UDPExporter should be useable when Application Signals is disabled on Lambda (#148)

*Issue #, if available:*
Currently, if AppSignals is disabled, UDP Span Exporter not usable in
Lambda.

[According to this
comment](https://github.com/aws-observability/aws-otel-js-instrumentation/blob/v0.5.0/aws-distro-opentelemetry-node-autoinstrumentation/src/aws-opentelemetry-configurator.ts#L440-L443),
the correct logic should be:

>If isLambdaEnvironment is true, we will default to exporting OTel spans
via udp_exporter, regardless of whether AppSignals is true or false.

Currently, this is not respected because when AppSignals is disabled,
ADOT's otel config cannot use the UDPExporter
- Currently, the only difference between the `AppSignals enabled` and
`AppSignals disabled` configurations is that in the "disabled" case,
ADOT leaves the Span Exporter/Processor and textMapPropagator
initialization work to the OTel JS SDK. Only in `AppSignals enabled`
scenario, the configured UDPExporter is accessible.

*Description of changes:*
Update `configure()` to not depend on AppSignalsEnabled flag (always use
the Span Exporter/Processor and textMapPropagator configurations made
from the ADOT configurator)
- [Similarly to
Python](https://github.com/aws-observability/aws-otel-python-instrumentation/blob/v0.8.0/aws-opentelemetry-distro/src/amazon/opentelemetry/distro/aws_opentelemetry_configurator.py#L181),
always use the ADOT configured Span Exporter/Processor, which is already
configured based on the AppSignalsEnabled flag
- textMapPropagator configuration is still using [upstream's
configuration](https://github.com/aws-observability/aws-otel-js-instrumentation/blob/v0.5.0/aws-distro-opentelemetry-node-autoinstrumentation/src/aws-opentelemetry-configurator.ts#L163)
(includes the XRay Propagator)

*Testing:*
- Add Unit Test
- Test that spans are exported in Lambda when AppSignals is disabled

By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice.

Author: jj22ee

aws-distro-opentelemetry-node-autoinstrumentation/src/aws-opentelemetry-configurator.ts

@@ -188,35 +188,23 @@ export class AwsOpentelemetryConfigurator {
   }
 
   public configure(): Partial<NodeSDKConfiguration> {
-    let config: Partial<NodeSDKConfiguration>;
-    if (AwsOpentelemetryConfigurator.isApplicationSignalsEnabled()) {
-      // config.autoDetectResources is set to False, as the resources are detected and added to the
-      // resource ahead of time. The resource is needed to be populated ahead of time instead of letting
-      // the OTel Node SDK do the population work because the constructed resource was required to build
-      // the sampler (if using XRay sampler) and the AwsMetricAttributesSpanExporter and AwsSpanMetricsProcessor
-      config = {
-        instrumentations: this.instrumentations,
-        resource: this.resource,
-        idGenerator: this.idGenerator,
-        sampler: this.sampler,
-        // Error message 'Exporter "otlp" requested through environment variable is unavailable.'
-        // will appear from BasicTracerProvider that is used in the OTel JS SDK, even though the
-        // span processors are specified
-        // https://github.com/open-telemetry/opentelemetry-js/issues/3449
-        spanProcessors: this.spanProcessors,
-        autoDetectResources: false,
-        textMapPropagator: this.propagator,
-      };
-    } else {
-      // Default experience config
-      config = {
-        instrumentations: this.instrumentations,
-        resource: this.resource,
-        sampler: this.sampler,
-        idGenerator: this.idGenerator,
-        autoDetectResources: false,
-      };
-    }
+    // config.autoDetectResources is set to False, as the resources are detected and added to the
+    // resource ahead of time. The resource is needed to be populated ahead of time instead of letting
+    // the OTel Node SDK do the population work because the constructed resource was required to build
+    // the sampler (if using XRay sampler) and the AwsMetricAttributesSpanExporter and AwsSpanMetricsProcessor
+    const config: Partial<NodeSDKConfiguration> = {
+      instrumentations: this.instrumentations,
+      resource: this.resource,
+      idGenerator: this.idGenerator,
+      sampler: this.sampler,
+      // Error message 'Exporter "otlp" requested through environment variable is unavailable.'
+      // will appear from BasicTracerProvider that is used in the OTel JS SDK, even though the
+      // span processors are specified
+      // https://github.com/open-telemetry/opentelemetry-js/issues/3449
+      spanProcessors: this.spanProcessors,
+      autoDetectResources: false,
+      textMapPropagator: this.propagator,
+    };
 
     return config;
   }

aws-distro-opentelemetry-node-autoinstrumentation/test/aws-opentelemetry-configurator.test.ts

@@ -9,7 +9,13 @@ import { OTLPTraceExporter as OTLPHttpTraceExporter } from '@opentelemetry/expor
 import { OTLPTraceExporter as OTLPProtoTraceExporter } from '@opentelemetry/exporter-trace-otlp-proto';
 import { Resource } from '@opentelemetry/resources';
 import { PushMetricExporter } from '@opentelemetry/sdk-metrics';
-import { AlwaysOffSampler, ReadableSpan, SpanProcessor, TraceIdRatioBasedSampler } from '@opentelemetry/sdk-trace-base';
+import {
+  AlwaysOffSampler,
+  BatchSpanProcessor,
+  ReadableSpan,
+  SpanProcessor,
+  TraceIdRatioBasedSampler,
+} from '@opentelemetry/sdk-trace-base';
 import {
   AlwaysOnSampler,
   NodeTracerProvider,
@@ -457,6 +463,24 @@ describe('AwsOpenTelemetryConfiguratorTest', () => {
     delete process.env.AWS_XRAY_DAEMON_ADDRESS;
   });
 
+  it('Tests that OTLP exporter from the configurator is UDPExporter when Application Signals is disabled on Lambda', () => {
+    process.env.AWS_LAMBDA_FUNCTION_NAME = 'TestFunction';
+    process.env.OTEL_AWS_APPLICATION_SIGNALS_ENABLED = 'False';
+    process.env.OTEL_TRACES_EXPORTER = 'otlp';
+    process.env.AWS_XRAY_DAEMON_ADDRESS = 'www.test.com:2222';
+
+    const config = new AwsOpentelemetryConfigurator([]).configure();
+    expect((config.spanProcessors as any)[0]).toBeInstanceOf(BatchSpanProcessor);
+    expect((config.spanProcessors as any)[0]._exporter).toBeInstanceOf(OTLPUdpSpanExporter);
+    expect((config.spanProcessors as any)[0]._exporter._endpoint).toBe('www.test.com:2222');
+    expect(config.spanProcessors?.length).toEqual(1);
+
+    delete process.env.AWS_LAMBDA_FUNCTION_NAME;
+    delete process.env.OTEL_AWS_APPLICATION_SIGNALS_ENABLED;
+    delete process.env.OTEL_TRACES_EXPORTER;
+    delete process.env.AWS_XRAY_DAEMON_ADDRESS;
+  });
+
   it('Test CustomizeSpanProcessors for Lambda', () => {
     process.env.OTEL_AWS_APPLICATION_SIGNALS_ENABLED = 'True';
     process.env.AWS_LAMBDA_FUNCTION_NAME = 'TestFunction';