Override Promtail User-Agent header (#270)

* override Loki User-Agent header

Fixes #188

* update CHANGELOG

* revert hacky workaround, no longer needed now that fix in loki is merged

* use prometheus version for setting user-agent header

This avoids the same problem that Loki originally had and allows
downstream importers that use prometheus/common/version to import
the loki package without it overwriting their build info.

CHANGELOG.md

@@ -33,6 +33,9 @@ this platform. FreeBSD builds will return in a future release.
 - [BUGFIX] Fix issue where the Tempo example manifest could not be applied
   because the port names were too long. (@rfratto)
 
+- [CHANGE] The User-Agent header sent for logs will now be
+  `GrafanaCloudAgent/<version>` (@rfratto)
+
 # v0.8.0 (2020-11-06)
 
 NOTE: FreeBSD builds will not be included for this release. There is a bug in an

pkg/build/build.go

@@ -1,13 +1,6 @@
 package build
 
-import (
-	// We do an empty import of Loki's build package to force it ahead of us on
-	// the dependency graph. This makes sure that our init function runs after it
-	// and retains the build info we set at compile time.
-	_ "github.com/grafana/loki/pkg/build"
-
-	"github.com/prometheus/common/version"
-)
+import "github.com/prometheus/common/version"
 
 // Version information passed to Prometheus version package.
 // Package path as used by linker changes based on vendoring being used or not,

pkg/loki/loki.go

@@ -3,6 +3,7 @@ package loki
 
 import (
 	"flag"
+	"fmt"
 
 	"github.com/go-kit/kit/log"
 	"github.com/go-kit/kit/log/level"
@@ -13,8 +14,13 @@ import (
 	"github.com/grafana/loki/pkg/promtail/scrapeconfig"
 	"github.com/grafana/loki/pkg/promtail/server"
 	"github.com/grafana/loki/pkg/promtail/targets/file"
+	"github.com/prometheus/common/version"
 )
 
+func init() {
+	client.UserAgent = fmt.Sprintf("GrafanaCloudAgent/%s", version.Version)
+}
+
 // Config controls the configuration of the Loki log scraper.
 type Config struct {
 	// Whether the Loki subsystem should be enabled.