Bump prometheus dependency to v2.21.0

[pmalek-sumo]

Bump Prometeus dependency to v2.21.0.

In order to achieve this the following go get was performed:

go get github.com/prometheus/prometheus@e83ef207b6c2398919b69cd87d2693cfc2fb4127

The reason for this is that Prometheus doesn't follow Go module semver conventions (its module should have a /v2 suffix but there's no intention in doing this - prometheus/prometheus#7991 (comment)).

The remaining changes are coming from a change in PB files from github.com/prometheus/prometheus/prompb from 1 to 2 via PR

Motivation

Apart from being up to date the motivation it will allow other projects to use telegraf package's e.g. github.com/influxdata/telegraf/agent.

The use case where I hit this was when I was trying to import github.com/influxdata/telegraf/agent from within https://github.com/open-telemetry/opentelemetry-collector-contrib which gave me the following errors:

GO111MODULE=on CGO_ENABLED=0 go build -o ./bin/otelcontribcol_unstable_darwin_amd64 \
                -ldflags "-X github.com/open-telemetry/opentelemetry-collector-contrib/internal/version.GitHash=63b2f339 -X github.com/open-telemetry/opentelemetry-collector-contrib/internal/version.Version=v0.19.0 -X go.opentelemetry.io/collector/internal/version.BuildType=release" -tags enable_unstable ./cmd/otelcontribcol
go: finding module for package github.com/prometheus/prometheus/discovery/install
go: finding module for package github.com/Azure/azure-sdk-for-go/arm/compute
go: finding module for package github.com/Azure/azure-sdk-for-go/arm/network
../../../.gvm/pkgsets/go1.15.7/global/pkg/mod/github.com/prometheus/prometheus@v2.5.0+incompatible/discovery/azure/azure.go:24:2: module github.com/Azure/azure-sdk-for-go@latest found (v51.0.0+incompatible), but does not contain package github.com/Azure/azure-sdk-for-go/arm/compute
../../../.gvm/pkgsets/go1.15.7/global/pkg/mod/github.com/prometheus/prometheus@v2.5.0+incompatible/discovery/azure/azure.go:25:2: module github.com/Azure/azure-sdk-for-go@latest found (v51.0.0+incompatible), but does not contain package github.com/Azure/azure-sdk-for-go/arm/network
../../../.gvm/pkgsets/go1.15.7/global/pkg/mod/github.com/prometheus/prometheus@v2.5.0+incompatible/discovery/consul/consul.go:27:2: ambiguous import: found package github.com/hashicorp/consul/api in multiple modules:
        github.com/hashicorp/consul v1.2.1 (/Users/DUMMY/.gvm/pkgsets/go1.15.7/global/pkg/mod/github.com/hashicorp/consul@v1.2.1/api)
        github.com/hashicorp/consul/api v1.7.0 (/Users/DUMMY/.gvm/pkgsets/go1.15.7/global/pkg/mod/github.com/hashicorp/consul/api@v1.7.0)
../../../.gvm/pkgsets/go1.15.7/global/pkg/mod/go.opentelemetry.io/collector@v0.19.0/receiver/prometheusreceiver/factory.go:22:2: module github.com/prometheus/prometheus@latest found (v2.5.0+incompatible), but does not contain package github.com/prometheus/prometheus/discovery/install

Please note the v2.5.0+incompatible that is required as of now (which doesn't understand Go modules hence most of the problems listed above).

[telegraf-tiger]

🤝 ✅ CLA has been signed. Thank you!

[pmalek-sumo]

Ok so unfortunately this makes the tests to fail because of an assertion in google.golang.org/protobuf@v1.24.0

https://github.com/protocolbuffers/protobuf-go/blob/v1.24.0/internal/impl/legacy_message.go#L136

panic: mismatching message name: got k8s.io.kubernetes.pkg.watch.versioned.Event, want github.com/ericchiang.k8s.watch.versioned.Event

goroutine 1 [running]:
google.golang.org/protobuf/internal/impl.legacyLoadMessageDesc(0x11cec20, 0x1043b60, 0x10ae672, 0x2f, 0x0, 0xa2b100)
	/go/pkg/mod/google.golang.org/protobuf@v1.24.0/internal/impl/legacy_message.go:136 +0xa38
google.golang.org/protobuf/internal/impl.legacyLoadMessageInfo(0x11cec20, 0x1043b60, 0x10ae672, 0x2f, 0xc0001b1e60)
	/go/pkg/mod/google.golang.org/protobuf@v1.24.0/internal/impl/legacy_message.go:48 +0xf3
google.golang.org/protobuf/internal/impl.Export.LegacyMessageTypeOf(0x11bbf40, 0x0, 0x10ae672, 0x2f, 0xc000224410, 0xc0002ac000)
	/go/pkg/mod/google.golang.org/protobuf@v1.24.0/internal/impl/legacy_export.go:33 +0xd6
github.com/golang/protobuf/proto.RegisterType(0x11bbf40, 0x0, 0x10ae672, 0x2f)
	/go/pkg/mod/github.com/golang/protobuf@v1.4.2/proto/registry.go:186 +0x6a
github.com/ericchiang/k8s/watch/versioned.init.0()
	/go/pkg/mod/github.com/ericchiang/k8s@v1.2.0/watch/versioned/generated.pb.go:70 +0x59
FAIL	github.com/influxdata/telegraf/plugins/inputs/prometheus	0.037s

[sspaink]

@pmalek-sumo Thank you for this pr, I've updated the Kubernetes go client in this pr #8937 so the failure in the tests you were getting should be resolvable now.

[telegraf-tiger]

Looks like new artifacts were built from this PR. Get them here!

Artifact URLs

• aarch64.rpm

• armel.rpm

• armv6hl.rpm

• i386.rpm

• ppc64le.rpm

• s390x.rpm

• x86_64.rpm

• darwin_amd64.tar.gz

• freebsd_amd64.tar.gz

• freebsd_i386.tar.gz

• linux_amd64.tar.gz

• linux_arm64.tar.gz

• linux_armel.tar.gz

• linux_armhf.tar.gz

• linux_i386.tar.gz

• linux_mips.tar.gz

• linux_mipsel.tar.gz

• linux_ppc64le.tar.gz

• linux_s390x.tar.gz

• static_linux_amd64.tar.gz

• windows_amd64.zip

• windows_i386.zip

• amd64.deb

• arm64.deb

• armel.deb

• armhf.deb

• i386.deb

• mips.deb

• mipsel.deb

• ppc64el.deb

• s390x.deb

[pmalek-sumo]

Thanks @sspaink ! It seems the patch is now clean to apply.

[sspaink]

Looks good!