Add ability to set Global tags using code and environment variables

README.md

@@ -12,11 +12,14 @@ Requires:
 ### Configuration
 Configuration values can be set either from environmental variables or code:
 
-`SIGNALFX_SERVICE_NAME` / [WithServiceName](https://godoc.org/github.com/signalfx/signalfx-go-tracing/tracing/#WithServiceName) Name identifying the service as a whole (defaults to `SignalFx-Tracing`)
-
-`SIGNALFX_ENDPOINT_URL` / [WithEndpointURL](https://godoc.org/github.com/signalfx/signalfx-go-tracing/tracing/#WithEndpointURL) URL to send traces to (defaults to `http://localhost:9080/v1/trace`)
-
-`SIGNALFX_ACCESS_TOKEN` / [WithAccessToken](https://godoc.org/github.com/signalfx/signalfx-go-tracing/tracing/#WithAccessToken) (no default)
+| Code | Environment Variable | Default Value | Notes |
+| ---  | ---                  | ---           | ---   |
+| [WithServiceName](https://godoc.org/github.com/signalfx/signalfx-go-tracing/tracing/#WithServiceName) | `SIGNALFX_SERVICE_NAME` | `SignalFx-Tracing` | The name of the service. |
+| [WithEndpointURL](https://godoc.org/github.com/signalfx/signalfx-go-tracing/tracing/#WithEndpointURL) | `SIGNALFX_ENDPOINT_URL` | `http://localhost:9080/v1/trace` | The URL to send traces to.  |
+| [WithAccessToken](https://godoc.org/github.com/signalfx/signalfx-go-tracing/tracing/#WithAccessToken) | `SIGNALFX_ACCESS_TOKEN` | none | |
+| [WithGlobalTag](https://godoc.org/github.com/signalfx/signalfx-go-tracing/tracing/#WithGlobalTag) | `SIGNALFX_SPAN_TAGS` | none | Comma-separated list of tags included in every reported span. For example, "key1:val1,key2:val2". Note: The current transport format is Zipkin which only supports string values for tags.|
+
+Note: The current transport format is Zipkin which only supports string values for tags.
 
 ### Getting Started
 When your application starts enable tracing globally with

tracing/opentracing_test.go

@@ -8,6 +8,7 @@ import (
 	"github.com/signalfx/signalfx-go-tracing/zipkinserver"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"os"
 	"testing"
 )
 
@@ -79,13 +80,73 @@ func TestOpenTracingParentSpan(t *testing.T) {
 }
 
 func TestEmptyContext(t *testing.T) {
+	assert := assert.New(t)
 	zipkin := zipkinserver.Start()
 	defer zipkin.Stop()
 
 	Start(WithEndpointURL(zipkin.URL()))
 
-	span, _ := opentracing.StartSpanFromContext(context.Background(), "session")
+	sessionName := "session"
+	span, _ := opentracing.StartSpanFromContext(context.Background(), sessionName)
+	span.Finish()
+
+	tracer.ForceFlush()
+	spans := zipkin.WaitForSpans(t, 1)
+	assert.Equal(sessionName, *spans[0].Name)
+}
+
+func TestWithGlobalTags(t *testing.T) {
+	require := require.New(t)
+
+	zipkin := zipkinserver.Start()
+	defer zipkin.Stop()
+
+	Start(WithEndpointURL(zipkin.URL()),
+		WithGlobalTag("abc-test", "1234"),
+		WithGlobalTag("test", "value"))
+
+	span := tracer.StartSpan("test")
+	span.Finish()
+
+	tracer.ForceFlush()
+	spans := zipkin.WaitForSpans(t, 1)
+
+	tags := spans[0].Tags
+	require.Equal(2, len(tags))
+	require.Equal("value",tags["test"], )
+	require.Equal("1234", tags["abc-test"])
+}
+
+func TestEnvironmentVariables(t *testing.T) {
+	assert := assert.New(t)
+	require := require.New(t)
+
+	// There will be no "  " key with value "silentjay" as Zipkin states empty keys are not valid.
+	err := os.Setenv(signalfxSpanTags, "a:b, c :d  , bob:,  : silentjay")
+	require.Nil(err)
+	defer os.Unsetenv(signalfxSpanTags)
+
+	zipkin := zipkinserver.Start()
+	defer zipkin.Stop()
+
+	Start(WithServiceName("MyService"),
+		WithEndpointURL(zipkin.URL()),
+		WithGlobalTag("abc-test", "1234"),
+		WithGlobalTag("test", "value"))
+
+	span := tracer.StartSpan("test")
 	span.Finish()
+
 	tracer.ForceFlush()
-	zipkin.WaitForSpans(t, 1)
+	spans := zipkin.WaitForSpans(t, 1)
+
+	assert.Equal("MyService", *spans[0].LocalEndpoint.ServiceName)
+
+	tags := spans[0].Tags
+	require.Equal(5, len(tags))
+	assert.Equal("value",tags["test"])
+	assert.Equal("1234", tags["abc-test"])
+	assert.Equal("b", tags["a"])
+	assert.Equal("d", tags["c"])
+	assert.Equal("", tags["bob"])
 }

