lint: fix nilaway warnings (part 2) (#3854)

Author: mmetc

pkg/parser/runtime.go

@@ -226,8 +226,13 @@ var (
 )
 
 var (
-	StageParseCache dumps.ParserResults
+	StageParseCache dumps.ParserResults = make(dumps.ParserResults)
 	StageParseMutex sync.Mutex
+	// initialize the cache only once, even if called concurrently
+	ensureStageCache = sync.OnceFunc(func() {
+		StageParseCache["success"] = make(map[string][]dumps.ParserResult)
+		StageParseCache["success"][""] = make([]dumps.ParserResult, 0)
+	})
 )
 
 func Parse(ctx UnixParserCtx, xp types.Event, nodes []Node) (types.Event, error) {
@@ -260,23 +265,10 @@ func Parse(ctx UnixParserCtx, xp types.Event, nodes []Node) (types.Event, error)
 	}
 
 	if ParseDump {
-		if StageParseCache == nil {
-			StageParseMutex.Lock()
-			StageParseCache = make(dumps.ParserResults)
-			StageParseCache["success"] = make(map[string][]dumps.ParserResult)
-			StageParseCache["success"][""] = make([]dumps.ParserResult, 0)
-			StageParseMutex.Unlock()
-		}
+		ensureStageCache()
 	}
 
 	for _, stage := range ctx.Stages {
-		if ParseDump {
-			StageParseMutex.Lock()
-			if _, ok := StageParseCache[stage]; !ok {
-				StageParseCache[stage] = make(map[string][]dumps.ParserResult)
-			}
-			StageParseMutex.Unlock()
-		}
 		/* if the node is forward in stages, seek to this stage */
 		/* this is for example used by testing system to inject logs in post-syslog-parsing phase*/
 		if stageidx(event.Stage, ctx.Stages) > stageidx(stage, ctx.Stages) {
@@ -314,19 +306,31 @@ func Parse(ctx UnixParserCtx, xp types.Event, nodes []Node) (types.Event, error)
 			clog.Tracef("node (%s) ret : %v", nodes[idx].rn, ret)
 			if ParseDump {
 				var parserIdxInStage int
+
+				// copy outside of critical section
+				evtcopy := deepcopy.Copy(event)
+				name := nodes[idx].Name
+
+				// ensure the stage map exists
 				StageParseMutex.Lock()
-				if len(StageParseCache[stage][nodes[idx].Name]) == 0 {
-					StageParseCache[stage][nodes[idx].Name] = make([]dumps.ParserResult, 0)
-					parserIdxInStage = len(StageParseCache[stage])
+				stageMap, ok := StageParseCache[stage]
+				if !ok {
+					stageMap = make(map[string][]dumps.ParserResult)
+					StageParseCache[stage] = stageMap
+				}
+
+				// ensure the slice for this parser exists
+				if _, ok := stageMap[name]; !ok {
+					stageMap[name] = make([]dumps.ParserResult, 0)
+					parserIdxInStage = len(stageMap)
 				} else {
-					parserIdxInStage = StageParseCache[stage][nodes[idx].Name][0].Idx
+					parserIdxInStage = stageMap[name][0].Idx
 				}
-				StageParseMutex.Unlock()
 
-				evtcopy := deepcopy.Copy(event)
-				parserInfo := dumps.ParserResult{Evt: evtcopy.(types.Event), Success: ret, Idx: parserIdxInStage}
-				StageParseMutex.Lock()
-				StageParseCache[stage][nodes[idx].Name] = append(StageParseCache[stage][nodes[idx].Name], parserInfo)
+				stageMap[name] = append(stageMap[name], dumps.ParserResult{
+					Evt: evtcopy.(types.Event),
+					Success: ret, Idx: parserIdxInStage,
+				})
 				StageParseMutex.Unlock()
 			}
 			if ret {