Add generic metric function

metrics.go

@@ -12,6 +12,7 @@ import (
 	"io"
 	"os"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/FollowTheProcess/metrics/unit"
@@ -65,6 +66,8 @@ type MetricDefinition struct {
 }
 
 // Logger is the mechanism to write EMF metrics.
+//
+// A Logger is safe to use concurrently across goroutines.
 type Logger struct {
 	// Where to write EMF metrics to.
 	stdout io.Writer
@@ -81,6 +84,9 @@ type Logger struct {
 
 	// The actual metrics.
 	metrics MetricDirective
+
+	// Synchronisation
+	mu sync.Mutex
 }
 
 // Option is a functional option to configure a Logger.
@@ -141,13 +147,25 @@ func New(opts ...Option) *Logger {
 }
 
 // Count records a count metric.
-func (l *Logger) Count(name string, count int, resolution StorageResolution) *Logger {
-	l.store(name, count, unit.Count, resolution)
+func (l *Logger) Count(name string, count int, res StorageResolution) *Logger {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	l.store(name, count, unit.Count, res)
+	return l
+}
+
+// Add records a generic user defined metric.
+func (l *Logger) Add(name string, value any, unit unit.Unit, res StorageResolution) *Logger {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	l.store(name, value, unit, res)
 	return l
 }
 
 // Dimension adds a metrics dimension.
 func (l *Logger) Dimension(key, value string) *Logger {
+	l.mu.Lock()
+	defer l.mu.Unlock()
 	l.metrics.Dimensions = append(l.metrics.Dimensions, Dimension{key})
 	l.values[key] = value
 	return l
@@ -181,12 +199,12 @@ func (l *Logger) Flush() error {
 }
 
 // store inserts a metric into the Logger, to be flushed later.
-func (l *Logger) store(name string, value any, unit unit.Unit, resolution StorageResolution) {
+func (l *Logger) store(name string, value any, unit unit.Unit, res StorageResolution) {
 	// Store the metric metadata
 	metric := MetricDefinition{
 		Name:       name,
 		Unit:       unit,
-		Resolution: resolution,
+		Resolution: res,
 	}
 	l.metrics.Metrics = append(l.metrics.Metrics, metric)
 

metrics_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 
 	"github.com/FollowTheProcess/metrics"
+	"github.com/FollowTheProcess/metrics/unit"
 	"github.com/FollowTheProcess/test"
 	"github.com/kinbiko/jsonassert"
 )
@@ -20,13 +21,26 @@ func TestMetricsLog(t *testing.T) {
 		logFn func(*metrics.Logger) // Function to apply to the logger for the test
 		want  string                // Name of file containing expected JSON
 	}{
+		{
+			name:  "no metrics means empty json",
+			logFn: func(logger *metrics.Logger) {},
+			want:  "empty.json",
+		},
 		{
 			name: "count",
 			logFn: func(logger *metrics.Logger) {
 				logger.Count("something", 5, metrics.StandardResolution)
 			},
 			want: "count.json",
 		},
+		{
+			name: "count with trace id",
+			env:  map[string]string{"_X_AMZN_TRACE_ID": "something_looks_like_id_with_Sampled=1"},
+			logFn: func(logger *metrics.Logger) {
+				logger.Count("something", 5, metrics.StandardResolution)
+			},
+			want: "traceid.json",
+		},
 		{
 			name: "count high resolution",
 			logFn: func(logger *metrics.Logger) {
@@ -41,6 +55,13 @@ func TestMetricsLog(t *testing.T) {
 			},
 			want: "dimensions.json",
 		},
+		{
+			name: "generic metric",
+			logFn: func(logger *metrics.Logger) {
+				logger.Add("Foo", 27, unit.Percent, metrics.StandardResolution)
+			},
+			want: "generic.json",
+		},
 	}
 
 	for _, tt := range tests {

testdata/generic.json

@@ -0,0 +1,31 @@
+{
+  "_aws": {
+    "Timestamp": "<<PRESENCE>>",
+    "CloudWatchMetrics": [
+      {
+        "Namespace": "aws-embedded-metrics",
+        "Dimensions": [
+          [
+            "ServiceName",
+            "ServiceType"
+          ]
+        ],
+        "Metrics": [
+          {
+            "Name": "Foo",
+            "Unit": "Percent",
+            "StorageResolution": 60
+          }
+        ]
+      }
+    ]
+  },
+  "executionEnvironment": "",
+  "functionName": "",
+  "functionVersion": "",
+  "logStreamId": "",
+  "memorySize": "",
+  "ServiceName": "",
+  "ServiceType": "AWS::Lambda::Function",
+  "Foo": 27
+}

testdata/traceid.json

@@ -0,0 +1,32 @@
+{
+  "_aws": {
+    "Timestamp": "<<PRESENCE>>",
+    "CloudWatchMetrics": [
+      {
+        "Namespace": "aws-embedded-metrics",
+        "Dimensions": [
+          [
+            "ServiceName",
+            "ServiceType"
+          ]
+        ],
+        "Metrics": [
+          {
+            "Name": "something",
+            "Unit": "Count",
+            "StorageResolution": 60
+          }
+        ]
+      }
+    ]
+  },
+  "executionEnvironment": "",
+  "functionName": "",
+  "functionVersion": "",
+  "logStreamId": "",
+  "memorySize": "",
+  "something": 5,
+  "ServiceName": "",
+  "ServiceType": "AWS::Lambda::Function",
+  "traceId": "something_looks_like_id_with_Sampled=1"
+}