From 727404c9b84dd24f1f94e578613ce091d1a5bfd6 Mon Sep 17 00:00:00 2001
From: Tom Wilkie <tomwilkie@users.noreply.github.com>
Date: Fri, 7 Oct 2016 18:03:36 -0700
Subject: [PATCH] Extend logging middleware to optionally only log failed HTTP
 requests (#1909)

* Extend logging middleware to optionally only log failed HTTP requests

* Add a preconfigured logger for logging failed requests, use it in the app.

* Wide definition of success
---
 common/middleware/logging.go | 27 +++++++++++++++++++++++----
 prog/app.go                  |  2 +-
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/common/middleware/logging.go b/common/middleware/logging.go
index 8bdcc622c..7bda6377f 100644
--- a/common/middleware/logging.go
+++ b/common/middleware/logging.go
@@ -10,16 +10,35 @@ import (
 	log "github.com/Sirupsen/logrus"
 )
 
-// Logging middleware logs each HTTP request method, path, response code and duration.
-var Logging = Func(func(next http.Handler) http.Handler {
+// Log middleware logs http requests
+type Log struct {
+	LogSuccess bool // LogSuccess true -> log successful queries; false -> only log failed queries
+}
+
+// Wrap implements Middleware
+func (l Log) Wrap(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		begin := time.Now()
 		uri := r.RequestURI // capture the URI before running next, as it may get rewritten
 		i := &interceptor{ResponseWriter: w, statusCode: http.StatusOK}
 		next.ServeHTTP(i, r)
-		log.Infof("%s %s (%d) %s", r.Method, uri, i.statusCode, time.Since(begin))
+		if l.LogSuccess || !(100 <= i.statusCode && i.statusCode < 400) {
+			log.Infof("%s %s (%d) %s", r.Method, uri, i.statusCode, time.Since(begin))
+		}
 	})
-})
+}
+
+// Logging middleware logs each HTTP request method, path, response code and
+// duration for all HTTP requests.
+var Logging = Log{
+	LogSuccess: true,
+}
+
+// LogFailed middleware logs each HTTP request method, path, response code and
+// duration for non-2xx HTTP requests.
+var LogFailed = Log{
+	LogSuccess: false,
+}
 
 // interceptor implements WriteHeader to intercept status codes. WriteHeader
 // may not be called on success, so initialize statusCode with the status you
diff --git a/prog/app.go b/prog/app.go
index dfba8e16a..a830c3525 100644
--- a/prog/app.go
+++ b/prog/app.go
@@ -269,7 +269,7 @@ func appMain(flags appFlags) {
 
 	handler := router(collector, controlRouter, pipeRouter, flags.externalUI)
 	if flags.logHTTP {
-		handler = middleware.Logging.Wrap(handler)
+		handler = middleware.LogFailed.Wrap(handler)
 	}
 
 	server := &graceful.Server{