exceeding the number of currently available workers. The other new
flag, --web.timeout, limits the time a request is allowed to run. The default
behavior is to not use a timeout.

Full changes are available here.

As always, please open an issue following the provided issue template for bugs in the release.

Stuart