Building with librdkafka 1.6+ doesn't require librdkafka library any more

[johnseekins]

As proof:

$ git log | head -n 20
commit 79930f5b3829279f282a9f5866a7e412cbcf549a
Merge: dc1cfdd d1cbd70
Author: John Seekins <jseekins@datto.com>
Date:   Mon May 3 10:07:32 2021 -0600

    remove build of librdkafka (comes with package now):

commit d1cbd70c213248b3597adbdd4d2ddbf6173b47bd
Author: Gallardot <tttick@163.com>
Date:   Sun Apr 11 01:54:21 2021 +0800

    add match rule (#64)

commit 732b9f69e14169c86daefdcc1cba41e8615be9fb
Author: Javier Provecho (Telefonica) <54402687+jpfe-tid@users.noreply.github.com>
Date:   Mon Mar 15 08:08:25 2021 +0100

    feat: update dockerfile base and deps (#63)

commit 1c0fdd9b1702e8726202f56af20df245ba7911f7
jseekins@quietthinkpad:~/github/prometheus-kafka-adapter$ docker run --rm -v $(pwd):/app:z -w /app golang:1.16.1-buster go build -o prometheus-kafka-adapter .
go: downloading github.com/gogo/protobuf v1.3.1
go: downloading github.com/gin-gonic/contrib v0.0.0-20191209060500-d6e26eeaa607
go: downloading github.com/golang/snappy v0.0.1
go: downloading github.com/gin-gonic/gin v1.6.3
go: downloading github.com/confluentinc/confluent-kafka-go v1.6.1
go: downloading github.com/linkedin/goavro v2.1.0+incompatible
go: downloading github.com/prometheus/client_golang v0.8.0
go: downloading github.com/prometheus/client_model v0.2.0
go: downloading github.com/prometheus/common v0.0.0-20180801064454-c7de2306084e
go: downloading github.com/prometheus/prometheus v2.4.2+incompatible
go: downloading github.com/sirupsen/logrus v1.6.0
go: downloading gopkg.in/yaml.v2 v2.2.8
go: downloading github.com/golang/protobuf v1.3.3
go: downloading github.com/beorn7/perks v1.0.1
go: downloading github.com/prometheus/procfs v0.1.3
go: downloading github.com/gin-contrib/sse v0.1.0
go: downloading github.com/mattn/go-isatty v0.0.12
go: downloading gopkg.in/alecthomas/kingpin.v2 v2.2.6
go: downloading github.com/matttproud/golang_protobuf_extensions v1.0.1
go: downloading golang.org/x/sys v0.0.0-20200116001909-b77594299b42
go: downloading github.com/go-playground/validator/v10 v10.2.0
go: downloading github.com/ugorji/go v1.1.7
go: downloading github.com/grpc-ecosystem/grpc-gateway v1.5.0
go: downloading golang.org/x/net v0.0.0-20180826012351-8a410e7b638d
go: downloading google.golang.org/genproto v0.0.0-20180928223349-c7e5094acea1
go: downloading google.golang.org/grpc v1.15.0
go: downloading github.com/ugorji/go/codec v1.1.7
go: downloading github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751
go: downloading github.com/alecthomas/units v0.0.0-20190924025748-f65c72e2690d
go: downloading github.com/go-playground/universal-translator v0.17.0
go: downloading github.com/leodido/go-urn v1.2.0
go: downloading golang.org/x/text v0.3.2
go: downloading github.com/go-playground/locales v0.13.0
jseekins@quietthinkpad:~/github/prometheus-kafka-adapter$ ./prometheus-kafka-adapter 
{"level":"warning","msg":"invalid serialization format, using json","serialization-format-value":"","time":"2021-05-03T10:08:55-06:00"}
INFO[0000] creating kafka producer                       source="main.go:29"
[GIN-debug] [WARNING] Running in "debug" mode. Switch to "release" mode in production.
 - using env:	export GIN_MODE=release
 - using code:	gin.SetMode(gin.ReleaseMode)

[GIN-debug] GET    /metrics                  --> github.com/gin-gonic/gin.WrapH.func1 (3 handlers)
[GIN-debug] POST   /receive                  --> main.receiveHandler.func1 (3 handlers)
[GIN-debug] Environment variable PORT is undefined. Using port :8080 by default
[GIN-debug] Listening and serving HTTP on :8080
%3|1620058136.932|FAIL|rdkafka#producer-1| [thrd:kafka:9092/bootstrap]: kafka:9092/bootstrap: Failed to resolve 'kafka:9092': Name or service not known (after 1497ms in state CONNECT)
^C

Essentially, we can simplify the build down to nearly one command. Which is kinda nice.

[jpfe-tid]

The proof of work that you posted is not equivalent to the build process within the Dockerfile. The binary produced works because you're (presumably) using a libc based distribution.

prometheus-kafka-adapter is built statically from a libc distribution, debian buster, to allow a slimmer final image, for example based on alpine, which uses musl-libc.

The reason of building in debian buster is related to #62 and #63, where there were issues when building prometheus-kafka-adapter in the same distribution as the final image, due to librdkafka dependency.

Updating golang version from 1.16.1 to 1.16.3 and removing apt install build-essential, looks good to me.

Please revert ldflags deletion from Dockerfile, as in this state, the image doesn't work.

/bin/sh: /prometheus-kafka-adapter: not found

[jpfe-tid]

Thanks for your PR @johnseekins ! 🚀