Add unix socket support

cmd/snmp-proxy/snmp-proxy.go

@@ -37,7 +37,11 @@ func main() {
 	requester := snmpproxy.NewGosnmpRequester(mibDataProvider)
 
 	apiListener := snmpproxy.NewApiListener(validator, requester, config.Logger, config.Api.Listen)
-	apiListener.Start()
+
+	err = apiListener.Start()
+	if err != nil {
+		config.Logger.Fatalw("failed to start API listener", zap.Error(err))
+	}
 
 	signals := make(chan os.Signal, 1)
 	signal.Notify(signals, syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM)

snmpproxy/api.go

@@ -5,7 +5,9 @@ import (
 	"encoding/json"
 	"errors"
 	"io/ioutil"
+	"net"
 	"net/http"
+	"strings"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
@@ -21,15 +23,32 @@ type ApiListener struct {
 	server    *http.Server
 }
 
-func (l *ApiListener) Start() {
+func (l *ApiListener) Start() error {
+	var (
+		ln  net.Listener
+		err error
+	)
+
+	if strings.HasSuffix(l.server.Addr, ".sock") {
+		ln, err = net.Listen("unix", l.server.Addr)
+	} else {
+		ln, err = net.Listen("tcp", l.server.Addr)
+	}
+
+	if err != nil {
+		return err
+	}
+
 	go func() {
-		err := l.server.ListenAndServe()
+		err := l.server.Serve(ln)
 		if !errors.Is(err, http.ErrServerClosed) {
-			l.logger.Fatalw("failed to start API listener", zap.Error(err))
+			l.logger.Fatalw("http.Serve error", zap.Error(err))
 		}
 	}()
 
 	l.logger.Info("API listener started")
+
+	return nil
 }
 
 func (l *ApiListener) ServeHTTP(writer http.ResponseWriter, request *http.Request) {

snmpproxy/api_test.go

@@ -1,11 +1,14 @@
 package snmpproxy_test
 
 import (
+	"context"
 	"errors"
 	"io"
 	"io/ioutil"
+	"net"
 	"net/http"
 	"net/http/httptest"
+	"os"
 	"strings"
 	"testing"
 	"time"
@@ -232,6 +235,57 @@ func TestStartAndClose(t *testing.T) {
 	require.Error(err)
 }
 
+func TestStartAndCloseOnSocket(t *testing.T) {
+	require := require.New(t)
+
+	prometheus.DefaultRegisterer = prometheus.NewRegistry()
+
+	requester := &mockRequester{}
+	defer requester.AssertExpectations(t)
+
+	requester.On("ExecuteRequest", mock.Anything).Once().Return([][]interface{}{{".1.2.3", 123}}, nil)
+
+	f, err := ioutil.TempFile("", "snmp-proxy-test-*.sock")
+	require.NoError(err)
+	require.NoError(f.Close())
+	require.NoError(os.Remove(f.Name()))
+
+	listener := snmpproxy.NewApiListener(newValidator(), requester, zap.NewNop().Sugar(), f.Name())
+	err = listener.Start()
+	require.NoError(err)
+
+	time.Sleep(time.Millisecond * 10)
+
+	client := http.Client{
+		Transport: &http.Transport{
+			DialContext: func(context.Context, string, string) (net.Conn, error) {
+				return net.Dial("unix", f.Name())
+			},
+		},
+	}
+
+	response, err := client.Post("http://socket/snmp-proxy", "", strings.NewReader(getRequestBody))
+	require.NoError(err)
+	require.Equal(http.StatusOK, response.StatusCode)
+	require.Equal(`{"result":[[".1.2.3",123]]}`, read(response.Body))
+
+	listener.Close()
+
+	response, err = client.Post("http://socket/snmp-proxy", "", strings.NewReader(getRequestBody))
+	require.Nil(response)
+	require.Error(err)
+}
+
+func TestStartError(t *testing.T) {
+	require := require.New(t)
+
+	prometheus.DefaultRegisterer = prometheus.NewRegistry()
+
+	listener := snmpproxy.NewApiListener(newValidator(), &mockRequester{}, zap.NewNop().Sugar(), "localhost:80")
+	err := listener.Start()
+	require.EqualError(err, "listen tcp 127.0.0.1:80: bind: permission denied")
+}
+
 func read(r io.Reader) string {
 	b, err := ioutil.ReadAll(r)
 	if err != nil {