FFM-11788 Add maxStreamRetries config option (#126)

Author: erdirowlands

README.md

@@ -119,6 +119,32 @@ const client = initialize(
 )
 ```
 
+Max Stream Retries
+You can configure the maximum number of streaming retries before the SDK stops attempting to reconnect or falls back to polling (if enabled). The maxRetries option can be set to any positive number or Infinity for unlimited retries (which is the default).
+
+```typescript
+const options = {
+  maxRetries: 5, // Set the maximum number of retries for streaming. Default is Infinity.
+  streamEnabled: true, 
+  pollingEnabled: true, 
+  pollingInterval: 60000, 
+}
+
+const client = initialize(
+    'YOUR_SDK_KEY',
+    {
+      identifier: 'Harness1',
+      attributes: {
+        lastUpdated: Date(),
+        host: location.href
+      }
+    },
+    options
+)
+
+```
+If maxRetries is reached and pollingEnabled is true, the SDK will stay in polling mode. If pollingEnabled is false, the SDK will not poll, and evaluations will not be updated until the SDK Client is initialized again, for example if the app or page is restarted.
+
 ## Listening to events from the `client` instance.
 
 ```typescript

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "@harnessio/ff-javascript-client-sdk",
-  "version": "1.26.3",
+  "version": "1.27.0-rc.0",
   "author": "Harness",
   "license": "Apache-2.0",
   "main": "dist/sdk.cjs.js",

