// Copyright 2021 by the contributors.
//
// Licensed 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 internalserver
import (
"fmt"
"net/http"
"net/http/pprof"
"sort"
"github.com/metalmatze/signal/healthcheck"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promhttp"
)
// Handler is a http.ServeMux that knows about all endpoints to render a nice index page.
type Handler struct {
http.ServeMux
endpoints []endpoint
name string
}
// endpoint has a description to a pattern.
type endpoint struct {
Pattern string
Description string
}
// NewHandler creates a new internalserver Handler.
func NewHandler(options ...Option) *Handler {
h := &Handler{name: "Internal"}
for _, option := range options {
option(h)
}
h.HandleFunc("/", h.index)
return h
}
// AddEndpoint wraps HandleFunc for adding http handlers to add a meaningful description to the index page.
func (h *Handler) AddEndpoint(pattern string, description string, handler http.HandlerFunc) {
h.endpoints = append(h.endpoints, endpoint{
Pattern: pattern,
Description: description,
})
// Sort endpoints by pattern after adding a new one, to always show them in the same order.
sort.Slice(h.endpoints, func(i, j int) bool {
return h.endpoints[i].Pattern < h.endpoints[j].Pattern
})
h.HandleFunc(pattern, handler)
}
func (h *Handler) index(w http.ResponseWriter, r *http.Request) {
html := fmt.Sprintf("%s\n", h.name)
html += fmt.Sprintf("%s
\n", h.name)
for _, e := range h.endpoints {
html += fmt.Sprintf("%s - %s
\n", e.Pattern, e.Pattern, e.Description)
}
html += ``
w.Header().Set("Content-Type", "text/html; charset=utf-8")
_, _ = w.Write([]byte(html))
}
// Option is a func that modifies the configuration for the internalserver handler.
type Option func(h *Handler)
// WithName allows to set an application name for the internalserver handler.
func WithName(name string) Option {
return func(h *Handler) {
h.name = name
}
}
// WithHealthchecks adds the healthchecks endpoints /live and /ready to the internalserver.
func WithHealthchecks(healthchecks healthcheck.Handler) Option {
return func(h *Handler) {
h.AddEndpoint(
"/live",
"Exposes liveness checks",
healthchecks.LiveEndpoint,
)
h.AddEndpoint(
"/ready",
"Exposes readiness checks",
healthchecks.ReadyEndpoint,
)
}
}
// WithPrometheusRegistry adds a /metrics endpoint to the internalserver.
func WithPrometheusRegistry(registry *prometheus.Registry) Option {
return func(h *Handler) {
h.AddEndpoint(
"/metrics",
"Exposes Prometheus metrics",
promhttp.HandlerFor(registry, promhttp.HandlerOpts{}).ServeHTTP,
)
}
}
// WithPProf adds all pprof endpoints under /debug to the internalserver.
func WithPProf() Option {
return func(h *Handler) {
m := http.NewServeMux()
m.HandleFunc("/debug/pprof/", pprof.Index)
m.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline)
m.HandleFunc("/debug/pprof/profile", pprof.Profile)
m.HandleFunc("/debug/pprof/symbol", pprof.Symbol)
m.HandleFunc("/debug/pprof/trace", pprof.Trace)
m.HandleFunc("/debug/", func(w http.ResponseWriter, r *http.Request) {
http.Redirect(w, r, "/debug/pprof/", http.StatusMovedPermanently)
})
h.AddEndpoint(
"/debug/",
"Exposes pprof endpoints to consume via HTTP",
m.ServeHTTP,
)
}
}