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api.go
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api.go
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// Copyright 2022 Block, Inc.
package server
import (
"context"
"encoding/json"
"fmt"
"html"
"net/http"
"runtime"
"strings"
"time"
"gopkg.in/yaml.v2"
"github.com/cashapp/blip"
"github.com/cashapp/blip/event"
"github.com/cashapp/blip/metrics"
"github.com/cashapp/blip/monitor"
"github.com/cashapp/blip/sink"
"github.com/cashapp/blip/status"
)
type API struct {
cfg blip.Config
monitorLoader *monitor.Loader
// --
httpServer *http.Server
startTs time.Time
}
func NewAPI(cfg blip.Config, ml *monitor.Loader) *API {
api := &API{
cfg: cfg,
monitorLoader: ml,
}
mux := http.NewServeMux()
mux.HandleFunc("/config", api.config)
mux.HandleFunc("/registered", api.registered)
mux.HandleFunc("/version", api.version)
mux.HandleFunc("/monitors", api.monitors)
mux.HandleFunc("/monitors/stop", api.monitorsStop)
mux.HandleFunc("/monitors/start", api.monitorsStart)
mux.HandleFunc("/monitors/reload", api.monitorsReload)
mux.HandleFunc("/status", api.status)
mux.HandleFunc("/status/monitors", api.statusMonitors)
api.httpServer = &http.Server{
Addr: cfg.API.Bind,
Handler: mux,
}
return api
}
// ServeHTTP allows the API to statisfy the http.HandlerFunc interface.
func (api *API) ServeHTTP(w http.ResponseWriter, r *http.Request) {
api.httpServer.Handler.ServeHTTP(w, r)
}
// Run runs the API and restarts on error.
func (api *API) Run() error {
api.startTs = time.Now()
errChan := make(chan error, 1)
for {
go func() {
var serr error // http Sever error
defer func() { // catch panic
if r := recover(); r != nil {
b := make([]byte, 4096)
n := runtime.Stack(b, false)
serr = fmt.Errorf("PANIC: server API: %s\n%s", r, string(b[0:n]))
}
errChan <- serr
}()
blip.Debug("listen")
serr = api.httpServer.ListenAndServe()
}()
err := <-errChan
switch err {
case http.ErrServerClosed:
blip.Debug("shutdown")
return nil
default:
event.Errorf(event.SERVER_API_ERROR, err.Error())
time.Sleep(1 * time.Second) // between crashes
}
}
}
// --------------------------------------------------------------------------
// Blip endpoints
// --------------------------------------------------------------------------
func (api *API) config(w http.ResponseWriter, r *http.Request) {
blip.Debug("%v", r)
q := r.URL.Query()
if q.Has("json") {
json.NewEncoder(w).Encode(api.cfg)
} else {
yaml.NewEncoder(w).Encode(api.cfg)
}
}
type registeredList struct {
Collectors []string `json:"collectors"`
Sinks []string `json:"sinks"`
}
func (api *API) registered(w http.ResponseWriter, r *http.Request) {
blip.Debug("%v", r)
rl := registeredList{
Collectors: metrics.List(),
Sinks: sink.List(),
}
json.NewEncoder(w).Encode(rl)
}
func (api *API) version(w http.ResponseWriter, r *http.Request) {
blip.Debug("%v", r)
w.Write([]byte(blip.VERSION))
}
// --------------------------------------------------------------------------
// Monitor endpoints
// --------------------------------------------------------------------------
func (api *API) monitors(w http.ResponseWriter, r *http.Request) {
blip.Debug("%v", r)
ml := map[string]string{}
m := api.monitorLoader.Monitors()
for i := range m {
ml[m[i].MonitorId()] = m[i].DSN() // redacted
}
json.NewEncoder(w).Encode(ml)
}
func (api *API) monitorsReload(w http.ResponseWriter, r *http.Request) {
blip.Debug("%v", r)
if err := api.monitorLoader.Load(context.Background()); err != nil {
switch err {
case monitor.ErrStopLoss:
http.Error(w, "Stop-loss prevented reloading; see Blip error log for details", http.StatusPreconditionFailed)
default:
errMsg := html.EscapeString(fmt.Sprintf("Error reloading monitors: %s", err))
http.Error(w, errMsg, http.StatusConflict)
}
return
}
api.monitorLoader.StartMonitors()
w.WriteHeader(http.StatusOK)
}
func (api *API) monitorsStart(w http.ResponseWriter, r *http.Request) {
blip.Debug("%v", r)
monitorId, mon, ok := api.monitorId(w, r)
if !ok {
return // monitorId() wrote error response
}
blip.Debug("start %s", monitorId)
if err := mon.Start(); err != nil {
errMsg := html.EscapeString(fmt.Sprintf("Error starting monitor %s: %s", html.EscapeString(monitorId), err))
http.Error(w, errMsg, http.StatusConflict)
return
}
w.WriteHeader(http.StatusOK)
}
func (api *API) monitorsStop(w http.ResponseWriter, r *http.Request) {
blip.Debug("%v", r)
monitorId, mon, ok := api.monitorId(w, r)
if !ok {
return // monitorId() wrote error response
}
blip.Debug("stop %s", monitorId)
mon.Stop() // Stopy only returns nil
w.WriteHeader(http.StatusOK)
}
// --------------------------------------------------------------------------
// Status endpoints
// --------------------------------------------------------------------------
func (api *API) status(w http.ResponseWriter, r *http.Request) {
blip.Debug("%v", r)
status.Blip("uptime", "%d", int(time.Since(api.startTs).Seconds()))
json.NewEncoder(w).Encode(status.ReportBlip())
}
func (api *API) statusMonitors(w http.ResponseWriter, r *http.Request) {
blip.Debug("%v", r)
json.NewEncoder(w).Encode(status.ReportMonitors())
}
// --------------------------------------------------------------------------
// Helper funcs
// monitorId returns the monitor ID from URL query param '?id=monitorId' if set.
// Else it returns an empty string and false. The caller must return without
// doing anything else on false because this func writes the HTTP error response
// on false.
func (api *API) monitorId(w http.ResponseWriter, r *http.Request) (string, *monitor.Monitor, bool) {
monitorId := r.URL.Query().Get("id")
if monitorId == "" {
http.Error(w, "missing id=monitorId in query", http.StatusBadRequest)
return "", nil, false
}
mon := api.monitorLoader.Monitor(monitorId)
if mon == nil {
http.Error(w, fmt.Sprintf("monitor %s not loaded", html.EscapeString(monitorId)), http.StatusNotFound)
return "", nil, false
}
// Avoid code scanning alert "Log entries created from user input"
monitorId = strings.Replace(monitorId, "\n", "", -1)
monitorId = strings.Replace(monitorId, "\r", "", -1)
return monitorId, mon, true
}