add ability to stream command output as a response

internal/hook/hook.go

@@ -570,6 +570,7 @@ type Hook struct {
 	ResponseMessage                     string          `json:"response-message,omitempty"`
 	ResponseHeaders                     ResponseHeaders `json:"response-headers,omitempty"`
 	CaptureCommandOutput                bool            `json:"include-command-output-in-response,omitempty"`
+	StreamCommandOutput 				bool 			`json:"stream-command-output,omitempty"`
 	CaptureCommandOutputOnError         bool            `json:"include-command-output-in-response-on-error,omitempty"`
 	PassEnvironmentToCommand            []Argument      `json:"pass-environment-to-command,omitempty"`
 	PassArgumentsToCommand              []Argument      `json:"pass-arguments-to-command,omitempty"`

webhook.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"flag"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"log"
 	"net"
@@ -63,6 +64,19 @@ var (
 	pidFile *pidfile.PIDFile
 )
 
+type flushWriter struct {
+	f http.Flusher
+	w io.Writer
+}
+
+func (fw *flushWriter) Write(p []byte) (n int, err error) {
+	n, err = fw.w.Write(p)
+	if fw.f != nil {
+		fw.f.Flush()
+	}
+	return
+}
+
 func matchLoadedHook(id string) *hook.Hook {
 	for _, hooks := range loadedHooksFromFiles {
 		if hook := hooks.Match(id); hook != nil {
@@ -504,8 +518,10 @@ func hookHandler(w http.ResponseWriter, r *http.Request) {
 			w.Header().Set(responseHeader.Name, responseHeader.Value)
 		}
 
-		if matchedHook.CaptureCommandOutput {
-			response, err := handleHook(matchedHook, req)
+		if matchedHook.StreamCommandOutput {
+			handleHook(matchedHook, req, w)
+		} else if matchedHook.CaptureCommandOutput {
+			response, err := handleHook(matchedHook, req, nil)
 
 			if err != nil {
 				w.WriteHeader(http.StatusInternalServerError)
@@ -523,7 +539,7 @@ func hookHandler(w http.ResponseWriter, r *http.Request) {
 				fmt.Fprint(w, response)
 			}
 		} else {
-			go handleHook(matchedHook, req)
+			go handleHook(matchedHook, req, nil)
 
 			// Check if a success return code is configured for the hook
 			if matchedHook.SuccessHttpResponseCode != 0 {
@@ -546,7 +562,7 @@ func hookHandler(w http.ResponseWriter, r *http.Request) {
 	fmt.Fprint(w, "Hook rules were not satisfied.")
 }
 
-func handleHook(h *hook.Hook, r *hook.Request) (string, error) {
+func handleHook(h *hook.Hook, r *hook.Request, w http.ResponseWriter) (string, error) {
 	var errors []error
 
 	// check the command exists
@@ -615,13 +631,31 @@ func handleHook(h *hook.Hook, r *hook.Request) (string, error) {
 
 	log.Printf("[%s] executing %s (%s) with arguments %q and environment %s using %s as cwd\n", r.ID, h.ExecuteCommand, cmd.Path, cmd.Args, envs, cmd.Dir)
 
-	out, err := cmd.CombinedOutput()
+	var out []byte
+	if w != nil {
+		log.Printf("[%s] command output will be streamed to response", r.ID)
+
+		// Implementation from https://play.golang.org/p/PpbPyXbtEs
+		// as described in https://stackoverflow.com/questions/19292113/not-buffered-http-responsewritter-in-golang
+		fw := flushWriter{w: w}
+		if f, ok := w.(http.Flusher); ok {
+			fw.f = f
+		}
+		cmd.Stderr = &fw
+		cmd.Stdout = &fw
+
+		if err := cmd.Run(); err != nil {
+			log.Printf("[%s] error occurred: %+v\n", r.ID, err)
+		}
+	} else {
+		out, err = cmd.CombinedOutput()
 
 		log.Printf("[%s] command output: %s\n", r.ID, out)
 
 		if err != nil {
 			log.Printf("[%s] error occurred: %+v\n", r.ID, err)
 		}
+	}
 
 	for i := range files {
 		if files[i].File != nil {

webhook_test.go

@@ -58,7 +58,7 @@ func TestStaticParams(t *testing.T) {
 		ID:      "test",
 		Headers: spHeaders,
 	}
-	_, err = handleHook(spHook, r)
+	_, err = handleHook(spHook, r, nil)
 	if err != nil {
 		t.Fatalf("Unexpected error: %v\n", err)
 	}