Log time/version to startup log (Fixes #391)

holder.go

@@ -547,6 +547,28 @@ func (h *Holder) loadNodeID() (string, error) {
 	return nodeID, nil
 }
 
+// Log startup time and version to $DATA_DIR/.startup.log
+func (h *Holder) logStartup() error {
+	time, err := time.Now().MarshalText()
+	if err != nil {
+		return errors.Wrap(err, "creating timestamp")
+	}
+	logLine := fmt.Sprintf("%s\t%s\n", time, Version)
+
+	f, err := os.OpenFile(h.Path+"/.startup.log", os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0600)
+	if err != nil {
+		return errors.Wrap(err, "opening startup log")
+	}
+
+	defer f.Close()
+
+	if _, err = f.WriteString(logLine); err != nil {
+		return errors.Wrap(err, "writing startup log")
+	}
+
+	return nil
+}
+
 // HolderSyncer is an active anti-entropy tool that compares the local holder
 // with a remote holder based on block checksums and resolves differences.
 type HolderSyncer struct {

server.go

@@ -17,6 +17,7 @@ package pilosa
 import (
 	"context"
 	"fmt"
+	"log"
 	"net"
 	"net/http"
 	"os"
@@ -268,6 +269,12 @@ func (s *Server) Open() error {
 		return errors.New("Must pass a listener option to NewServer")
 	}
 
+	// Log startup
+	err := s.Holder.logStartup()
+	if err != nil {
+		log.Println(errors.Wrap(err, "logging startup"))
+	}
+
 	// Get or create NodeID.
 
 	// Append the NodeID tag to stats.