From b7fd1f4e9ea044566e246b0768f2254238400d3e Mon Sep 17 00:00:00 2001
From: Abiola Ibrahim <abiola89@gmail.com>
Date: Sat, 12 Dec 2015 14:04:48 +0100
Subject: [PATCH] FastCGI: separate standard and error output responses.

---
 middleware/fastcgi/fastcgi.go    | 15 ++++++++++++++-
 middleware/fastcgi/fcgiclient.go | 21 +++++++++++++++++----
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/middleware/fastcgi/fastcgi.go b/middleware/fastcgi/fastcgi.go
index 77fb668f..b7a86b66 100755
--- a/middleware/fastcgi/fastcgi.go
+++ b/middleware/fastcgi/fastcgi.go
@@ -115,7 +115,12 @@ func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error)
 				return http.StatusBadGateway, err
 			}
 
-			return 0, nil
+			// FastCGI stderr outputs
+			if fcgi.stderr.Len() != 0 {
+				err = LogError(fcgi.stderr.String())
+			}
+
+			return 0, err
 		}
 	}
 
@@ -281,3 +286,11 @@ var (
 	// ErrIndexMissingSplit describes an index configuration error.
 	ErrIndexMissingSplit = errors.New("configured index file(s) must include split value")
 )
+
+// LogError is a non fatal error that allows requests to go through.
+type LogError string
+
+// Error satisfies error interface.
+func (l LogError) Error() string {
+	return string(l)
+}
diff --git a/middleware/fastcgi/fcgiclient.go b/middleware/fastcgi/fcgiclient.go
index b8b03fe7..97dc6153 100644
--- a/middleware/fastcgi/fcgiclient.go
+++ b/middleware/fastcgi/fcgiclient.go
@@ -164,6 +164,7 @@ type FCGIClient struct {
 	rwc       io.ReadWriteCloser
 	h         header
 	buf       bytes.Buffer
+	stderr    bytes.Buffer
 	keepAlive bool
 	reqID     uint16
 }
@@ -346,10 +347,22 @@ func (w *streamReader) Read(p []byte) (n int, err error) {
 
 	if len(p) > 0 {
 		if len(w.buf) == 0 {
-			rec := &record{}
-			w.buf, err = rec.read(w.c.rwc)
-			if err != nil {
-				return
+
+			// filter outputs for error log
+			for {
+				rec := &record{}
+				var buf []byte
+				buf, err = rec.read(w.c.rwc)
+				if err != nil {
+					return
+				}
+				// standard error output
+				if rec.h.Type == Stderr {
+					w.c.stderr.Write(buf)
+					continue
+				}
+				w.buf = buf
+				break
 			}
 		}