package.json

@@ -0,0 +1,247 @@
+import { Streamer } from '../stream'
+import type { Options } from '../types'
+import { Event } from '../types'
+import { getRandom } from '../utils'
+import type { Emitter } from 'mitt'
+import type Poller from "../poller";
+
+jest.useFakeTimers()
+
+jest.mock('../utils.ts', () => ({
+  getRandom: jest.fn()
+}))
+
+const mockEventBus: Emitter = {
+  emit: jest.fn(),
+  on: jest.fn(),
+  off: jest.fn(),
+  all: new Map()
+}
+
+const mockXHR = {
+  open: jest.fn(),
+  setRequestHeader: jest.fn(),
+  send: jest.fn(),
+  abort: jest.fn(),
+  status: 0,
+  responseText: '',
+  onload: null,
+  onerror: null,
+  onprogress: null,
+  onabort: null,
+  ontimeout: null
+}
+
+global.XMLHttpRequest = jest.fn(() => mockXHR) as unknown as jest.MockedClass<typeof XMLHttpRequest>
+
+const logError = jest.fn()
+const logDebug = jest.fn()
+
+const getStreamer = (overrides: Partial<Options> = {}, maxRetries: number = Infinity): Streamer => {
+  const options: Options = {
+    baseUrl: 'http://test',
+    eventUrl: 'http://event',
+    pollingInterval: 60000,
+    debug: true,
+    pollingEnabled: true,
+    streamEnabled: true,
+    ...overrides
+  }
+
+  return new Streamer(
+      mockEventBus,
+      options,
+      `${options.baseUrl}/stream`,
+      'test-api-key',
+      { 'Test-Header': 'value' },
+      { start: jest.fn(), stop: jest.fn(), isPolling: jest.fn() } as unknown as Poller,
+      logDebug,
+      logError,
+      jest.fn(),
+      maxRetries
+  )
+}
+
+describe('Streamer', () => {
+  beforeEach(() => {
+    jest.clearAllMocks()
+  })
+
+  it('should connect and emit CONNECTED event', () => {
+    const streamer = getStreamer({}, 3)
+
+    streamer.start()
+    expect(mockXHR.open).toHaveBeenCalledWith('GET', 'http://test/stream')
+    expect(mockXHR.send).toHaveBeenCalled()
+
+    mockXHR.onprogress({} as ProgressEvent)
+    expect(mockEventBus.emit).toHaveBeenCalledWith(Event.CONNECTED)
+  })
+
+  it('should reconnect successfully after multiple failures', () => {
+    const streamer = getStreamer({}, 5)
+
+    streamer.start()
+    expect(mockXHR.send).toHaveBeenCalled()
+
+    for (let i = 0; i < 3; i++) {
+      mockXHR.onerror({} as ProgressEvent)
+      jest.advanceTimersByTime(getRandom(1000, 10000))
+    }
+
+    // Simulate a successful connection on the next attempt
+    mockXHR.onprogress({} as ProgressEvent)
+
+    expect(mockEventBus.emit).toHaveBeenCalledWith(Event.CONNECTED)
+    expect(mockXHR.send).toHaveBeenCalledTimes(4) // Should attempt to reconnect 3 times before succeeding
+  })
+
+  it('should retry connecting on error and eventually fallback to polling', () => {
+    const streamer = getStreamer()
+
+    streamer.start()
+    expect(mockXHR.send).toHaveBeenCalled()
+
+    for (let i = 0; i < 3; i++) {
+      mockXHR.onerror({} as ProgressEvent)
+      jest.advanceTimersByTime(getRandom(1000, 10000))
+    }
+
+    expect(mockEventBus.emit).toHaveBeenCalledWith(Event.DISCONNECTED)
+  })
+
+  it('should not retry after max retries are exhausted', () => {
+    const streamer = getStreamer({}, 3)
+
+    streamer.start()
+    expect(mockXHR.send).toHaveBeenCalled()
+
+    for (let i = 0; i < 3; i++) {
+      mockXHR.onerror({} as ProgressEvent)
+      jest.advanceTimersByTime(getRandom(1000, 10000))
+    }
+
+    mockXHR.onerror({} as ProgressEvent)
+    expect(logError).toHaveBeenCalledWith('Streaming:  Max streaming retries reached. Staying in polling mode.')
+    expect(mockEventBus.emit).toHaveBeenCalledWith(Event.DISCONNECTED)
+    expect(mockXHR.send).toHaveBeenCalledTimes(3) // Should not send after max retries
+  })
+
+  it('should fallback to polling on stream failure', () => {
+    const poller = { start: jest.fn(), stop: jest.fn(), isPolling: jest.fn() } as unknown as Poller
+    const streamer = new Streamer(
+        mockEventBus,
+        { baseUrl: 'http://test', eventUrl: 'http://event', pollingEnabled: true, streamEnabled: true, debug: true },
+        'http://test/stream',
+        'test-api-key',
+        { 'Test-Header': 'value' },
+        poller,
+        logDebug,
+        logError,
+        jest.fn(),
+        Infinity
+    )
+
+    streamer.start()
+    expect(mockXHR.send).toHaveBeenCalled()
+
+    mockXHR.onerror({} as ProgressEvent)
+    jest.advanceTimersByTime(getRandom(1000, 10000))
+
+    expect(poller.start).toHaveBeenCalled()
+    expect(logDebug).toHaveBeenCalledWith('Streaming:  Falling back to polling mode while stream recovers')
+  })
+
+  it('should stop polling when close is called if in fallback polling mode', () => {
+    const poller = { start: jest.fn(), stop: jest.fn(), isPolling: jest.fn() } as unknown as Poller
+    ;(poller.isPolling as jest.Mock)
+        .mockImplementationOnce(() => false)
+        .mockImplementationOnce(() => true)
+
+    const streamer = new Streamer(
+        mockEventBus,
+        { baseUrl: 'http://test', eventUrl: 'http://event', pollingEnabled: true, streamEnabled: true, debug: true },
+        'http://test/stream',
+        'test-api-key',
+        { 'Test-Header': 'value' },
+        poller,
+        logDebug,
+        logError,
+        jest.fn(),
+        3
+    )
+
+    streamer.start()
+    expect(mockXHR.send).toHaveBeenCalled()
+
+    // Simulate stream failure and fallback to polling
+    mockXHR.onerror({} as ProgressEvent)
+    jest.advanceTimersByTime(getRandom(1000, 10000))
+
+    // Ensure polling has started
+    expect(poller.start).toHaveBeenCalled()
+
+    // Now close the streamer
+    streamer.close()
+
+    expect(mockXHR.abort).toHaveBeenCalled()
+    expect(poller.stop).toHaveBeenCalled()
+    expect(mockEventBus.emit).toHaveBeenCalledWith(Event.STOPPED)
+  })
+
+  it('should stop streaming but not call poller.stop if not in fallback polling mode when close is called', () => {
+    const poller = { start: jest.fn(), stop: jest.fn(), isPolling: jest.fn().mockReturnValue(false) } as unknown as Poller
+    const streamer = new Streamer(
+        mockEventBus,
+        { baseUrl: 'http://test', eventUrl: 'http://event', pollingEnabled: true, streamEnabled: true, debug: true },
+        'http://test/stream',
+        'test-api-key',
+        { 'Test-Header': 'value' },
+        poller,
+        logDebug,
+        logError,
+        jest.fn(),
+        3
+    )
+
+    streamer.start()
+    streamer.close()
+
+    expect(mockXHR.abort).toHaveBeenCalled()
+    expect(poller.stop).not.toHaveBeenCalled()
+    expect(mockEventBus.emit).toHaveBeenCalledWith(Event.STOPPED)
+  })
+
+  it('should retry indefinitely if maxRetries is set to Infinity', () => {
+    const streamer = getStreamer()
+
+    streamer.start()
+    expect(mockXHR.send).toHaveBeenCalled()
+
+    for (let i = 0; i < 100; i++) {
+      mockXHR.onerror({} as ProgressEvent)
+      jest.advanceTimersByTime(getRandom(1000, 10000))
+    }
+
+    expect(logError).not.toHaveBeenCalledWith('Streaming:  Max streaming retries reached. Staying in polling mode.')
+    expect(mockXHR.send).toHaveBeenCalledTimes(101)
+  })
+
+  it('should reconnect successfully after multiple failures', () => {
+    const streamer = getStreamer({}, 5)
+
+    streamer.start()
+    expect(mockXHR.send).toHaveBeenCalled()
+
+    for (let i = 0; i < 3; i++) {
+      mockXHR.onerror({} as ProgressEvent)
+      jest.advanceTimersByTime(getRandom(1000, 10000))
+    }
+
+    // Simulate a successful connection on the next attempt
+    mockXHR.onprogress({} as ProgressEvent)
+
+    expect(mockEventBus.emit).toHaveBeenCalledWith(Event.CONNECTED)
+    expect(mockXHR.send).toHaveBeenCalledTimes(4) // Should attempt to reconnect 3 times before succeeding
+  })
+})