tracing/tracing.go

@@ -5,12 +5,14 @@ import (
 	"github.com/signalfx/signalfx-go-tracing/ddtrace/opentracer"
 	"github.com/signalfx/signalfx-go-tracing/ddtrace/tracer"
 	"os"
+	"strings"
 )
 
 const (
 	signalfxServiceName = "SIGNALFX_SERVICE_NAME"
 	signalfxEndpointURL = "SIGNALFX_ENDPOINT_URL"
 	signalfxAccessToken = "SIGNALFX_ACCESS_TOKEN"
+	signalfxSpanTags    = "SIGNALFX_SPAN_TAGS"
 )
 
 var defaults = map[string]string{
@@ -23,6 +25,10 @@ type config struct {
 	serviceName string
 	accessToken string
 	url         string
+	// Because there can be multiple global tags added via environment variable
+	// or calls to WithGlobalTag, store them in the required StartOption format to
+	// call tracer.Start() in the variadic format.
+	globalTags []tracer.StartOption
 }
 
 // StartOption is a function that configures an option for Start
@@ -33,9 +39,41 @@ func defaultConfig() *config {
 		serviceName: envOrDefault(signalfxServiceName),
 		accessToken: envOrDefault(signalfxAccessToken),
 		url:         envOrDefault(signalfxEndpointURL),
+		globalTags:  envGlobalTags(),
 	}
 }
 
+// envGlobalTags extract global tags from the environment variable and parses the value in the expected format
+// key1:value1,
+func envGlobalTags() []tracer.StartOption {
+	var globalTags []tracer.StartOption
+	var val string
+
+	if val = os.Getenv(signalfxSpanTags); val == "" {
+		return globalTags
+	}
+
+	tags := strings.Split(val, ",")
+	for _, tag := range tags {
+		// TODO: Currently this assumes "<stringb>" where "<stringa>:<stringb>" has no ":" in the
+		// string. The TODO is to fix this logic to allow for "<stringb> to have colons, ":', in it.
+		pair :=strings.Split(tag, ":")
+		if len(pair) == 2 {
+			key := strings.TrimSpace(pair[0])
+			value := strings.TrimSpace(pair[1])
+			// Empty keys aren't valid in Zipkin.
+			// https://github.com/openzipkin/zipkin-api/blob/d3324ac79d1aa8f5c6f0ea4febb299402e50480f/zipkin-jsonv2.proto#L50-L51
+			if key == "" {
+				continue
+			}
+			globalTag := tracer.WithGlobalTag(key, value)
+			globalTags = append(globalTags, globalTag)
+		}
+	}
+
+	return globalTags
+}
+
 // envOrDefault gets the given environment variable if set otherwise a default value.
 func envOrDefault(envVar string) string {
 	if val := os.Getenv(envVar); val != "" {
@@ -65,16 +103,30 @@ func WithEndpointURL(url string) StartOption {
 	}
 }
 
+// WithGlobalTag sets a tag with the given key/value on all spans created by the
+// tracer. This option may be used multiple times.
+// Note: Since the underlying transport is Zipkin, only values with strings
+// are accepted.
+func WithGlobalTag(k string, v string) StartOption {
+	return func(c *config) {
+		globalTag := tracer.WithGlobalTag(k, v)
+		c.globalTags = append(c.globalTags, globalTag)
+	}
+}
+
 // Start tracing globally
 func Start(opts ...StartOption) {
 	c := defaultConfig()
 	for _, fn := range opts {
 		fn(c)
 	}
 
+	startOptions := append(c.globalTags, tracer.WithServiceName(c.serviceName))
+	startOptions = append(startOptions, tracer.WithZipkin(c.serviceName, c.url, c.accessToken))
 	tracer.Start(
-		tracer.WithServiceName(c.serviceName),
-		tracer.WithZipkin(c.serviceName, c.url, c.accessToken))
+		startOptions...
+	)
+
 	opentracing.SetGlobalTracer(opentracer.New())
 }