feat: add outcome logging for tenant pools

src/config.test.ts

@@ -0,0 +1,95 @@
+import { vi } from 'vitest'
+
+const SAMPLE_RATE_ENV_KEYS = [
+  'MULTI_TENANT',
+  'IS_MULTITENANT',
+  'TENANT_POOL_CACHE_HIT_LOG_SAMPLE_RATE',
+  'TENANT_POOL_CACHE_MISS_LOG_SAMPLE_RATE',
+] as const
+
+type SampleRateEnvKey = (typeof SAMPLE_RATE_ENV_KEYS)[number]
+
+const originalEnv = new Map<SampleRateEnvKey, string | undefined>()
+
+function setSampleRateEnv(env: Partial<Record<SampleRateEnvKey, string>>) {
+  for (const key of SAMPLE_RATE_ENV_KEYS) {
+    delete process.env[key]
+  }
+
+  process.env.MULTI_TENANT = 'true'
+
+  for (const [key, value] of Object.entries(env)) {
+    process.env[key] = value
+  }
+}
+
+describe('config sample rate parsing', () => {
+  beforeAll(() => {
+    for (const key of SAMPLE_RATE_ENV_KEYS) {
+      originalEnv.set(key, process.env[key])
+    }
+  })
+
+  afterEach(() => {
+    for (const key of SAMPLE_RATE_ENV_KEYS) {
+      const value = originalEnv.get(key)
+
+      if (value === undefined) {
+        delete process.env[key]
+      } else {
+        process.env[key] = value
+      }
+    }
+
+    vi.resetModules()
+  })
+
+  test('defaults tenant pool cache log sample rates to zero', async () => {
+    setSampleRateEnv({})
+
+    const { getConfig } = await import('./config')
+    const config = getConfig({ reload: true })
+
+    expect(config.tenantPoolCacheHitLogSampleRate).toBe(0)
+    expect(config.tenantPoolCacheMissLogSampleRate).toBe(0)
+  })
+
+  test('parses fractional tenant pool cache log sample rates', async () => {
+    setSampleRateEnv({
+      TENANT_POOL_CACHE_HIT_LOG_SAMPLE_RATE: '0.25',
+      TENANT_POOL_CACHE_MISS_LOG_SAMPLE_RATE: '0.75',
+    })
+
+    const { getConfig } = await import('./config')
+    const config = getConfig({ reload: true })
+
+    expect(config.tenantPoolCacheHitLogSampleRate).toBe(0.25)
+    expect(config.tenantPoolCacheMissLogSampleRate).toBe(0.75)
+  })
+
+  test('clamps tenant pool cache log sample rates to zero and one', async () => {
+    setSampleRateEnv({
+      TENANT_POOL_CACHE_HIT_LOG_SAMPLE_RATE: '-0.5',
+      TENANT_POOL_CACHE_MISS_LOG_SAMPLE_RATE: '1.5',
+    })
+
+    const { getConfig } = await import('./config')
+    const config = getConfig({ reload: true })
+
+    expect(config.tenantPoolCacheHitLogSampleRate).toBe(0)
+    expect(config.tenantPoolCacheMissLogSampleRate).toBe(1)
+  })
+
+  test('falls back to default tenant pool cache log sample rates for invalid values', async () => {
+    setSampleRateEnv({
+      TENANT_POOL_CACHE_HIT_LOG_SAMPLE_RATE: 'nope',
+      TENANT_POOL_CACHE_MISS_LOG_SAMPLE_RATE: 'Infinity',
+    })
+
+    const { getConfig } = await import('./config')
+    const config = getConfig({ reload: true })
+
+    expect(config.tenantPoolCacheHitLogSampleRate).toBe(0)
+    expect(config.tenantPoolCacheMissLogSampleRate).toBe(0)
+  })
+})

src/config.ts

@@ -186,6 +186,8 @@ type StorageConfigType = {
   }
   prometheusMetricsEnabled: boolean
   prometheusMetricsIncludeTenantId: boolean
+  tenantPoolCacheHitLogSampleRate: number
+  tenantPoolCacheMissLogSampleRate: number
   otelMetricsEnabled: boolean
   otelMetricsTemporality: 'DELTA' | 'CUMULATIVE'
   otelMetricsExportIntervalMs: number
@@ -456,6 +458,14 @@ export function getConfig(options?: { reload?: boolean }): StorageConfigType {
     logflareApiKey: getOptionalConfigFromEnv('LOGFLARE_API_KEY'),
     logflareSourceToken: getOptionalConfigFromEnv('LOGFLARE_SOURCE_TOKEN'),
     logflareBatchSize: parseInt(getOptionalConfigFromEnv('LOGFLARE_BATCH_SIZE') || '200', 10),
+    tenantPoolCacheHitLogSampleRate: envSampleRate(
+      getOptionalConfigFromEnv('TENANT_POOL_CACHE_HIT_LOG_SAMPLE_RATE'),
+      0
+    ),
+    tenantPoolCacheMissLogSampleRate: envSampleRate(
+      getOptionalConfigFromEnv('TENANT_POOL_CACHE_MISS_LOG_SAMPLE_RATE'),
+      0
+    ),
     tracingEnabled: getOptionalConfigFromEnv('TRACING_ENABLED') === 'true',
     tracingMode: getOptionalConfigFromEnv('TRACING_MODE') ?? 'basic',
     tracingTimeMinDuration: parseFloat(
@@ -646,3 +656,16 @@ function envNumber(value: string | undefined, defaultValue?: number): number | u
   }
   return parsed
 }
+
+function envSampleRate(value: string | undefined, defaultValue: number): number {
+  if (!value) {
+    return defaultValue
+  }
+
+  const parsed = Number(value)
+  if (!Number.isFinite(parsed)) {
+    return defaultValue
+  }
+
+  return Math.min(Math.max(parsed, 0), 1)
+}