src/__tests__/stream.test.ts

@@ -543,7 +543,8 @@ const initialize = (apiKey: string, target: Target, options?: Options): Result =
         } else if (event.domain === 'target-segment') {
           handleSegmentEvent(event)
         }
-      }
+      },
+      configurations.maxStreamRetries
     )
     eventSource.start()
   }

src/index.ts

@@ -11,7 +11,8 @@ export class Streamer {
   private readTimeoutCheckerId: any
   private connectionOpened = false
   private disconnectEventEmitted = false
-  private reconnectAttempts = 0 
+  private reconnectAttempts = 0
+  private retriesExhausted: boolean = false
 
   constructor(
     private eventBus: Emitter,
@@ -22,7 +23,8 @@ export class Streamer {
     private fallbackPoller: Poller,
     private logDebug: (...data: any[]) => void,
     private logError: (...data: any[]) => void,
-    private eventCallback: (e: StreamEvent) => void
+    private eventCallback: (e: StreamEvent) => void,
+    private maxRetries: number
   ) {}
 
   start() {
@@ -60,10 +62,26 @@ export class Streamer {
         )
       }
 
+      if (this.reconnectAttempts >= this.maxRetries) {
+        this.retriesExhausted = true
+        if (this.configurations.pollingEnabled) {
+          this.logErrorMessage('Max streaming retries reached. Staying in polling mode.')
+        } else {
+          this.logErrorMessage(
+            'Max streaming retries reached. Polling mode is disabled and will receive no further flag updates until SDK client is restarted.'
+          )
+        }
+        return
+      }
+
       setTimeout(() => this.start(), reconnectDelayMs)
     }
 
     const onFailed = (msg: string) => {
+      if (this.retriesExhausted) {
+        return
+      }
+
       if (!!msg) {
         this.logDebugMessage('Stream has issue', msg)
       }

src/stream.ts

@@ -144,6 +144,12 @@ export interface Options {
    * @default console
    */
   logger?: Logger
+
+  /**
+   * By default, the stream will attempt to reconnect indefinitely if it disconnects. Use this option to limit
+   * the number of attempts it will make.
+   */
+  maxStreamRetries?: number
 }
 
 export interface MetricsInfo {

src/types.ts

@@ -10,7 +10,8 @@ export const defaultOptions: Options = {
   eventsSyncInterval: MIN_EVENTS_SYNC_INTERVAL,
   pollingInterval: MIN_POLLING_INTERVAL,
   streamEnabled: true,
-  cache: false
+  cache: false,
+  maxStreamRetries: Infinity
 }
 
 export const getConfiguration = (options: Options): Options => {