Merge pull request #1322 from DigitalVeer/logbuffer-regexp-cache

Cache compiled regular expressions in the log buffer

pkg/systemlogmonitor/log_buffer.go

@@ -39,6 +39,8 @@ type logBuffer struct {
 	msg     []string
 	max     int
 	current int
+	// regexps caches compiled regular expressions.
+	regexps map[string]*regexp.Regexp
 }
 
 // NewLogBuffer creates log buffer with max line number limit. Because we only match logs
@@ -47,9 +49,10 @@ type logBuffer struct {
 // lines of patterns we support.
 func NewLogBuffer(maxLines int) *logBuffer {
 	return &logBuffer{
-		buffer: make([]*types.Log, maxLines),
-		msg:    make([]string, maxLines),
-		max:    maxLines,
+		buffer:  make([]*types.Log, maxLines),
+		msg:     make([]string, maxLines),
+		max:     maxLines,
+		regexps: make(map[string]*regexp.Regexp),
 	}
 }
 
@@ -59,10 +62,13 @@ func (b *logBuffer) Push(log *types.Log) {
 	b.current++
 }
 
-// TODO(random-liu): Cache regexp if garbage collection becomes a problem someday.
 func (b *logBuffer) Match(expr string) []*types.Log {
 	// The expression should be checked outside, and it must match to the end.
-	reg := regexp.MustCompile(expr + `\z`)
+	reg, ok := b.regexps[expr]
+	if !ok {
+		reg = regexp.MustCompile(expr + `\z`)
+		b.regexps[expr] = reg
+	}
 	log := b.String()
 	loc := reg.FindStringIndex(log)
 	if loc == nil {

pkg/systemlogmonitor/log_buffer_test.go

@@ -108,3 +108,17 @@ func TestMatch(t *testing.T) {
 		}
 	}
 }
+
+func BenchmarkMatch(b *testing.B) {
+	buf := NewLogBuffer(10)
+	for i := 0; i < 10; i++ {
+		buf.Push(&types.Log{Message: "Out of memory: Kill process 20744 (mysqld) score 318 or sacrifice child"})
+	}
+	// A pattern from the default kernel monitor configuration which does not
+	// match the buffered logs.
+	expr := `task [\S ]+:\w+ blocked for more than \w+ seconds\.`
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		buf.Match(expr)
+	}
+}