feat(core): Create types and utilities for span links (#15375)

This is the base for adding span links to the SDK. Those types will be
used both our OTel and Core SDK.

packages/core/src/index.ts

@@ -76,6 +76,7 @@ export { handleCallbackErrors } from './utils/handleCallbackErrors';
 export { parameterize } from './utils/parameterize';
 export { addAutoIpAddressToSession, addAutoIpAddressToUser } from './utils/ipAddress';
 export {
+  convertSpanLinksForEnvelope,
   spanToTraceHeader,
   spanToJSON,
   spanIsSampled,

packages/core/src/tracing/sentryNonRecordingSpan.ts

@@ -69,24 +69,12 @@ export class SentryNonRecordingSpan implements Span {
     return this;
   }
 
-  /**
-   * This should generally not be used,
-   * but we need it for being compliant with the OTEL Span interface.
-   *
-   * @hidden
-   * @internal
-   */
+  /** @inheritDoc */
   public addLink(_link: unknown): this {
     return this;
   }
 
-  /**
-   * This should generally not be used,
-   * but we need it for being compliant with the OTEL Span interface.
-   *
-   * @hidden
-   * @internal
-   */
+  /** @inheritDoc */
   public addLinks(_links: unknown[]): this {
     return this;
   }

packages/core/src/tracing/sentrySpan.ts

@@ -109,24 +109,12 @@ export class SentrySpan implements Span {
     }
   }
 
-  /**
-   * This should generally not be used,
-   * but it is needed for being compliant with the OTEL Span interface.
-   *
-   * @hidden
-   * @internal
-   */
+  /** @inheritDoc */
   public addLink(_link: unknown): this {
     return this;
   }
 
-  /**
-   * This should generally not be used,
-   * but it is needed for being compliant with the OTEL Span interface.
-   *
-   * @hidden
-   * @internal
-   */
+  /** @inheritDoc */
   public addLinks(_links: unknown[]): this {
     return this;
   }

packages/core/src/types-hoist/link.ts

@@ -0,0 +1,30 @@
+import type { SpanAttributeValue, SpanContextData } from './span';
+
+type SpanLinkAttributes = {
+  /**
+   * Setting the link type to 'previous_trace' helps the Sentry product linking to the previous trace
+   */
+  'sentry.link.type'?: string | 'previous_trace';
+} & Record<string, SpanAttributeValue | undefined>;
+
+export interface SpanLink {
+  /**
+   * Contains the SpanContext of the span to link to
+   */
+  context: SpanContextData;
+  /**
+   * A key-value pair with primitive values or an array of primitive values
+   */
+  attributes?: SpanLinkAttributes;
+}
+
+/**
+ * Link interface for the event envelope item. It's a flattened representation of `SpanLink`.
+ * Can include additional fields defined by OTel.
+ */
+export interface SpanLinkJSON extends Record<string, unknown> {
+  span_id: string;
+  trace_id: string;
+  sampled?: boolean;
+  attributes?: SpanLinkAttributes;
+}

packages/core/src/types-hoist/span.ts

@@ -1,3 +1,4 @@
+import type { SpanLink, SpanLinkJSON } from './link';
 import type { Measurements } from './measurement';
 import type { HrTime } from './opentelemetry';
 import type { SpanStatus } from './spanStatus';
@@ -50,6 +51,7 @@ export interface SpanJSON {
   measurements?: Measurements;
   is_segment?: boolean;
   segment_id?: string;
+  links?: SpanLinkJSON[];
 }
 
 // These are aligned with OpenTelemetry trace flags
@@ -249,14 +251,21 @@ export interface Span {
   addEvent(name: string, attributesOrStartTime?: SpanAttributes | SpanTimeInput, startTime?: SpanTimeInput): this;
 
   /**
-   * NOT USED IN SENTRY, only added for compliance with OTEL Span interface
+   * Associates this span with a related span. Links can reference spans from the same or different trace
+   * and are typically used for batch operations, cross-trace scenarios, or scatter/gather patterns.
+   *
+   * Prefer setting links directly when starting a span (e.g. `Sentry.startSpan()`) as some context information is only available during span creation.
+   * @param link - The link containing the context of the span to link to and optional attributes
    */
-  addLink(link: unknown): this;
+  addLink(link: SpanLink): this;
 
   /**
-   * NOT USED IN SENTRY, only added for compliance with OTEL Span interface
+   * Associates this span with multiple related spans. See {@link addLink} for more details.
+   *
+   * Prefer setting links directly when starting a span (e.g. `Sentry.startSpan()`) as some context information is only available during span creation.
+   * @param links - Array of links to associate with this span
    */
-  addLinks(links: unknown): this;
+  addLinks(links: SpanLink[]): this;
 
   /**
    * NOT USED IN SENTRY, only added for compliance with OTEL Span interface

packages/core/src/utils/spanUtils.ts

@@ -19,6 +19,7 @@ import type {
   SpanTimeInput,
   TraceContext,
 } from '../types-hoist';
+import type { SpanLink, SpanLinkJSON } from '../types-hoist/link';
 import { consoleSandbox } from '../utils-hoist/logger';
 import { addNonEnumerableProperty, dropUndefinedKeys } from '../utils-hoist/object';
 import { generateSpanId } from '../utils-hoist/propagationContext';
@@ -81,6 +82,25 @@ export function spanToTraceHeader(span: Span): string {
   return generateSentryTraceHeader(traceId, spanId, sampled);
 }
 
