[ObsPresentation][APM] Handle malformed span.links data in trace samples

x-pack/solutions/observability/plugins/apm/server/routes/span_links/get_linked_children.test.ts

@@ -0,0 +1,140 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import type { APMEventClient } from '../../lib/helpers/create_es_client/create_apm_event_client';
+import { getSpanLinksCountById, getLinkedChildrenOfSpan } from './get_linked_children';
+
+describe('get_linked_children', () => {
+  const mockApmEventClient = {
+    search: jest.fn(),
+  } as unknown as APMEventClient;
+
+  const defaultParams = {
+    traceId: 'test-trace-id',
+    apmEventClient: mockApmEventClient,
+    start: 0,
+    end: 1000,
+  };
+
+  const createHit = (
+    spanLinks: any,
+    fields: Record<string, string[]> = { 'trace.id': ['test-trace-id'], 'span.id': ['span-1'] }
+  ) => ({
+    _source: { span: { links: spanLinks } },
+    fields,
+  });
+
+  const mockSearchWith = (hits: any[]) => {
+    (mockApmEventClient.search as jest.Mock).mockResolvedValue({ hits: { hits } });
+  };
+
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  describe('getSpanLinksCountById', () => {
+    it('should return counts for span links grouped by span id', async () => {
+      mockSearchWith([
+        createHit([
+          { trace: { id: 'test-trace-id' }, span: { id: 'span-1' } },
+          { trace: { id: 'test-trace-id' }, span: { id: 'span-2' } },
+        ]),
+        createHit([{ trace: { id: 'test-trace-id' }, span: { id: 'span-1' } }]),
+      ]);
+
+      const result = await getSpanLinksCountById(defaultParams);
+
+      expect(result).toEqual({ 'span-1': 2, 'span-2': 1 });
+    });
+
+    it('should wrap single span link object in array', async () => {
+      mockSearchWith([createHit({ trace: { id: 'test-trace-id' }, span: { id: 'span-1' } })]);
+
+      const result = await getSpanLinksCountById(defaultParams);
+
+      expect(result).toEqual({ 'span-1': 1 });
+    });
+
+    it('should filter out span links from different traces', async () => {
+      mockSearchWith([
+        createHit([
+          { trace: { id: 'test-trace-id' }, span: { id: 'span-1' } },
+          { trace: { id: 'different-trace-id' }, span: { id: 'span-2' } },
+        ]),
+      ]);
+
+      const result = await getSpanLinksCountById(defaultParams);
+
+      expect(result).toEqual({ 'span-1': 1 });
+    });
+
+    it('should return empty object when no span links found', async () => {
+      mockSearchWith([]);
+
+      const result = await getSpanLinksCountById(defaultParams);
+
+      expect(result).toEqual({});
+    });
+  });
+
+  describe('getLinkedChildrenOfSpan', () => {
+    it('should return linked children for a specific span', async () => {
+      mockSearchWith([
+        createHit([{ trace: { id: 'test-trace-id' }, span: { id: 'target-span-id' } }], {
+          'trace.id': ['test-trace-id'],
+          'span.id': ['child-span-1'],
+        }),
+      ]);
+
+      const result = await getLinkedChildrenOfSpan({ ...defaultParams, spanId: 'target-span-id' });
+
+      expect(result).toEqual([{ trace: { id: 'test-trace-id' }, span: { id: 'child-span-1' } }]);
+    });
+
+    it('should wrap single span link object in array', async () => {
+      mockSearchWith([
+        createHit(
+          { trace: { id: 'test-trace-id' }, span: { id: 'target-span-id' } },
+          { 'trace.id': ['test-trace-id'], 'span.id': ['child-span-1'] }
+        ),
+      ]);
+
+      const result = await getLinkedChildrenOfSpan({ ...defaultParams, spanId: 'target-span-id' });
+
+      expect(result).toEqual([{ trace: { id: 'test-trace-id' }, span: { id: 'child-span-1' } }]);
+    });
+
+    it('should use transaction.id when span.id is not available', async () => {
+      mockSearchWith([
+        createHit([{ trace: { id: 'test-trace-id' }, span: { id: 'target-span-id' } }], {
+          'trace.id': ['test-trace-id'],
+          'transaction.id': ['transaction-1'],
+        }),
+      ]);
+
+      const result = await getLinkedChildrenOfSpan({ ...defaultParams, spanId: 'target-span-id' });
+
+      expect(result).toEqual([{ trace: { id: 'test-trace-id' }, span: { id: 'transaction-1' } }]);
+    });
+
+    it('should filter out links that do not match the target spanId', async () => {
+      mockSearchWith([
+        createHit(
+          [
+            { trace: { id: 'test-trace-id' }, span: { id: 'target-span-id' } },
+            { trace: { id: 'test-trace-id' }, span: { id: 'different-span-id' } },
+          ],
+          { 'trace.id': ['test-trace-id'], 'span.id': ['child-span-1'] }
+        ),
+      ]);
+
+      const result = await getLinkedChildrenOfSpan({ ...defaultParams, spanId: 'target-span-id' });
+
+      expect(result).toEqual([{ trace: { id: 'test-trace-id' }, span: { id: 'child-span-1' } }]);
+    });
+  });
+});

x-pack/solutions/observability/plugins/apm/server/routes/span_links/get_linked_children.ts

@@ -94,10 +94,15 @@ async function fetchLinkedChildrenOfSpan({
     const source = 'span' in hit._source ? hit._source : undefined;
     const event = accessKnownApmEventFields(hit.fields).requireFields(requiredFields).build();
 
+    const spanLinksArray = source?.span?.links
+      ? Array.isArray(source?.span?.links)
+        ? source.span.links
+        : [source.span.links]
+      : undefined;
     return {
       ...event,
       [SPAN_LINKS]:
-        source?.span?.links ??
+        spanLinksArray ??
         mapOtelToSpanLink({
           trace_id: event[OTEL_SPAN_LINKS_TRACE_ID],
           span_id: event[OTEL_SPAN_LINKS_SPAN_ID],