End tracing early in autobuild Action for improved performance and reliability

This lets us achieve some performance and reliability improvements for
workflows that run autobuild directly without specifying a build mode.

src/analyze.ts

@@ -402,13 +402,10 @@ export async function runFinalize(
     logger,
   );
 
-  // WARNING: This does not _really_ end tracing, as the tracer will restore its
-  // critical environment variables and it'll still be active for all processes
-  // launched from this build step.
-  // However, it will stop tracing for all steps past the codeql-action/analyze
-  // step.
-  // Delete variables as specified by the end-tracing script
-  await endTracingForCluster(codeql, config, features);
+  // If we didn't already end tracing in the autobuild Action, end it now.
+  if (process.env[EnvVar.AUTOBUILD_DID_COMPLETE_SUCCESSFULLY] !== "true") {
+    await endTracingForCluster(codeql, config, logger, features);
+  }
   return timings;
 }
 

src/autobuild-action.ts

@@ -21,6 +21,7 @@ import {
   sendStatusReport,
   ActionName,
 } from "./status-report";
+import { endTracingForCluster } from "./tracer-config";
 import {
   checkActionVersion,
   checkDiskUsage,
@@ -125,6 +126,10 @@ async function run() {
         await runAutobuild(config, language, features, logger);
       }
     }
+
+    // End tracing early to avoid tracing analyze. This improves the performance and reliability of
+    // the analyze step.
+    await endTracingForCluster(codeql, config, logger, features);
   } catch (unwrappedError) {
     const error = wrapError(unwrappedError);
     core.setFailed(

src/tracer-config.ts

@@ -5,6 +5,7 @@ import { type CodeQL } from "./codeql";
 import { type Config } from "./config-utils";
 import { Feature, FeatureEnablement } from "./feature-flags";
 import { isTracedLanguage } from "./languages";
+import { Logger } from "./logging";
 import { ToolsFeature } from "./tools-features";
 import { BuildMode } from "./util";
 
@@ -28,13 +29,27 @@ export async function shouldEnableIndirectTracing(
   );
 }
 
+/**
+ * Delete variables as specified by the end-tracing script
+ *
+ * WARNING: This does not _really_ end tracing, as the tracer will restore its
+ * critical environment variables and it'll still be active for all processes
+ * launched from this build step.
+ *
+ * However, it will stop tracing for all steps past the current build step.
+ */
 export async function endTracingForCluster(
   codeql: CodeQL,
   config: Config,
+  logger: Logger,
   features: FeatureEnablement,
 ): Promise<void> {
   if (!(await shouldEnableIndirectTracing(codeql, config, features))) return;
 
+  logger.info(
+    "Unsetting build tracing environment variables. Subsequent steps of this job will not be traced.",
+  );
+
   const envVariablesFile = path.resolve(
     config.dbLocation,
     "temp/tracingEnvironment/end-tracing.json",