Added Tag Configuration Support Lightstep Tracing

CHANGELOG.md

@@ -16,7 +16,9 @@ We use _breaking :warning:_ to mark changes that are not backward compatible (re
 
 - [#4107](https://github.com/thanos-io/thanos/pull/4107) Store: `LabelNames` and `LabelValues` now support label matchers.
 - [#4171](https://github.com/thanos-io/thanos/pull/4171) Docker: Busybox image updated to latest (1.33.1)
+- [#4175](https://github.com/thanos-io/thanos/pull/4175) Added Tag Configuration Support Lightstep Tracing
 - [#4176](https://github.com/thanos-io/thanos/pull/4176) Query API: Adds optional `Stats param` to return stats for query APIs
+
 ### Fixed
 -
 ### Changed

docs/tracing.md

@@ -119,4 +119,5 @@ config:
     port: 0
     plaintext: false
     custom_ca_cert_file: ""
+  tags: ""
 ```

pkg/tracing/lightstep/lightstep.go

@@ -6,6 +6,8 @@ package lightstep
 import (
 	"context"
 	"io"
+	"os"
+	"strings"
 
 	"github.com/lightstep/lightstep-tracer-go"
 	"github.com/opentracing/opentracing-go"
@@ -21,6 +23,9 @@ type Config struct {
 	// Collector is the host, port, and plaintext option to use
 	// for the collector.
 	Collector lightstep.Endpoint `yaml:"collector"`
+
+	// Tags is a string comma-delimited of key value pairs that holds metadata that will be sent to lightstep
+	Tags string `yaml:"tags"`
 }
 
 // Tracer wraps the Lightstep tracer and the context.
@@ -43,9 +48,15 @@ func NewTracer(ctx context.Context, yamlConfig []byte) (opentracing.Tracer, io.C
 		return nil, nil, err
 	}
 
+	var tags opentracing.Tags
+	if config.Tags != "" {
+		tags = parseTags(config.Tags)
+	}
+
 	options := lightstep.Options{
 		AccessToken: config.AccessToken,
 		Collector:   config.Collector,
+		Tags:        tags,
 	}
 	lighstepTracer, err := lightstep.CreateTracer(options)
 	if err != nil {
@@ -58,3 +69,30 @@ func NewTracer(ctx context.Context, yamlConfig []byte) (opentracing.Tracer, io.C
 	}
 	return t, t, nil
 }
+
+// parseTags parses the given string into a map of strings to empty interface.
+// Spec for this value:
+// - comma separated list of key=value
+// - value can be specified using the notation ${envVar:defaultValue}, where `envVar`
+// is an environment variable and `defaultValue` is the value to use in case the env var is not set.
+func parseTags(sTags string) opentracing.Tags {
+	pairs := strings.Split(sTags, ",")
+	tags := make(opentracing.Tags)
+	for _, p := range pairs {
+		kv := strings.SplitN(p, "=", 2)
+		k, v := strings.TrimSpace(kv[0]), strings.TrimSpace(kv[1])
+
+		if strings.HasPrefix(v, "${") && strings.HasSuffix(v, "}") {
+			ed := strings.SplitN(v[2:len(v)-1], ":", 2)
+			e, d := ed[0], ed[1]
+			v = os.Getenv(e)
+			if v == "" && d != "" {
+				v = d
+			}
+		}
+
+		tags[k] = v
+	}
+
+	return tags
+}

pkg/tracing/lightstep/lightstep_test.go

@@ -0,0 +1,60 @@
+// Copyright (c) The Thanos Authors.
+// Licensed under the Apache License 2.0.
+
+package lightstep
+
+import (
+	"os"
+	"testing"
+
+	"github.com/thanos-io/thanos/pkg/testutil"
+
+	"github.com/opentracing/opentracing-go"
+)
+
+func TestParseTags(t *testing.T) {
+	type testData struct {
+		input          string
+		description    string
+		expectedOutput opentracing.Tags
+	}
+
+	testingData := []testData{
+		{
+			description:    `A very simple case, key "foo" and value "bar"`,
+			input:          "foo=bar",
+			expectedOutput: opentracing.Tags{"foo": "bar"},
+		},
+		{
+			description:    `A simple case multiple keys, keys ["foo", "bar"] and values ["foo", "bar"]`,
+			input:          "foo=foo,bar=bar",
+			expectedOutput: opentracing.Tags{"foo": "foo", "bar": "bar"},
+		},
+		{
+			description:    `A case with empty environment variable, key "foo" and value ""`,
+			input:          "foo=${TEST:}",
+			expectedOutput: opentracing.Tags{"foo": ""},
+		},
+		{
+			description:    `A case with empty environment variable, key "foo" and value ""`,
+			input:          "foo=${TEST:}",
+			expectedOutput: opentracing.Tags{"foo": ""},
+		},
+		{
+			description:    `A case with default environment variable, key "foo" and value "default"`,
+			input:          "foo=${TEST:default}",
+			expectedOutput: opentracing.Tags{"foo": "default"},
+		},
+		{
+			description:    `A case with real environment variable, key "foo" and value "env-bar"`,
+			input:          "foo=${_TEST_PARSE_TAGS:default}",
+			expectedOutput: opentracing.Tags{"foo": "env-bar"},
+		},
+	}
+
+	os.Setenv("_TEST_PARSE_TAGS", "env-bar")
+	for _, test := range testingData {
+		t.Logf("testing %s\n", test.description)
+		testutil.Equals(t, test.expectedOutput, parseTags(test.input))
+	}
+}