example: using prometheus tags in custom metrics (#246)

e2e/e2e_test.go

@@ -169,29 +169,44 @@ func Test_http_routing(t *testing.T) {
 func Test_metrics(t *testing.T) {
 	_, kill := startEnvoy(t, 8001)
 	defer kill()
-	var count int
-	require.Eventually(t, func() bool {
-		res, err := http.Get("http://localhost:18000")
-		if err != nil {
-			return false
-		}
-		defer res.Body.Close()
-		if res.StatusCode != http.StatusOK {
-			return false
-		}
-		count++
-		return count == 10
-	}, 5*time.Second, time.Millisecond, "Endpoint not healthy.")
-	require.Eventually(t, func() bool {
-		res, err := http.Get("http://localhost:8001/stats/prometheus")
-		if err != nil {
-			return false
-		}
-		defer res.Body.Close()
-		raw, err := io.ReadAll(res.Body)
-		require.NoError(t, err)
-		return checkMessage(string(raw), []string{fmt.Sprintf("proxy_wasm_go_request_counter{} %d", count)}, nil)
-	}, 5*time.Second, time.Millisecond, "Expected stats not found")
+
+	const customHeaderKey = "my-custom-header"
+	customHeaderToExpectedCounts := map[string]int{
+		"foo": 3,
+		"bar": 5,
+	}
+	for headerValue, expCount := range customHeaderToExpectedCounts {
+		var actualCount int
+		require.Eventually(t, func() bool {
+			req, err := http.NewRequest("GET", "http://localhost:18000", nil)
+			require.NoError(t, err)
+			req.Header.Add(customHeaderKey, headerValue)
+			res, err := http.DefaultClient.Do(req)
+			if err != nil {
+				return false
+			}
+			defer res.Body.Close()
+			if res.StatusCode != http.StatusOK {
+				return false
+			}
+			actualCount++
+			return actualCount == expCount
+		}, 5*time.Second, time.Millisecond, "Endpoint not healthy.")
+	}
+
+	for headerValue, expCount := range customHeaderToExpectedCounts {
+		expectedMetric := fmt.Sprintf("custom_header_value_counts{value=\"%s\",reporter=\"wasmgosdk\"} %d", headerValue, expCount)
+		require.Eventually(t, func() bool {
+			res, err := http.Get("http://localhost:8001/stats/prometheus")
+			if err != nil {
+				return false
+			}
+			defer res.Body.Close()
+			raw, err := io.ReadAll(res.Body)
+			require.NoError(t, err)
+			return checkMessage(string(raw), []string{expectedMetric}, nil)
+		}, 5*time.Second, time.Millisecond, "Expected stats not found")
+	}
 }
 
 func Test_network(t *testing.T) {

examples/metrics/README.md

@@ -1,25 +1,12 @@
 
 ## metrics
 
-this example creates simple request counter
+this example creates simple request counter with prometheus tags.
 
 ```
-wasm log: previous value of proxy_wasm_go.request_counter: 0
-wasm log: incremented
-wasm log: previous value of proxy_wasm_go.request_counter: 1
-wasm log: incremented
-wasm log: previous value of proxy_wasm_go.request_counter: 2
-wasm log: incremented
-wasm log: previous value of proxy_wasm_go.request_counter: 3
-wasm log: incremented
-wasm log: previous value of proxy_wasm_go.request_counter: 4
-wasm log: incremented
-wasm log: previous value of proxy_wasm_go.request_counter: 5
-wasm log: incremented
-```
+$ curl localhost:18000 -v -H "my-custom-header: foo" 
 
-```
 $ curl -s 'localhost:8001/stats/prometheus'| grep proxy
-# TYPE proxy_wasm_go_request_counter counter
-proxy_wasm_go_request_counter{} 5
+# TYPE custom_header_value_counts counter
+custom_header_value_counts{value="foo",reporter="wasmgosdk"} 1
 ```

