fix(sdk-trace-base): don't load envs top level (#5233)

Author: lucacasonato

CHANGELOG.md

@@ -15,6 +15,8 @@ For semantic convention package changes, see the [semconv CHANGELOG](packages/se
 
 ### :bug: (Bug Fix)
 
+* fix(sdk-trace-base): do not load OTEL_ env vars on module load, but when needed [#5224](https://github.com/open-telemetry/opentelemetry-js/pull/5224)
+
 ### :books: (Refine Doc)
 
 ### :house: (Internal)

packages/opentelemetry-sdk-trace-base/src/config.ts

@@ -22,7 +22,6 @@ import { AlwaysOnSampler } from './sampler/AlwaysOnSampler';
 import { ParentBasedSampler } from './sampler/ParentBasedSampler';
 import { TraceIdRatioBasedSampler } from './sampler/TraceIdRatioBasedSampler';
 
-const env = getEnv();
 const FALLBACK_OTEL_TRACES_SAMPLER = TracesSamplerValues.AlwaysOn;
 const DEFAULT_RATIO = 1;
 
@@ -36,23 +35,23 @@ const DEFAULT_RATIO = 1;
 // object needs to be wrapped in this function and called when needed otherwise
 // envs are parsed before tests are ran - causes tests using these envs to fail
 export function loadDefaultConfig() {
-  const _env = getEnv();
+  const env = getEnv();
 
   return {
     sampler: buildSamplerFromEnv(env),
     forceFlushTimeoutMillis: 30000,
     generalLimits: {
-      attributeValueLengthLimit: _env.OTEL_ATTRIBUTE_VALUE_LENGTH_LIMIT,
-      attributeCountLimit: _env.OTEL_ATTRIBUTE_COUNT_LIMIT,
+      attributeValueLengthLimit: env.OTEL_ATTRIBUTE_VALUE_LENGTH_LIMIT,
+      attributeCountLimit: env.OTEL_ATTRIBUTE_COUNT_LIMIT,
     },
     spanLimits: {
-      attributeValueLengthLimit: _env.OTEL_SPAN_ATTRIBUTE_VALUE_LENGTH_LIMIT,
-      attributeCountLimit: _env.OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT,
-      linkCountLimit: _env.OTEL_SPAN_LINK_COUNT_LIMIT,
-      eventCountLimit: _env.OTEL_SPAN_EVENT_COUNT_LIMIT,
+      attributeValueLengthLimit: env.OTEL_SPAN_ATTRIBUTE_VALUE_LENGTH_LIMIT,
+      attributeCountLimit: env.OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT,
+      linkCountLimit: env.OTEL_SPAN_LINK_COUNT_LIMIT,
+      eventCountLimit: env.OTEL_SPAN_EVENT_COUNT_LIMIT,
       attributePerEventCountLimit:
-        _env.OTEL_SPAN_ATTRIBUTE_PER_EVENT_COUNT_LIMIT,
-      attributePerLinkCountLimit: _env.OTEL_SPAN_ATTRIBUTE_PER_LINK_COUNT_LIMIT,
+        env.OTEL_SPAN_ATTRIBUTE_PER_EVENT_COUNT_LIMIT,
+      attributePerLinkCountLimit: env.OTEL_SPAN_ATTRIBUTE_PER_LINK_COUNT_LIMIT,
     },
     mergeResourceWithDefaults: true,
   };