chore: add debug logs for configs affecting Kibana UI (#737)

Co-authored-by: Trent Mick <[email protected]>

Author: david-luna

packages/opentelemetry-node/lib/detectors.js

@@ -97,6 +97,14 @@ function resolveDetectors(detectors) {
         return [];
     }
 
+    // NOTE: Kibana is doing a breakdown by service instance when plotting the metrics dashboard. So it needs the instance ID.
+    // Dashboard was added in https://github.com/elastic/kibana/pull/215735
+    if (!detectorKeys.includes('serviceinstance')) {
+        log.info(
+            `The "serviceinstance" resource detector has not been selected. This will result in Kibana's APM Service Metrics dashboard not working. See https://elastic.github.io/opentelemetry/edot-sdks/nodejs/configuration.html#otel_node_resource_detectors-details`
+        );
+    }
+
     /** @type {Array<ResourceDetector | ResourceDetector[]>} */
     const resolvedDetectors = [distroDetector];
     for (const key of detectorKeys) {

packages/opentelemetry-node/lib/environment.js

@@ -10,11 +10,6 @@ const envToRestore = {};
  * Tweak `process.env` before calling NodeSDK.
  */
 function setupEnvironment() {
-    if (!('OTEL_TRACES_EXPORTER' in process.env)) {
-        // Ensure this envvar is set to avoid a diag.warn() in NodeSDK.
-        process.env.OTEL_TRACES_EXPORTER = 'otlp';
-    }
-
     if ('OTEL_LOG_LEVEL' in process.env) {
         envToRestore['OTEL_LOG_LEVEL'] = process.env.OTEL_LOG_LEVEL;
         // Make sure NodeSDK doesn't see this envvar and overwrite our diag

packages/opentelemetry-node/lib/sdk.js

@@ -134,13 +134,20 @@ function startNodeSDK(cfg = {}) {
     // TODO: support `OTEL_METRICS_EXPORTER`, including being a list of exporters (e.g. console, debug)
     // TODO: metrics exporter should do for metrics what `TracerProviderWithEnvExporters` does for traces, does that include `url` export endpoint?
 
+    // Setting default temporality to delta to avoid histogram storing issues in ES.
+    // Or log if there is a different value set by the user
+    // Ref: https://github.com/elastic/opentelemetry/pull/63
     const temporalityPreference = getStringFromEnv(
         'OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE'
     );
     if (typeof temporalityPreference === 'undefined') {
-        // Setting default temporality to delta to avoid histogram storing issues in ES
-        // Ref: https://github.com/elastic/opentelemetry/pull/63
         process.env.OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE = 'delta';
+    } else if (temporalityPreference !== 'delta') {
+        const docsUrl =
+            'https://elastic.github.io/opentelemetry/compatibility/limitations.html#ingestion-of-metrics-data';
+        log.info(
+            `Metrics temporality preference set to "${temporalityPreference}". Use "delta" temporality if you want to store Histogram metrics in Elasticsearch. See ${docsUrl}`
+        );
     }
 
     // The implementation in SDK does treats the undefined and 'none' value