log: 'except' subdirective to skip logging certain requests (#2028)

* proof of concept

* Initial implementation with debug code

* Tidy up debug code

* remove unneeded import

* removed extra line

* Move ShouldLog function to rule entry Logger type

* add tests for ShouldLog

* Added tests for log exceptions

* Fix logic

* fix govet fail for test

* Updates requested for code clarity

* Update requested for style

* log: Minor style tweaks to logic of log exceptions

4 files changed, 107 insertions, 1 deletions

diff --git a/caddyhttp/httpserver/logger.go b/caddyhttp/httpserver/logger.go
index f8ec8b276..1fc262419 100644
--- a/caddyhttp/httpserver/logger.go
+++ b/caddyhttp/httpserver/logger.go
@@ -44,6 +44,7 @@ type Logger struct {
 	V4ipMask     net.IPMask
 	V6ipMask     net.IPMask
 	IPMaskExists bool
+	Exceptions   []string
 }
 
 // NewTestLogger creates logger suitable for testing purposes
@@ -84,6 +85,17 @@ func (l Logger) MaskIP(ip string) string {
 
 }
 
+// ShouldLog returns true if the path is not exempted from
+// being logged (i.e. it is not found in l.Exceptions).
+func (l Logger) ShouldLog(path string) bool {
+	for _, exc := range l.Exceptions {
+		if Path(path).Matches(exc) {
+			return false
+		}
+	}
+	return true
+}
+
 // Attach binds logger Start and Close functions to
 // controller's OnStartup and OnShutdown hooks.
 func (l *Logger) Attach(controller *caddy.Controller) {
diff --git a/caddyhttp/log/log.go b/caddyhttp/log/log.go
index 251334fa9..251f091ca 100644
--- a/caddyhttp/log/log.go
+++ b/caddyhttp/log/log.go
@@ -67,6 +67,10 @@ func (l Logger) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error) {
 
 			// Write log entries
 			for _, e := range rule.Entries {
+				// Check if there is an exception to prevent log being written
+				if !e.Log.ShouldLog(r.URL.Path) {
+					continue
+				}
 
 				// Mask IP Address
 				if e.Log.IPMaskExists {
@@ -78,6 +82,7 @@ func (l Logger) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error) {
 					}
 				}
 				e.Log.Println(rep.Replace(e.Format))
+
 			}
 
 			return status, err
diff --git a/caddyhttp/log/log_test.go b/caddyhttp/log/log_test.go
index b804dcc3b..0b1329be8 100644
--- a/caddyhttp/log/log_test.go
+++ b/caddyhttp/log/log_test.go
@@ -177,3 +177,85 @@ func TestMultiEntries(t *testing.T) {
 		t.Errorf("Expected %q, but got %q", expect, got)
 	}
 }
+
+func TestLogExcept(t *testing.T) {
+	tests := []struct {
+		LogRules  []Rule
+		logPath   string
+		shouldLog bool
+	}{
+		{[]Rule{{
+			PathScope: "/",
+			Entries: []*Entry{{
+				Log: &httpserver.Logger{
+
+					Exceptions: []string{"/soup"},
+				},
+				Format: DefaultLogFormat,
+			}},
+		}}, `/soup`, false},
+		{[]Rule{{
+			PathScope: "/",
+			Entries: []*Entry{{
+				Log: &httpserver.Logger{
+
+					Exceptions: []string{"/tart"},
+				},
+				Format: DefaultLogFormat,
+			}},
+		}}, `/soup`, true},
+		{[]Rule{{
+			PathScope: "/",
+			Entries: []*Entry{{
+				Log: &httpserver.Logger{
+
+					Exceptions: []string{"/soup"},
+				},
+				Format: DefaultLogFormat,
+			}},
+		}}, `/tomatosoup`, true},
+		{[]Rule{{
+			PathScope: "/",
+			Entries: []*Entry{{
+				Log: &httpserver.Logger{
+
+					Exceptions: []string{"/pie/"},
+				},
+				Format: DefaultLogFormat,
+			}},
+			// Check exception with a trailing slash does not match without
+		}}, `/pie`, true},
+		{[]Rule{{
+			PathScope: "/",
+			Entries: []*Entry{{
+				Log: &httpserver.Logger{
+
+					Exceptions: []string{"/pie.php"},
+				},
+				Format: DefaultLogFormat,
+			}},
+		}}, `/pie`, true},
+		{[]Rule{{
+			PathScope: "/",
+			Entries: []*Entry{{
+				Log: &httpserver.Logger{
+
+					Exceptions: []string{"/pie"},
+				},
+				Format: DefaultLogFormat,
+			}},
+			// Check that a word without trailing slash will match a filename
+		}}, `/pie.php`, false},
+	}
+	for i, test := range tests {
+		for _, LogRule := range test.LogRules {
+			for _, e := range LogRule.Entries {
+				shouldLog := e.Log.ShouldLog(test.logPath)
+				if shouldLog != test.shouldLog {
+					t.Fatalf("Test  %d expected shouldLog=%t but got shouldLog=%t,", i, test.shouldLog, shouldLog)
+				}
+			}
+		}
+
+	}
+}
diff --git a/caddyhttp/log/setup.go b/caddyhttp/log/setup.go
index 64f2f77ca..0c889a9f7 100644
--- a/caddyhttp/log/setup.go
+++ b/caddyhttp/log/setup.go
@@ -44,7 +44,7 @@ func setup(c *caddy.Controller) error {
 
 func logParse(c *caddy.Controller) ([]*Rule, error) {
 	var rules []*Rule
-
+	var logExceptions []string
 	for c.Next() {
 		args := c.RemainingArgs()
 
@@ -91,6 +91,12 @@ func logParse(c *caddy.Controller) ([]*Rule, error) {
 
 				}
 
+			} else if what == "except" {
+
+				for i := 0; i < len(where); i++ {
+					logExceptions = append(logExceptions, where[i])
+				}
+
 			} else if httpserver.IsLogRollerSubdirective(what) {
 
 				if err := httpserver.ParseRoller(logRoller, what, where...); err != nil {
@@ -133,6 +139,7 @@ func logParse(c *caddy.Controller) ([]*Rule, error) {
 				V4ipMask:     ip4Mask,
 				V6ipMask:     ip6Mask,
 				IPMaskExists: ipMaskExists,
+				Exceptions:   logExceptions,
 			},
 			Format: format,
 		})