+/**
+ *  Converts the span links array to a flattened version to be sent within an envelope.
+ *
+ *  If the links array is empty, it returns `undefined` so the empty value can be dropped before it's sent.
+ */
+export function convertSpanLinksForEnvelope(links?: SpanLink[]): SpanLinkJSON[] | undefined {
+  if (links && links.length > 0) {
+    return links.map(({ context: { spanId, traceId, traceFlags, ...restContext }, attributes }) => ({
+      span_id: spanId,
+      trace_id: traceId,
+      sampled: traceFlags === TRACE_FLAG_SAMPLED,
+      attributes,
+      ...restContext,
+    }));
+  } else {
+    return undefined;
+  }
+}
+
 /**
  * Convert a span time input into a timestamp in seconds.
  */

packages/core/test/lib/utils/spanUtils.test.ts

@@ -7,14 +7,17 @@ import {
   SPAN_STATUS_UNSET,
   SentrySpan,
   TRACEPARENT_REGEXP,
+  convertSpanLinksForEnvelope,
   setCurrentClient,
   spanToTraceHeader,
   startInactiveSpan,
   startSpan,
   timestampInSeconds,
 } from '../../../src';
 import type { Span, SpanAttributes, SpanStatus, SpanTimeInput } from '../../../src/types-hoist';
+import type { SpanLink } from '../../../src/types-hoist/link';
 import type { OpenTelemetrySdkTraceBaseSpan } from '../../../src/utils/spanUtils';
+import { TRACE_FLAG_NONE, TRACE_FLAG_SAMPLED } from '../../../src/utils/spanUtils';
 import {
   getRootSpan,
   spanIsSampled,
@@ -156,6 +159,115 @@ describe('spanToTraceContext', () => {
   });
 });
 
+describe('convertSpanLinksForEnvelope', () => {
+  it('returns undefined for undefined input', () => {
+    expect(convertSpanLinksForEnvelope(undefined)).toBeUndefined();
+  });
+
+  it('returns undefined for empty array input', () => {
+    expect(convertSpanLinksForEnvelope([])).toBeUndefined();
+  });
+
+  it('converts a single span link to a flattened envelope item', () => {
+    const links: SpanLink[] = [
+      {
+        context: {
+          spanId: 'span1',
+          traceId: 'trace1',
+          traceFlags: TRACE_FLAG_SAMPLED,
+        },
+        attributes: {
+          'sentry.link.type': 'previous_trace',
+        },
+      },
+    ];
+
+    const result = convertSpanLinksForEnvelope(links);
+
+    result?.forEach(item => expect(item).not.toHaveProperty('context'));
+    expect(result).toEqual([
+      {
+        span_id: 'span1',
+        trace_id: 'trace1',
+        sampled: true,
+        attributes: {
+          'sentry.link.type': 'previous_trace',
+        },
+      },
+    ]);
+  });
+
+  it('converts multiple span links to a flattened envelope item', () => {
+    const links: SpanLink[] = [
+      {
+        context: {
+          spanId: 'span1',
+          traceId: 'trace1',
+          traceFlags: TRACE_FLAG_SAMPLED,
+        },
+        attributes: {
+          'sentry.link.type': 'previous_trace',
+        },
+      },
+      {
+        context: {
+          spanId: 'span2',
+          traceId: 'trace2',
+          traceFlags: TRACE_FLAG_NONE,
+        },
+        attributes: {
+          'sentry.link.type': 'another_trace',
+        },
+      },
+    ];
+
+    const result = convertSpanLinksForEnvelope(links);
+
+    result?.forEach(item => expect(item).not.toHaveProperty('context'));
+    expect(result).toEqual([
+      {
+        span_id: 'span1',
+        trace_id: 'trace1',
+        sampled: true,
+        attributes: {
+          'sentry.link.type': 'previous_trace',
+        },
+      },
+      {
+        span_id: 'span2',
+        trace_id: 'trace2',
+        sampled: false,
+        attributes: {
+          'sentry.link.type': 'another_trace',
+        },
+      },
+    ]);
+  });
+
+  it('handles span links without attributes', () => {
+    const links: SpanLink[] = [
+      {
+        context: {
+          spanId: 'span1',
+          traceId: 'trace1',
+          traceFlags: TRACE_FLAG_SAMPLED,
+        },
+      },
+    ];
+
+    const result = convertSpanLinksForEnvelope(links);
+
+    result?.forEach(item => expect(item).not.toHaveProperty('context'));
+    expect(result).toEqual([
+      {
+        span_id: 'span1',
+        trace_id: 'trace1',
+        sampled: true,
+      },
+    ]);
+  });
+});
+
 describe('spanTimeInputToSeconds', () => {
   it('works with undefined', () => {
     const now = timestampInSeconds();