refactor: extract OTEL_TRACES_SAMPLER values to enum

packages/opentelemetry-core/src/index.ts

@@ -34,3 +34,4 @@ export * from './trace/TraceState';
 export * from './trace/IdGenerator';
 export * from './utils/url';
 export * from './utils/wrap';
+export * from './utils/sampling';

packages/opentelemetry-core/src/utils/environment.ts

@@ -15,6 +15,7 @@
  */
 
 import { DiagLogLevel } from '@opentelemetry/api';
+import { TracesSamplerValues } from './sampling';
 
 const DEFAULT_LIST_SEPARATOR = ',';
 
@@ -104,8 +105,8 @@ export const DEFAULT_ENVIRONMENT: Required<ENVIRONMENT> = {
   OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT: 128,
   OTEL_SPAN_EVENT_COUNT_LIMIT: 128,
   OTEL_SPAN_LINK_COUNT_LIMIT: 128,
+  OTEL_TRACES_SAMPLER: TracesSamplerValues.ParentBasedAlwaysOn,
   OTEL_TRACES_SAMPLER_ARG: '',
-  OTEL_TRACES_SAMPLER: 'parentbased_always_on',
 };
 
 /**

packages/opentelemetry-core/src/utils/sampling.ts

@@ -0,0 +1,24 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+export enum TracesSamplerValues {
+  AlwaysOff = 'always_off',
+  AlwaysOn = 'always_on',
+  ParentBasedAlwaysOff = 'parentbased_always_off',
+  ParentBasedAlwaysOn = 'parentbased_always_on',
+  ParentBasedTraceIdRatio = 'parentbased_traceidratio',
+  TraceIdRatio = 'traceidratio',
+}

packages/opentelemetry-core/test/utils/environment.test.ts

@@ -23,6 +23,7 @@ import {
 import * as assert from 'assert';
 import * as sinon from 'sinon';
 import { DiagLogLevel } from '@opentelemetry/api';
+import { TracesSamplerValues } from '../../src';
 
 let lastMock: RAW_ENVIRONMENT = {};
 
@@ -146,12 +147,15 @@ describe('environment', () => {
     it('should remove a mock environment', () => {
       mockEnvironment({
         OTEL_LOG_LEVEL: 'DEBUG',
-        OTEL_TRACES_SAMPLER: 'always_off',
+        OTEL_TRACES_SAMPLER: TracesSamplerValues.AlwaysOff,
       });
       removeMockEnvironment();
       const env = getEnv();
       assert.strictEqual(env.OTEL_LOG_LEVEL, DiagLogLevel.INFO);
-      assert.strictEqual(env.OTEL_TRACES_SAMPLER, 'parentbased_always_on');
+      assert.strictEqual(
+        env.OTEL_TRACES_SAMPLER,
+        TracesSamplerValues.ParentBasedAlwaysOn
+      );
     });
   });
 });

packages/opentelemetry-tracing/src/config.ts

@@ -19,6 +19,7 @@ import {
   AlwaysOffSampler,
   AlwaysOnSampler,
   getEnv,
+  TracesSamplerValues,
   ParentBasedSampler,
   TraceIdRatioBasedSampler,
 } from '@opentelemetry/core';
@@ -41,6 +42,8 @@ export const DEFAULT_CONFIG = {
   },
 };
 
+const FALLBACK_OTEL_TRACES_SAMPLER = TracesSamplerValues.AlwaysOn;
+
 /**
  * Based on environment, builds a sampler, complies with specification.
  * @param env optional, by default uses getEnv(), but allows passing a value to reuse parsed environment
@@ -49,27 +52,27 @@ export function buildSamplerFromEnv(
   env: Required<ENVIRONMENT> = getEnv()
 ): Sampler {
   switch (env.OTEL_TRACES_SAMPLER) {
-    case 'always_on':
+    case TracesSamplerValues.AlwaysOn:
       return new AlwaysOnSampler();
-    case 'always_off':
+    case TracesSamplerValues.AlwaysOff:
       return new AlwaysOffSampler();
-    case 'parentbased_always_on':
+    case TracesSamplerValues.ParentBasedAlwaysOn:
       return new ParentBasedSampler({
         root: new AlwaysOnSampler(),
       });
-    case 'parentbased_always_off':
+    case TracesSamplerValues.ParentBasedAlwaysOff:
       return new ParentBasedSampler({
         root: new AlwaysOffSampler(),
       });
-    case 'traceidratio':
+    case TracesSamplerValues.TraceIdRatio:
       return new TraceIdRatioBasedSampler(getSamplerProbabilityFromEnv(env));
-    case 'parentbased_traceidratio':
+    case TracesSamplerValues.ParentBasedTraceIdRatio:
       return new ParentBasedSampler({
         root: new TraceIdRatioBasedSampler(getSamplerProbabilityFromEnv(env)),
       });
     default:
       diag.error(
-        `OTEL_TRACES_SAMPLER value "${env.OTEL_TRACES_SAMPLER} invalid, defaulting to always_on".`
+        `OTEL_TRACES_SAMPLER value "${env.OTEL_TRACES_SAMPLER} invalid, defaulting to ${FALLBACK_OTEL_TRACES_SAMPLER}".`
       );
       return new AlwaysOnSampler();
   }