Improve IPFIX collector (#338)

1. Disable printing records whenever we receive them. Instead, we store records in a string array.
2. Add http listener and handler to receive request to return or reset records.

Signed-off-by: Yun-Tang Hsu <hsuy@vmware.com>

cmd/collector/collector.go

@@ -16,11 +16,15 @@ package main
 
 import (
 	"bytes"
+	"context"
+	"encoding/json"
 	"flag"
 	"fmt"
+	"net/http"
 	"os"
 	"os/signal"
 	"strconv"
+	"sync"
 	"syscall"
 	"time"
 
@@ -42,6 +46,8 @@ var (
 	IPFIXAddr      string
 	IPFIXPort      uint16
 	IPFIXTransport string
+	flowRecords    []string
+	mutex          sync.Mutex
 )
 
 func initLoggingToFile(fs *pflag.FlagSet) {
@@ -60,7 +66,7 @@ func addIPFIXFlags(fs *pflag.FlagSet) {
 	fs.StringVar(&IPFIXTransport, "ipfix.transport", "tcp", "IPFIX collector transport layer")
 }
 
-func printIPFIXMessage(msg *entities.Message) {
+func addIPFIXMessage(msg *entities.Message) {
 	var buf bytes.Buffer
 	fmt.Fprint(&buf, "\nIPFIX-HDR:\n")
 	fmt.Fprintf(&buf, "  version: %v,  Message Length: %v\n", msg.GetVersion(), msg.GetMessageLen())
@@ -126,7 +132,9 @@ func printIPFIXMessage(msg *entities.Message) {
 			}
 		}
 	}
-	klog.Infof(buf.String())
+	mutex.Lock()
+	defer mutex.Unlock()
+	flowRecords = append(flowRecords, buf.String())
 }
 
 func signalHandler(stopCh chan struct{}, messageReceived chan *entities.Message) {
@@ -136,7 +144,7 @@ func signalHandler(stopCh chan struct{}, messageReceived chan *entities.Message)
 	for {
 		select {
 		case msg := <-messageReceived:
-			printIPFIXMessage(msg)
+			addIPFIXMessage(msg)
 		case <-signalCh:
 			close(stopCh)
 			return
@@ -173,13 +181,41 @@ func run() error {
 		}
 	}()
 
+	var server *http.Server
+	// Start the HTTP server in a separate goroutine
+	go func() {
+		mux := http.NewServeMux()
+		mux.HandleFunc("/records", flowRecordHandler)
+		mux.HandleFunc("/reset", resetRecordHandler)
+
+		server = &http.Server{
+			Addr:              ":8080",
+			Handler:           mux,
+			ReadHeaderTimeout: 5 * time.Second,
+		}
+
+		klog.InfoS("Server listening on :8080")
+		if err := server.ListenAndServe(); err != http.ErrServerClosed {
+			klog.Fatalf("ListenAndServe error: %v", err)
+		}
+	}()
+
 	stopCh := make(chan struct{})
 	go signalHandler(stopCh, messageReceived)
 
 	<-stopCh
 	// Stop the collector process
 	cp.Stop()
 	klog.Info("Stopping IPFIX collector")
+	// Create a context with a 5-second timeout
+	shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	// Attempt to gracefully shut down the server
+	if err := server.Shutdown(shutdownCtx); err != nil {
+		klog.ErrorS(err, "Error during server shutdown")
+	} else {
+		klog.InfoS("Server gracefully stopped")
+	}
 	return nil
 }
 
@@ -202,6 +238,41 @@ func newCollectorCommand() *cobra.Command {
 	return cmd
 }
 
+func flowRecordHandler(w http.ResponseWriter, r *http.Request) {
+	if r.Method == "GET" {
+		mutex.Lock()
+		defer mutex.Unlock()
+		// Retrieve data
+		klog.InfoS("Return flow records", "length", len(flowRecords))
+		// Convert data to JSON
+		responseData := map[string]interface{}{"flowRecords": flowRecords}
+		jsonData, err := json.Marshal(responseData)
+		if err != nil {
+			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
+			return
+		}
+		// Set response headers
+		w.Header().Set("Content-Type", "application/json")
+		// Write JSON response
+		w.Write(jsonData)
+	} else {
+		http.Error(w, "Invalid request method", http.StatusMethodNotAllowed)
+	}
+}
+
+func resetRecordHandler(w http.ResponseWriter, r *http.Request) {
+	if r.Method == "POST" {
+		mutex.Lock()
+		defer mutex.Unlock()
+		klog.InfoS("Reset flow records")
+		flowRecords = []string{}
+		w.WriteHeader(http.StatusOK)
+		fmt.Fprint(w, "Flow records successfully reset")
+	} else {
+		http.Error(w, "Invalid request method", http.StatusMethodNotAllowed)
+	}
+}
+
 func main() {
 	logs.InitLogs()
 	defer logs.FlushLogs()