feat: observe BI data source health

src/server/source-telemetry.test.ts

@@ -0,0 +1,58 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import {
+  clearDataSourceTelemetry,
+  getDataSourceTelemetry,
+  observeDataSource,
+  recordDataSourceOutcome,
+} from './source-telemetry.js';
+
+test('reports unobserved sources without treating them as failures', () => {
+  clearDataSourceTelemetry();
+  const report = getDataSourceTelemetry(new Date('2026-08-07T08:00:00Z'));
+  assert.ok(report.sources.every(source => source.state === 'unobserved'));
+  assert.ok(report.sources.every(source => source.failureRate === null));
+});
+
+test('publishes rolling outcomes and last success/failure timestamps', () => {
+  clearDataSourceTelemetry();
+  recordDataSourceOutcome('oneOsMileage', true, 1_000);
+  recordDataSourceOutcome('oneOsMileage', false, 2_000);
+  const source = getDataSourceTelemetry().sources.find(item => item.source === 'oneOsMileage');
+  assert.deepEqual(source && {
+    state: source.state,
+    attempts: source.attempts,
+    failures: source.failures,
+    failureRate: source.failureRate,
+    lastSuccessAt: source.lastSuccessAt,
+    lastFailureAt: source.lastFailureAt,
+  }, {
+    state: 'failing',
+    attempts: 2,
+    failures: 1,
+    failureRate: 0.5,
+    lastSuccessAt: '1970-01-01T00:00:01.000Z',
+    lastFailureAt: '1970-01-01T00:00:02.000Z',
+  });
+});
+
+test('observes final operation outcomes without retaining error details', async () => {
+  clearDataSourceTelemetry();
+  await assert.rejects(observeDataSource('hydrogenDatabase', async () => {
+    throw new Error('sensitive connection detail');
+  }));
+  const serialized = JSON.stringify(getDataSourceTelemetry());
+  assert.equal(serialized.includes('sensitive connection detail'), false);
+});
+
+test('keeps only the latest 100 outcomes', () => {
+  clearDataSourceTelemetry();
+  recordDataSourceOutcome('etcDatabase', false, 1);
+  for (let index = 0; index < 100; index += 1) {
+    recordDataSourceOutcome('etcDatabase', true, index + 2);
+  }
+  const source = getDataSourceTelemetry().sources.find(item => item.source === 'etcDatabase');
+  assert.equal(source?.attempts, 100);
+  assert.equal(source?.failures, 0);
+  assert.equal(source?.failureRate, 0);
+});