The controller implementation is primarily used by influxdb so it
shouldn't be part of the flux repository. This copies the code from flux
to influxdb so it can be removed from the next flux release.
I did this with a dumb editor macro, so some comments changed too.
Also rename root package from platform to influxdb.
In interest of minimizing risk, anyone importing the root package has
now aliased it to "platform" so that no changes beyond imports were
necessary in those files.
Lastly, replace the old platform module to local path /dev/null so that
nobody can accidentally reintroduce a platform dependency while
migrating platform code to influxdb.
The flux query controller was updated to include a Shutdown method a
while ago. Explicitly handle query controller creation and shutdown
where applicable.
In influxd, this ensures that outstanding queries are handled before the
process dies. In tests, this ensures that query controller goroutines
aren't leaked, which drastically simplifies reading full stack traces.
This change also registers query controller metrics with the prometheus
registry in influxd.
This pulls in the code that allows doing reads with flux into the
platform repo, and removes extra.go.
The reusable portion is under storage/reads, where the concrete
implementation for one of the platform's engines is in
storage/readservice.
In order to make this more reusable, the cursors had to move into
their own package, decoupling it from all of the other code in the
tsdb package. tsdb/cursors is this new package, and type/function
aliases have been added to the tsdb package to point at it.
The models package already is very light on transitive dependencies
and so it was allowed to be depended on in a concrete way in the
cursors package.
Finally, the protobuf definitions for issuing GRPC reads has been
moved into its own package for two reasons:
1. It's a clean separation, and helps keep it that way.
2. Many/most consumers will not be using GRPC. We just
use the datatypes to express the API which helps making
a GRPC server easier.
It is left up to future refactorings (specifically ones that involve
GPRC) to determine if these types should remain, or if there is a
cleaner way.
There's still some dependencies on both github.com/influxdata/influxql
and github.com/influxdata/influxdb/logger that we can hopefully remove
in future refactorings.