internal/beater/api/expvar.go

// Licensed to Elasticsearch B.V. under one or more contributor
// license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright
// ownership. Elasticsearch B.V. licenses this file to you under
// the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

package api

import (
	"expvar"
	"fmt"
	"net/http"

	"github.com/elastic/elastic-agent-libs/monitoring"
)

// debugVarsHandler reports expvar and all libbeat/monitoring metrics.
//
// TODO(axw) this is copied from libbeat/service. We should move the
// handler to libbeat/monitoring, and export it for libbeat/service and
// apm-server to use.
func debugVarsHandler(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")

	first := true
	report := func(key string, value interface{}) {
		if !first {
			fmt.Fprintf(w, ",\n")
		}
		first = false
		if str, ok := value.(string); ok {
			fmt.Fprintf(w, "%q: %q", key, str)
		} else {
			fmt.Fprintf(w, "%q: %v", key, value)
		}
	}

	fmt.Fprintf(w, "{\n")
	monitoring.Do(monitoring.Full, report)
	expvar.Do(func(kv expvar.KeyValue) {
		report(kv.Key, kv.Value)
	})
	fmt.Fprintf(w, "\n}\n")
}