feat: Modify end time of lambda load span to be last cold start node … (#372)

* feat: Modify end time of lambda load span to be last cold start node end time instead of start time of function.

* fix: lint

* feat: Refactor to use the minimum of the beginning of the wrapped current span, or the end of the last cold start node

Author: astuyve

src/trace/cold-start-tracer.spec.ts

@@ -69,7 +69,7 @@ describe("ColdStartTracer", () => {
         name: "my-lambda-span",
       } as any as SpanWrapper,
       lambdaFunctionName: "my-function-name",
-      coldStartSpanFinishTime: 500,
+      currentSpanStartTime: 500,
       minDuration: 1,
       ignoreLibs: "",
     };
@@ -159,7 +159,7 @@ describe("ColdStartTracer", () => {
         name: "my-lambda-span",
       } as any as SpanWrapper,
       lambdaFunctionName: "my-function-name",
-      coldStartSpanFinishTime: 500,
+      currentSpanStartTime: 500,
       minDuration: 1,
       ignoreLibs: "myChildModule,myCoreModule",
     };

src/trace/cold-start-tracer.ts

@@ -6,7 +6,7 @@ export interface ColdStartTracerConfig {
   tracerWrapper: TracerWrapper;
   parentSpan?: SpanWrapper;
   lambdaFunctionName?: string;
-  coldStartSpanFinishTime: number; // Equivalent to the Lambda Span Start Time
+  currentSpanStartTime: number;
   minDuration: number;
   ignoreLibs: string;
 }
@@ -15,28 +15,29 @@ export class ColdStartTracer {
   private tracerWrapper: TracerWrapper;
   private parentSpan?: SpanWrapper;
   private lambdaFunctionName?: string;
-  private coldStartSpanFinishTime: number;
+  private currentSpanStartTime: number;
   private minDuration: number;
   private ignoreLibs: string[];
 
   constructor(coldStartTracerConfig: ColdStartTracerConfig) {
     this.tracerWrapper = coldStartTracerConfig.tracerWrapper;
     this.parentSpan = coldStartTracerConfig.parentSpan;
     this.lambdaFunctionName = coldStartTracerConfig.lambdaFunctionName;
-    this.coldStartSpanFinishTime = coldStartTracerConfig.coldStartSpanFinishTime;
+    this.currentSpanStartTime = coldStartTracerConfig.currentSpanStartTime;
     this.minDuration = coldStartTracerConfig.minDuration;
     this.ignoreLibs = coldStartTracerConfig.ignoreLibs.split(",");
   }
 
   trace(rootNodes: RequireNode[]) {
     const coldStartSpanStartTime = rootNodes[0]?.startTime;
-    const coldStartSpan = this.createColdStartSpan(coldStartSpanStartTime, this.parentSpan);
+    const coldStartSpanEndTime = Math.min(rootNodes[rootNodes.length - 1]?.endTime, this.currentSpanStartTime);
+    const coldStartSpan = this.createColdStartSpan(coldStartSpanStartTime, coldStartSpanEndTime, this.parentSpan);
     for (const coldStartNode of rootNodes) {
       this.traceTree(coldStartNode, coldStartSpan);
     }
   }
 
-  private createColdStartSpan(startTime: number, parentSpan: SpanWrapper | undefined): SpanWrapper {
+  private createColdStartSpan(startTime: number, endTime: number, parentSpan: SpanWrapper | undefined): SpanWrapper {
     const options: SpanOptions = {
       tags: {
         service: "aws.lambda",
@@ -50,7 +51,7 @@ export class ColdStartTracer {
       options.childOf = parentSpan.span;
     }
     const newSpan = new SpanWrapper(this.tracerWrapper.startSpan("aws.lambda.load", options), {});
-    newSpan.finish(this.coldStartSpanFinishTime);
+    newSpan.finish(endTime);
     return newSpan;
   }
 

src/trace/listener.ts

@@ -160,9 +160,9 @@ export class TraceListener {
     if (coldStartNodes.length > 0 && didFunctionColdStart()) {
       const coldStartConfig: ColdStartTracerConfig = {
         tracerWrapper: this.tracerWrapper,
-        coldStartSpanFinishTime: this.wrappedCurrentSpan?.startTime(),
         parentSpan: this.inferredSpan || this.wrappedCurrentSpan,
         lambdaFunctionName: this.context?.functionName,
+        currentSpanStartTime: this.wrappedCurrentSpan?.startTime(),
         minDuration: this.config.minColdStartTraceDuration,
         ignoreLibs: this.config.coldStartTraceSkipLib,
       };