Precompile log buffer regular expressions

Compile fixed patterns during monitor and log counter initialization, pass compiled expressions to the log buffer, and reject invalid log counter patterns before watching logs.

pkg/systemlogmonitor/log_monitor.go

@@ -20,6 +20,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"regexp"
 	"time"
 
 	"k8s.io/klog/v2"
@@ -50,6 +51,7 @@ type logMonitor struct {
 	watcher    watchertypes.LogWatcher
 	buffer     LogBuffer
 	config     MonitorConfig
+	patterns   []*regexp.Regexp
 	conditions []types.Condition
 	logCh      <-chan *systemlogtypes.Log
 	output     chan *types.Status
@@ -73,7 +75,7 @@ func NewLogMonitorOrDie(configPath string) types.Monitor {
 	}
 	// Apply default configurations
 	(&l.config).ApplyDefaultConfiguration()
-	err = l.config.ValidateRules()
+	l.patterns, err = l.config.compileRules()
 	if err != nil {
 		klog.Fatalf("Failed to validate %s matching rules %+v: %v", l.configPath, l.config.Rules, err)
 	}
@@ -152,8 +154,8 @@ func (l *logMonitor) parseLog(log *systemlogtypes.Log) {
 	// Once there is new log, log monitor will push it into the log buffer and try
 	// to match each rule. If any rule is matched, log monitor will report a status.
 	l.buffer.Push(log)
-	for _, rule := range l.config.Rules {
-		matched := l.buffer.Match(rule.Pattern)
+	for i, rule := range l.config.Rules {
+		matched := l.buffer.Match(l.patterns[i])
 		if len(matched) == 0 {
 			continue
 		}