feat(Throttling): Allow for throttling of events in handler

index.test.ts

@@ -5,7 +5,8 @@ import {
   LogLevel,
   removeHandler,
   removeHandlers,
-  replaceHandlers
+  replaceHandlers,
+  defaultHandler
 } from './index'
 
 test('logging', () => {
@@ -40,7 +41,6 @@ test('logging', () => {
   expect(events[3].stack).toMatch(/^Error:/)
   // Second line (first call stack) in stack trace should be this file
   expect(events[3].stack.split('\n')[1]).toMatch(/logga\/index\.test\.ts/)
-
 })
 
 test('TTY', () => {
@@ -108,3 +108,50 @@ test('adding and removing handlers', () => {
   // no more logging to console
   expect(consoleError.mock.calls.length).toBe(consoleErrorCalls)
 })
+
+test('defaultHandler:level', () => {
+  const log = getLogger('logger')
+
+  const consoleError = jest.spyOn(console, 'error')
+  const callsStart = consoleError.mock.calls.length
+
+  log.debug('a debug message')
+  expect(consoleError.mock.calls.length).toBe(callsStart + 0)
+
+  replaceHandlers(data => defaultHandler(data, { level: LogLevel.debug }))
+  log.debug('a debug message')
+  expect(consoleError.mock.calls.length).toBe(callsStart + 1)
+
+  replaceHandlers(data => defaultHandler(data, { level: LogLevel.warn }))
+  log.debug('a debug message')
+  log.warn('a warn message')
+  expect(consoleError.mock.calls.length).toBe(callsStart + 2)
+
+  removeHandlers()
+})
+
+test('defaultHandler:throttle', async () => {
+  const log = getLogger('logger')
+
+  const consoleError = jest.spyOn(console, 'error')
+  const callsStart = consoleError.mock.calls.length
+
+  replaceHandlers(data => defaultHandler(data, { throttle: { signature: '${message}', duration: 200 } }))
+
+  log.error('a message')
+  expect(consoleError.mock.calls.length).toBe(callsStart + 1)
+
+  log.error('a message')
+  expect(consoleError.mock.calls.length).toBe(callsStart + 1)
+
+  await (new Promise(resolve => setTimeout(resolve, 300)))
+
+  log.error('a message')
+  expect(consoleError.mock.calls.length).toBe(callsStart + 2)
+
+  log.error('a different message')
+  expect(consoleError.mock.calls.length).toBe(callsStart + 3)
+
+  removeHandlers()
+})
+

index.ts

@@ -102,6 +102,8 @@ export function replaceHandlers(handler: LogHandler) {
   addHandler(handler)
 }
 
+const defaultHandlerHistory = new Map<string, number>()
+
 /**
  * Default log data handler.
  *
@@ -111,8 +113,47 @@ export function replaceHandlers(handler: LogHandler) {
  * - as JSON if stderr is not TTY (for machine consumption e.g. log files)
  *
  * @param data The log data to handle
+ * @param level The maximum log level to print. Defaults to `info`
+ * @param throttle.signature The log event signature to use for throttling. Defaults to '' (i.e. all events)
+ * @param throttle.duration The duration for throttling (milliseconds). Defaults to 1000ms
  */
-export function defaultHandler(data: LogData) {
+export function defaultHandler(
+  data: LogData,
+  options?: {
+    level?: LogLevel
+    throttle?: {
+      signature?: string
+      duration?: number
+    }
+  }
+) {
+  // Skip if greater than desired reporting level
+  const level =
+    options !== undefined && options.level !== undefined
+      ? options.level
+      : LogLevel.info
+  if (data.level > level) return
+
+  // Skip if within throttling duration for the event signature
+  const throttle = options !== undefined ? options.throttle : undefined
+  if (throttle !== undefined) {
+    const signature = throttle.signature !== undefined
+        ? throttle.signature
+        : ''
+    const eventSignature = signature
+      .replace(/\${tag}/, data.tag)
+      .replace(/\${level}/, data.level.toString())
+      .replace(/\${message}/, data.message)
+    const lastTime = defaultHandlerHistory.get(eventSignature)
+    if (lastTime !== undefined) {
+      const duration = throttle.duration !== undefined
+          ? throttle.duration
+          : 1000
+      if ((Date.now() - lastTime) < duration) return
+    }
+    defaultHandlerHistory.set(eventSignature, Date.now())
+  }
+
   let entry
   if (process.stderr.isTTY) {
     const { tag, level, message, stack } = data
@@ -133,7 +174,7 @@ export function defaultHandler(data: LogData) {
     const cyan = '\u001b[36m'
     const reset = '\u001b[0m'
     entry = `${emoji} ${colour}${label}${reset} ${cyan}${tag}${reset} ${message}`
-    if (level === LogLevel.error) entry += '\n  ' + stack
+    if (entry.stack) entry += '\n  ' + stack
   } else {
     entry = JSON.stringify({ time: new Date().toISOString(), ...data })
   }

package.json

@@ -10,8 +10,8 @@
   "scripts": {
     "format": "npx prettier --write './**/*.{md,ts}'",
     "lint": "eslint 'src/**/*.{ts,js}' --fix",
-    "test": "jest",
-    "test:cover": "jest --collectCoverage",
+    "test": "jest --runInBand",
+    "test:cover": "jest  --runInBand --collectCoverage",
     "build": "tsc index.ts --outDir dist --declaration"
   },
   "repository": {