Warm up http/proto exporter by sending special spans (#56)

* Use http/proto exporter instead of grpc to reduce the cost of loading libraries

* Disable tracing/metrics of http exporter

* Warm up http/proto exporter by sending special spans

nodejs/packages/cx-wrapper/index.ts

@@ -10,25 +10,45 @@ import { load } from './loader.js';
 import { initializeInstrumentations } from './instrumentation-init.js';
 import { initializeProvider } from './provider-init.js';
 import { makeLambdaInstrumentation } from './lambda-instrumentation-init.js';
+import { parseBooleanEnvvar } from './common.js';
 
 const instrumentations = initializeInstrumentations();
-initializeProvider(instrumentations);
+const tracerProvider = initializeProvider(instrumentations);
 const lambdaInstrumentation = makeLambdaInstrumentation();
 
 if (process.env.CX_ORIGINAL_HANDLER === undefined)
   throw Error('CX_ORIGINAL_HANDLER is missing');
 
 // We want user code to get initialized during lambda init phase
-diag.debug(`Initialization: Loading original handler ${process.env.CX_ORIGINAL_HANDLER}`);
 try {
   (async () => {
+    diag.debug(`Initialization: Loading original handler ${process.env.CX_ORIGINAL_HANDLER}`);
     await load(
       process.env.LAMBDA_TASK_ROOT,
       process.env.CX_ORIGINAL_HANDLER
     );
+    diag.debug(`Initialization: Original handler loaded`);
   })();
 } catch (e) {}
 
+if (parseBooleanEnvvar("OTEL_WARM_UP_EXPORTER") ?? true) {
+  // We want exporter code to get initialized during lambda init phase
+  try {
+    (async () => {
+      try {
+        diag.debug(`Initialization: warming up exporter`);
+        const warmupSpan = tracerProvider.getTracer('cx-wrapper').startSpan('warmup');
+        warmupSpan.setAttribute('cx.internal.span.role', 'warmup');
+        warmupSpan.end();
+        await tracerProvider.forceFlush();
+        diag.debug(`Initialization: exporter warmed up`);
+      } catch (e) {
+        diag.error(`Initialization: exporter warmup failed: ${e}`);
+      }
+    })();
+  } catch (e) {}
+}
+
 export const handler = (event: any, context: Context, callback: Callback) => {
   diag.debug(`Loading original handler ${process.env.CX_ORIGINAL_HANDLER}`);
   load(

nodejs/packages/cx-wrapper/provider-init.ts

@@ -22,7 +22,7 @@ declare global {
 
 const DEFAULT_OTEL_EXPORT_TIMEOUT = 2000; // this is a localhost call, and we don't want to block the function for too long
 
-export function initializeProvider(instrumentations: any[]): void {
+export function initializeProvider(instrumentations: any[]): NodeTracerProvider {
   diag.debug('Initializing OpenTelemetry providers');
 
   const export_timeout = parseIntEnvvar("OTEL_EXPORT_TIMEOUT") ?? DEFAULT_OTEL_EXPORT_TIMEOUT;
@@ -106,4 +106,6 @@ export function initializeProvider(instrumentations: any[]): void {
     tracerProvider,
     meterProvider
   });
-}
+
+  return tracerProvider
+}