examples/metrics/envoy.yaml

@@ -1,3 +1,13 @@
+stats_config:
+  stats_tags:
+    # Envoy extracs the first matching group as a value.
+    # This case, the part ([a-zA-Z]+) is extracted as a value for "value" tag.
+    # See https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/metrics/v3/stats.proto#config-metrics-v3-statsconfig.
+    - tag_name: value
+      regex: '(_value=([a-zA-Z]+))'
+    - tag_name: reporter
+      regex: '(_reporter=([a-zA-Z]+))'
+
 static_resources:
   listeners:
     - name: main

examples/metrics/main.go

@@ -15,6 +15,8 @@
 package main
 
 import (
+	"fmt"
+
 	"github.com/tetratelabs/proxy-wasm-go-sdk/proxywasm"
 	"github.com/tetratelabs/proxy-wasm-go-sdk/proxywasm/types"
 )
@@ -31,36 +33,47 @@ type vmContext struct {
 
 // Override types.DefaultVMContext.
 func (*vmContext) NewPluginContext(contextID uint32) types.PluginContext {
-	return &metricPluginContext{
-		counter: proxywasm.DefineCounterMetric("proxy_wasm_go.request_counter"),
-	}
+	return &metricPluginContext{}
 }
 
 type metricPluginContext struct {
 	// Embed the default plugin context here,
 	// so that we don't need to reimplement all the methods.
 	types.DefaultPluginContext
-	counter proxywasm.MetricCounter
 }
 
 // Override types.DefaultPluginContext.
 func (ctx *metricPluginContext) NewHttpContext(contextID uint32) types.HttpContext {
-	return &metricHttpContext{counter: ctx.counter}
+	return &metricHttpContext{}
 }
 
 type metricHttpContext struct {
 	// Embed the default http context here,
 	// so that we don't need to reimplement all the methods.
 	types.DefaultHttpContext
-	counter proxywasm.MetricCounter
 }
 
+const (
+	customHeaderKey         = "my-custom-header"
+	customHeaderValueTagKey = "value"
+)
+
+var counters = map[string]proxywasm.MetricCounter{}
+
 // Override types.DefaultHttpContext.
 func (ctx *metricHttpContext) OnHttpRequestHeaders(numHeaders int, endOfStream bool) types.Action {
-	prev := ctx.counter.Value()
-	proxywasm.LogInfof("previous value of %s: %d", "proxy_wasm_go.request_counter", prev)
-
-	ctx.counter.Increment(1)
-	proxywasm.LogInfo("incremented")
+	customHeaderValue, err := proxywasm.GetHttpRequestHeader(customHeaderKey)
+	if err == nil {
+		counter, ok := counters[customHeaderValue]
+		if !ok {
+			// This metric is processed as: custom_header_value_counts{value="foo",reporter="wasmgosdk"} n.
+			// The extraction rule is defined in envoy.yaml as a bootstrap configuration.
+			// See https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/metrics/v3/stats.proto#config-metrics-v3-statsconfig.
+			fqn := fmt.Sprintf("custom_header_value_counts_%s=%s_reporter=wasmgosdk", customHeaderValueTagKey, customHeaderValue)
+			counter = proxywasm.DefineCounterMetric(fqn)
+			counters[customHeaderValue] = counter
+		}
+		counter.Increment(1)
+	}
 	return types.ActionContinue
 }

examples/metrics/main_test.go

@@ -25,20 +25,17 @@ func TestMetric(t *testing.T) {
 	require.Equal(t, types.OnVMStartStatusOK, host.StartVM())
 
 	// Initialize http context.
+	headers := [][2]string{{"my-custom-header", "foo"}}
 	contextID := host.InitializeHttpContext()
 	exp := uint64(3)
 	for i := uint64(0); i < exp; i++ {
 		// Call OnRequestHeaders
-		action := host.CallOnRequestHeaders(contextID, nil, false)
+		action := host.CallOnRequestHeaders(contextID, headers, false)
 		require.Equal(t, types.ActionContinue, action)
 	}
 
-	// Check Envoy logs.
-	logs := host.GetInfoLogs()
-	require.Contains(t, logs, "incremented")
-
 	// Check metrics.
-	value, err := host.GetCounterMetric("proxy_wasm_go.request_counter")
+	value, err := host.GetCounterMetric("custom_header_value_counts_value=foo_reporter=wasmgosdk")
 	require.NoError(t, err)
 	require.Equal(t, uint64(3), value)
 }