From e83c0aeb34aafe35ad9b9ede8b7b26e4c8444c20 Mon Sep 17 00:00:00 2001
From: Jamie Danielson <jamiedanielson@honeycomb.io>
Date: Wed, 17 Jul 2024 17:07:48 -0400
Subject: [PATCH] update to more reliable test and update docs

---
 metapackages/auto-instrumentations-node/README.md     |  3 +++
 metapackages/auto-instrumentations-node/src/utils.ts  |  2 +-
 .../auto-instrumentations-node/test/utils.test.ts     | 11 +++++++----
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/metapackages/auto-instrumentations-node/README.md b/metapackages/auto-instrumentations-node/README.md
index c32df7c437..2c324438de 100644
--- a/metapackages/auto-instrumentations-node/README.md
+++ b/metapackages/auto-instrumentations-node/README.md
@@ -97,6 +97,9 @@ To disable only [@opentelemetry/instrumentation-fs](https://github.com/open-tele
 export OTEL_NODE_DISABLED_INSTRUMENTATIONS="fs"
 ```
 
+If both environment variables are set, `OTEL_NODE_ENABLED_INSTRUMENTATIONS` is applied first, and then `OTEL_NODE_DISABLED_INSTRUMENTATIONS` is applied to that list.
+Therefore, if the same instrumentation is included in both lists, that instrumentation will be disabled.
+
 To enable logging for troubleshooting, set the log level by setting the `OTEL_LOG_LEVEL` environment variable to one of the following:
 
 - `none`
diff --git a/metapackages/auto-instrumentations-node/src/utils.ts b/metapackages/auto-instrumentations-node/src/utils.ts
index ac8bd4b60d..a9e2b0755f 100644
--- a/metapackages/auto-instrumentations-node/src/utils.ts
+++ b/metapackages/auto-instrumentations-node/src/utils.ts
@@ -151,7 +151,7 @@ export function getNodeAutoInstrumentations(
 
   if (enabledInstrumentationsFromEnv && disabledInstrumentationsFromEnv) {
     diag.debug(
-      'OTEL_NODE_ENABLED_INSTRUMENTATIONS and OTEL_NODE_DISABLED_INSTRUMENTATIONS environment variables are mutually exclusive. All instrumentations are disabled.'
+      'OTEL_NODE_ENABLED_INSTRUMENTATIONS and OTEL_NODE_DISABLED_INSTRUMENTATIONS are both set.\nAny instrumentation that exists in both lists will be disabled.'
     );
   }
 
diff --git a/metapackages/auto-instrumentations-node/test/utils.test.ts b/metapackages/auto-instrumentations-node/test/utils.test.ts
index 6a6a9b22e2..cc7cb24c68 100644
--- a/metapackages/auto-instrumentations-node/test/utils.test.ts
+++ b/metapackages/auto-instrumentations-node/test/utils.test.ts
@@ -114,15 +114,18 @@ describe('utils', () => {
       }
     });
 
-    it('will disable all instrumentations if both OTEL_NODE_ENABLED_INSTRUMENTATIONS and OTEL_NODE_DISABLED_INSTRUMENTATIONS are set', () => {
-      process.env.OTEL_NODE_DISABLED_INSTRUMENTATIONS = 'fs';
-      process.env.OTEL_NODE_ENABLED_INSTRUMENTATIONS = 'fs';
+    it('should disable any instrumentations from OTEL_NODE_ENABLED_INSTRUMENTATIONS if set in OTEL_NODE_DISABLED_INSTRUMENTATIONS', () => {
+      process.env.OTEL_NODE_ENABLED_INSTRUMENTATIONS = 'http,express,net';
+      process.env.OTEL_NODE_DISABLED_INSTRUMENTATIONS = 'fs,net'; // fs is no-op here, already disabled
       try {
         const instrumentations = getNodeAutoInstrumentations();
 
         assert.deepStrictEqual(
           new Set(instrumentations.map(i => i.instrumentationName)),
-          new Set()
+          new Set([
+            '@opentelemetry/instrumentation-http',
+            '@opentelemetry/instrumentation-express',
+          ])
         );
       } finally {
         delete process.env.OTEL_NODE_DISABLED_INSTRUMENTATIONS;