fasthttputil: added ExpvarHandler for serving variables exported via standard expvar package

3 files changed, 71 insertions, 0 deletions

diff --git a/fasthttputil/doc.go b/fasthttputil/doc.go
new file mode 100644
index 0000000..9cf69e7
--- /dev/null
+++ b/fasthttputil/doc.go
@@ -0,0 +1,2 @@
+// Package fasthttputil provides utility functions for fasthttp.
+package fasthttputil
diff --git a/fasthttputil/expvar.go b/fasthttputil/expvar.go
new file mode 100644
index 0000000..b2679a2
--- /dev/null
+++ b/fasthttputil/expvar.go
@@ -0,0 +1,28 @@
+package fasthttputil
+
+import (
+	"expvar"
+	"fmt"
+
+	"github.com/valyala/fasthttp"
+)
+
+// ExpvarHandler dumps json representation of expvars to http response.
+//
+// See https://golang.org/pkg/expvar/ for details.
+func ExpvarHandler(ctx *fasthttp.RequestCtx) {
+	ctx.Response.Reset()
+
+	fmt.Fprintf(ctx, "{\n")
+	first := true
+	expvar.Do(func(kv expvar.KeyValue) {
+		if !first {
+			fmt.Fprintf(ctx, ",\n")
+		}
+		first = false
+		fmt.Fprintf(ctx, "%q: %s", kv.Key, kv.Value)
+	})
+	fmt.Fprintf(ctx, "\n}\n")
+
+	ctx.SetContentType("application/json; charset=utf-8")
+}
diff --git a/fasthttputil/expvar_test.go b/fasthttputil/expvar_test.go
new file mode 100644
index 0000000..4c409a0
--- /dev/null
+++ b/fasthttputil/expvar_test.go
@@ -0,0 +1,41 @@
+package fasthttputil
+
+import (
+	"encoding/json"
+	"expvar"
+	"testing"
+
+	"github.com/valyala/fasthttp"
+)
+
+func TestExpvarHandler(t *testing.T) {
+	expvar.Publish("customVar", expvar.Func(func() interface{} {
+		return "foobar"
+	}))
+
+	var ctx fasthttp.RequestCtx
+
+	ExpvarHandler(&ctx)
+
+	body := ctx.Response.Body()
+
+	var m map[string]interface{}
+	if err := json.Unmarshal(body, &m); err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+
+	if _, ok := m["cmdline"]; !ok {
+		t.Fatalf("cannot locate cmdline expvar")
+	}
+	if _, ok := m["memstats"]; !ok {
+		t.Fatalf("cannot locate memstats expvar")
+	}
+
+	v, ok := m["customVar"]
+	if !ok {
+		t.Fatalf("cannot locate customVar")
+	}
+	if v != "foobar" {
+		t.Fatalf("unexpected custom var value: %q. Expecting %q", v, "foobar")
+	}
+}