Initial release

src/frontend.go

@@ -0,0 +1,142 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+
+	"github.com/gorilla/mux"
+)
+
+// Frontend exposes statuses over HTTP(S)
+type Frontend struct {
+	backend  Backend
+	host     string
+	port     int
+	certfile string
+	keyfile  string
+}
+
+var backend Backend
+var logFormat string
+
+// Start creates an HTTP server and listen
+func (f *Frontend) Start() error {
+	Debug("creating router")
+	r := mux.NewRouter()
+	r.Use(loggingMiddleware)
+	r.Use(headersMiddleware)
+
+	Debug("registering routes")
+	r.HandleFunc("/health", HealthHandler).Methods("GET")
+	r.HandleFunc("/master", PrimaryHandler).Methods("GET", "OPTIONS")
+	r.HandleFunc("/replica", ReplicaHandler).Methods("GET", "OPTIONS")
+
+	Info("listening on %s", f)
+	var err error
+	if f.certfile != "" && f.keyfile != "" {
+		err = http.ListenAndServeTLS(f.String(), f.certfile, f.keyfile, r)
+	} else {
+		err = http.ListenAndServe(f.String(), r)
+	}
+
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (f *Frontend) String() string {
+	return fmt.Sprintf("%s:%d", f.host, f.port)
+}
+
+// NewFrontend creates a Frontend
+func NewFrontend(config FrontendConfig, b Backend) (*Frontend, error) {
+	backend = b
+	logFormat = config.LogFormat
+	return &Frontend{
+		host:     config.Host,
+		port:     config.Port,
+		certfile: config.Certfile,
+		keyfile:  config.Keyfile,
+	}, nil
+}
+
+// Log requests
+func loggingMiddleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		Info(formatRequest(r, logFormat))
+		next.ServeHTTP(w, r)
+	})
+}
+
+// formatRequest replaces request placeholders for logging purpose
+func formatRequest(r *http.Request, format string) string {
+	if format == "" {
+		format = "%a - %m %U"
+	}
+	definitions := map[string]string{
+		"%a": r.RemoteAddr,
+		"%m": r.Method,
+		"%U": r.RequestURI,
+	}
+	output := format
+
+	for placeholder, value := range definitions {
+		output = strings.Replace(output, placeholder, value, -1)
+	}
+
+	return output
+}
+
+// Add headers
+func headersMiddleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		next.ServeHTTP(w, r)
+	})
+}
+
+// HealthHandler returns frontend health status
+func HealthHandler(w http.ResponseWriter, r *http.Request) {
+	w.WriteHeader(http.StatusOK)
+	io.WriteString(w, `{"healthy": true}`)
+}
+
+// PrimaryHandler exposes primary status
+func PrimaryHandler(w http.ResponseWriter, r *http.Request) {
+	var message string
+	var status int
+	primary, err := backend.IsPrimary()
+	if err != nil {
+		message = fmt.Sprintf("{\"error\":\"%v\"}", err)
+		status = http.StatusServiceUnavailable
+	}
+	message = fmt.Sprintf("{\"primary\":%t}", primary)
+	status = http.StatusServiceUnavailable
+	if primary {
+		status = http.StatusOK
+	}
+	w.WriteHeader(status)
+	io.WriteString(w, message)
+}
+
+// ReplicaHandler exposes replica status
+func ReplicaHandler(w http.ResponseWriter, r *http.Request) {
+	var message string
+	var status int
+	replica, err := backend.IsReplica()
+	if err != nil {
+		message = fmt.Sprintf("{\"error\":\"%v\"}", err)
+		status = http.StatusServiceUnavailable
+	}
+	message = fmt.Sprintf("{\"replica\":%t}", replica)
+	status = http.StatusServiceUnavailable
+	if replica {
+		status = http.StatusOK
+	}
+	w.WriteHeader(status)
+	io.WriteString(w, message)
+}