Merge pull request hound-search#297 from etsy/health-check

Add the ability to respond to health checks prior to indexes being built.

cmds/houndd/main.go

@@ -17,6 +17,7 @@ import (
 	"github.com/etsy/hound/config"
 	"github.com/etsy/hound/searcher"
 	"github.com/etsy/hound/ui"
+	"github.com/etsy/hound/web"
 )
 
 const gracefulShutdownSignal = syscall.SIGTERM
@@ -128,6 +129,9 @@ func main() {
 		panic(err)
 	}
 
+	// Start the web server on a background routine.
+	ws := web.Start(&cfg, *flagAddr, *flagDev)
+
 	// It's not safe to be killed during makeSearchers, so register the
 	// shutdown signal here and defer processing it until we are ready.
 	shutdownCh := registerShutdownSignal()
@@ -162,7 +166,6 @@ func main() {
 
 	info_log.Printf("running server at http://%s...\n", host)
 
-	if err := runHttp(*flagAddr, *flagDev, &cfg, idx); err != nil {
-		panic(err)
-	}
+	// Fully enable the web server now that we have indexes
+	panic(ws.ServeWithIndex(idx))
 }

config/config.go

@@ -15,6 +15,7 @@ const (
 	defaultVcs                   = "git"
 	defaultBaseUrl               = "{url}/blob/master/{path}{anchor}"
 	defaultAnchor                = "#L{line}"
+	defaultHealthChekURI         = "/healthz"
 )
 
 type UrlPattern struct {
@@ -56,6 +57,7 @@ type Config struct {
 	DbPath                string           `json:"dbpath"`
 	Repos                 map[string]*Repo `json:"repos"`
 	MaxConcurrentIndexers int              `json:"max-concurrent-indexers"`
+	HealthCheckURI        string           `json:"health-check-uri"`
 }
 
 // SecretMessage is just like json.RawMessage but it will not
@@ -117,6 +119,10 @@ func initConfig(c *Config) {
 	if c.MaxConcurrentIndexers == 0 {
 		c.MaxConcurrentIndexers = defaultMaxConcurrentIndexers
 	}
+
+	if c.HealthCheckURI == "" {
+		c.HealthCheckURI = defaultHealthChekURI
+	}
 }
 
 func (c *Config) LoadFromFile(filename string) error {

web/web.go

@@ -0,0 +1,85 @@
+package web
+
+import (
+	"fmt"
+	"net/http"
+	"sync"
+
+	"github.com/etsy/hound/api"
+	"github.com/etsy/hound/config"
+	"github.com/etsy/hound/searcher"
+	"github.com/etsy/hound/ui"
+)
+
+// Server is an HTTP server that handles all
+// http traffic for hound. It is able to serve
+// some traffic before indexes are built and
+// then transition to all traffic afterwards.
+type Server struct {
+	cfg *config.Config
+	dev bool
+	ch  chan error
+
+	mux *http.ServeMux
+	lck sync.RWMutex
+}
+
+func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if r.URL.Path == s.cfg.HealthCheckURI {
+		fmt.Fprintln(w, "👍")
+		return
+	}
+
+	s.lck.RLock()
+	defer s.lck.RUnlock()
+	if m := s.mux; m != nil {
+		m.ServeHTTP(w, r)
+	} else {
+		http.Error(w,
+			"Hound is not ready.",
+			http.StatusServiceUnavailable)
+	}
+}
+
+func (s *Server) serveWith(m *http.ServeMux) {
+	s.lck.Lock()
+	defer s.lck.Unlock()
+	s.mux = m
+}
+
+// Start creates a new server that will immediately start handling HTTP traffic.
+// The HTTP server will return 200 on the health check, but a 503 on every other
+// request until ServeWithIndex is called to begin serving search traffic with
+// the given searchers.
+func Start(cfg *config.Config, addr string, dev bool) *Server {
+	ch := make(chan error)
+
+	s := &Server{
+		cfg: cfg,
+		dev: dev,
+		ch:  ch,
+	}
+
+	go func() {
+		ch <- http.ListenAndServe(addr, s)
+	}()
+
+	return s
+}
+
+// ServeWithIndex allow the server to start offering the search UI and the
+// search APIs operating on the given indexes.
+func (s *Server) ServeWithIndex(idx map[string]*searcher.Searcher) error {
+	h, err := ui.Content(s.dev, s.cfg)
+	if err != nil {
+		return err
+	}
+
+	m := http.NewServeMux()
+	m.Handle("/", h)
+	api.Setup(m, idx)
+
+	s.serveWith(m)
+
+	return <-s.ch
+}