feat(core): rename ProbabilitySampler to TraceIdRatioBasedSampler (#1562

)

* feat(core): rename ProbabilitySampler to TraceIdRatioBasedSampler

TraceIdRatioBasedSamplers are determinist samplers based on trace ids.

* fixup!: rename ProbabilitySampler to TraceIdRatioBasedSampler

* fixup!: explicitly set spanContexts in tests

packages/opentelemetry-core/README.md

@@ -114,10 +114,10 @@ Samples a configurable percentage of traces, and additionally samples any trace
 
 ```js
 const { NodeTracerProvider } = require("@opentelemetry/node");
-const { ProbabilitySampler } = require("@opentelemetry/core");
+const { TraceIdRatioBasedSampler } = require("@opentelemetry/core");
 
 const tracerProvider = new NodeTracerProvider({
-  sampler: new ProbabilitySampler(0.5)
+  sampler: new TraceIdRatioBasedSampler(0.5)
 });
 ```
 

packages/opentelemetry-core/src/index.ts

@@ -32,7 +32,7 @@ export * from './trace/NoRecordingSpan';
 export * from './trace/sampler/AlwaysOffSampler';
 export * from './trace/sampler/AlwaysOnSampler';
 export * from './trace/sampler/ParentOrElseSampler';
-export * from './trace/sampler/ProbabilitySampler';
+export * from './trace/sampler/TraceIdRatioBasedSampler';
 export * from './trace/TraceState';
 export * from './trace/IdGenerator';
 export * from './utils/deep-merge';

packages/opentelemetry-core/src/trace/sampler/TraceIdRatioBasedSampler.ts

@@ -0,0 +1,55 @@
+/*
+ * 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.
+ */
+
+import {
+  Sampler,
+  SamplingDecision,
+  SamplingResult,
+  SpanContext,
+} from '@opentelemetry/api';
+
+/** Sampler that samples a given fraction of traces based of trace id deterministically. */
+export class TraceIdRatioBasedSampler implements Sampler {
+  constructor(private readonly _ratio: number = 0) {
+    this._ratio = this._normalize(_ratio);
+  }
+
+  shouldSample(
+    parentContext: SpanContext | undefined,
+    traceId: string
+  ): SamplingResult {
+    let accumulation = 0;
+    for (let idx = 0; idx < traceId.length; idx++) {
+      accumulation += traceId.charCodeAt(idx);
+    }
+    const cmp = (accumulation % 100) / 100;
+    return {
+      decision:
+        cmp < this._ratio
+          ? SamplingDecision.RECORD_AND_SAMPLED
+          : SamplingDecision.NOT_RECORD,
+    };
+  }
+
+  toString(): string {
+    return `TraceIdRatioBased{${this._ratio}}`;
+  }
+
+  private _normalize(ratio: number): number {
+    if (typeof ratio !== 'number' || isNaN(ratio)) return 0;
+    return ratio >= 1 ? 1 : ratio <= 0 ? 0 : ratio;
+  }
+}

packages/opentelemetry-core/test/trace/ParentOrElseSampler.test.ts

@@ -19,7 +19,7 @@ import { AlwaysOnSampler } from '../../src/trace/sampler/AlwaysOnSampler';
 import { ParentOrElseSampler } from '../../src/trace/sampler/ParentOrElseSampler';
 import { TraceFlags, SpanKind } from '@opentelemetry/api';
 import { AlwaysOffSampler } from '../../src/trace/sampler/AlwaysOffSampler';
-import { ProbabilitySampler } from '../../src';
+import { TraceIdRatioBasedSampler } from '../../src';
 
 const traceId = 'd4cda95b652f4a1592b449d5929fda1b';
 const spanId = '6e0c63257de34c92';
@@ -33,10 +33,10 @@ describe('ParentOrElseSampler', () => {
     sampler = new ParentOrElseSampler(new AlwaysOnSampler());
     assert.strictEqual(sampler.toString(), 'ParentOrElse{AlwaysOnSampler}');
 
-    sampler = new ParentOrElseSampler(new ProbabilitySampler(0.5));
+    sampler = new ParentOrElseSampler(new TraceIdRatioBasedSampler(0.5));
     assert.strictEqual(
       sampler.toString(),
-      'ParentOrElse{ProbabilitySampler{0.5}}'
+      'ParentOrElse{TraceIdRatioBased{0.5}}'
     );
   });