Add support for Datadog APM tracing

Addresses arachnys#188

weaver/Gopkg.toml

@@ -57,6 +57,14 @@
   name = "gopkg.in/alexcesaro/statsd.v2"
   version = "2.0.0"
 
+[[constraint]]
+  name = "github.com/stretchr/testify"
+  version = "1.3.0"
+
 [prune]
   go-tests = true
   unused-packages = true
+
+[[constraint]]
+  name = "gopkg.in/DataDog/dd-trace-go.v1"
+  version = "1.9.0"

weaver/README.md

@@ -26,6 +26,7 @@ Although it was predominantly designed for generating a PDF from a HTML using [`
 - Strong service visibility for quality control:
     - Metrics collection ([statsd])
     - Error logging ([Sentry][sentry])
+    - APM ([Datadog APM][ddapm])
 - Dockerized:
     - Easy to set up, distribute, and deploy
     - Runs in headless mode (the display server is handled for you)
@@ -52,3 +53,4 @@ See [`docs/building.md`](docs/building.md).
 [cloudconvert]: https://cloudconvert.com/
 [statsd]: https://github.com/etsy/statsd
 [sentry]: https://getsentry.com/
+[ddapm]: https://www.datadoghq.com/apm/

weaver/conf/sample.env

@@ -17,3 +17,7 @@ WEAVER_CONVERSION_FALLBACK=false
 # STATSD_ADDRESS=
 # STATSD_PREFIX=
 # SENTRY_DSN=
+
+# Datadog APM tracing
+# DATADOG_AGENT_ADDRESS=
+# DATADOG_APM_SERVICE_NAME=

weaver/config.go

@@ -67,21 +67,28 @@ type Config struct {
 	// The data source name (DSN) for a Sentry server (used for logging errors).
 	// Defaults to none.
 	SentryDSN string
+	// Hostname (and port) for reporting Datadog APM traces.
+	// Defaults to none (no trace reporting).
+	DatadogAgentAddress string
+	// Service name to report to Datadog APM
+	// Defaults to "weaver"
+	DatadogAPMServiceName string
 }
 
 // NewEnvConfig initialises configuration variables from the environment.
 func NewEnvConfig() Config {
 	// Set defaults
 	cloudconvert := CloudConvert{APIUrl: "https://api.cloudconvert.com"}
 	conf := Config{
-		CloudConvert:       cloudconvert,
-		HTTPAddr:           ":8080",
-		AuthKey:            "arachnys-weaver",
-		AthenaCMD:          "athenapdf -S",
-		MaxWorkers:         10,
-		MaxConversionQueue: 50,
-		WorkerTimeout:      90,
-		ConversionFallback: false,
+		CloudConvert:          cloudconvert,
+		HTTPAddr:              ":8080",
+		AuthKey:               "arachnys-weaver",
+		AthenaCMD:             "athenapdf -S",
+		MaxWorkers:            10,
+		MaxConversionQueue:    50,
+		WorkerTimeout:         90,
+		ConversionFallback:    false,
+		DatadogAPMServiceName: "weaver",
 	}
 
 	if httpAddr := os.Getenv("WEAVER_HTTP_ADDR"); httpAddr != "" {
@@ -145,5 +152,13 @@ func NewEnvConfig() Config {
 		conf.SentryDSN = sentryDSN
 	}
 
+	if datadogAgentAddress := os.Getenv("DATADOG_AGENT_ADDRESS"); datadogAgentAddress != "" {
+		conf.DatadogAgentAddress = datadogAgentAddress
+	}
+
+	if datadogAPMServiceName := os.Getenv("DATADOG_APM_SERVICE_NAME"); datadogAPMServiceName != "" {
+		conf.DatadogAPMServiceName = datadogAPMServiceName
+	}
+
 	return conf
 }

weaver/config_test.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"github.com/stretchr/testify/assert"
+	"os"
+	"testing"
+)
+
+func TestNewEnvConfig(t *testing.T) {
+	t.Run("Datadog Agent Address", func(t *testing.T) {
+		c := NewEnvConfig()
+		assert.Equal(t, "", c.DatadogAgentAddress)
+
+		expectValue := "123qweasdzxc:12312"
+		err := os.Setenv("DATADOG_AGENT_ADDRESS", expectValue)
+		assert.Nil(t, err)
+
+		c = NewEnvConfig()
+		assert.Equal(t, expectValue, c.DatadogAgentAddress)
+	})
+
+	t.Run("Datadog APM Service Name", func(t *testing.T) {
+		c := NewEnvConfig()
+		assert.Equal(t, "weaver", c.DatadogAPMServiceName)
+
+		expectValue := "12o38y27345987234695thekgjr"
+		err := os.Setenv("DATADOG_APM_SERVICE_NAME", expectValue)
+		assert.Nil(t, err)
+
+		c = NewEnvConfig()
+		assert.Equal(t, expectValue, c.DatadogAPMServiceName)
+	})
+}