Support for custom log level mapping

examples/basic.ts

@@ -1,6 +1,6 @@
 import 'dotenv/config'
 import { pino } from 'pino'
-import { LokiOptions } from '../src/types/index'
+import { LokiOptions, LokiLogLevel } from '../src/types/index'
 
 const transport = pino.transport<LokiOptions>({
   // 👇 Replace this with "pino-loki"
@@ -9,7 +9,11 @@ const transport = pino.transport<LokiOptions>({
   options: {
     // These labels will be added to every log
     labels: { application: 'MY-APP' },
-
+    // custom log levels
+    levelMap: {
+      '5': LokiLogLevel.Debug, // Add a custom log level
+      '10': LokiLogLevel.Info, // Override a default mapping
+    },
     // Credentials for our Loki instance
     host: process.env.LOKI_HOST!,
     basicAuth: {

src/index.ts

@@ -1,5 +1,5 @@
 import abstractTransportBuild from 'pino-abstract-transport'
-import { PinoLog, LokiOptions } from './types/index'
+import { PinoLog, LokiOptions, LokiLogLevel } from './types/index'
 import { LogPusher } from './log_pusher/index'
 import debug from './debug'
 
@@ -68,3 +68,4 @@ function pinoLoki(userOptions: LokiOptions) {
 
 export default pinoLoki
 export type { LokiOptions }
+export { LokiLogLevel }

src/log_builder/index.ts

@@ -1,33 +1,37 @@
-import { LokiLog, LokiLogLevel, PinoLog } from '../types/index'
+import { LokiLog, LokiLogLevel, PinoLog, LokiOptions } from '../types/index'
 
 const NANOSECONDS_LENGTH = 19
 
+type BuilderOptions = Pick<LokiOptions, 'propsToLabels' | 'levelMap'>
+
 /**
  * Converts a Pino log to a Loki log
  */
 export class LogBuilder {
-  #propsToLabel: string[]
-
-  constructor(propsToLabel: string[] = []) {
-    this.#propsToLabel = propsToLabel
-  }
+  #propsToLabels: string[]
+  #levelMap: { [key: number]: LokiLogLevel }
 
-  /**
-   * Convert a level to a human readable status
-   */
-  public statusFromLevel(level: number) {
-    return (
+  constructor(options?: BuilderOptions) {
+    this.#propsToLabels = options?.propsToLabels || []
+    this.#levelMap = Object.assign(
       {
         10: LokiLogLevel.Debug,
         20: LokiLogLevel.Debug,
         30: LokiLogLevel.Info,
         40: LokiLogLevel.Warning,
         50: LokiLogLevel.Error,
         60: LokiLogLevel.Critical,
-      }[level] || LokiLogLevel.Info
+      },
+      options?.levelMap,
     )
   }
 
+  /**
+   * Convert a level to a human readable status
+   */
+  public statusFromLevel(level: number) {
+    return this.#levelMap[level] || LokiLogLevel.Info
+  }
   /**
    * Builds a timestamp string from a Pino log object.
    * @returns A string representing the timestamp in nanoseconds.
@@ -53,7 +57,7 @@ export class LogBuilder {
   #buildLabelsFromProps(log: PinoLog) {
     const labels: Record<string, string> = {}
 
-    for (const prop of this.#propsToLabel) {
+    for (const prop of this.#propsToLabels) {
       if (log[prop]) {
         labels[prop] = log[prop]
       }

src/log_pusher/index.ts

@@ -24,8 +24,10 @@ export class LogPusher {
       }),
     })
 
-    const propsToLabels = options.propsToLabels || []
-    this.#logBuilder = new LogBuilder(propsToLabels)
+    this.#logBuilder = new LogBuilder({
+      levelMap: options.levelMap,
+      propsToLabels: options.propsToLabels,
+    })
   }
 
   /**

src/types/index.ts

@@ -72,6 +72,21 @@ export interface LokiOptions {
     [key: string]: string
   }
 
+  /**
+   * Custom pino to loki log level mapping, merged with the default one.
+   * @default
+   *    10: LokiLogLevel.Debug,
+        20: LokiLogLevel.Debug,
+        30: LokiLogLevel.Info,
+        40: LokiLogLevel.Warning,
+        50: LokiLogLevel.Error,
+        60: LokiLogLevel.Critical
+   */
+
+  levelMap?: {
+    [key: number]: LokiLogLevel
+  }
+
   /**
    * Basic auth credentials to be used when sending logs to Loki
    */

tests/unit/log_builder.spec.ts

@@ -1,5 +1,5 @@
 import { test } from '@japa/runner'
-import { PinoLog } from '../../src/types/index'
+import { LokiLogLevel, PinoLog } from '../../src/types/index'
 import { LogBuilder } from '../../src/log_builder/index'
 import { sleep } from '../../src/utils/index'
 
@@ -23,6 +23,19 @@ test.group('Log Builder', () => {
     assert.deepEqual(logBuilder.statusFromLevel(60), 'critical')
   })
 
+  test('Custom levels', ({ assert }) => {
+    const logBuilder = new LogBuilder({
+      levelMap: { '5': LokiLogLevel.Debug, '20': LokiLogLevel.Info },
+    })
+    assert.deepEqual(logBuilder.statusFromLevel(5), 'debug') // custom
+    assert.deepEqual(logBuilder.statusFromLevel(10), 'debug')
+    assert.deepEqual(logBuilder.statusFromLevel(20), 'info') // override
+    assert.deepEqual(logBuilder.statusFromLevel(30), 'info')
+    assert.deepEqual(logBuilder.statusFromLevel(40), 'warning')
+    assert.deepEqual(logBuilder.statusFromLevel(50), 'error')
+    assert.deepEqual(logBuilder.statusFromLevel(60), 'critical')
+  })
+
   test('Build a loki log entry from a pino log', ({ assert }) => {
     const logBuilder = new LogBuilder()
 
@@ -66,7 +79,7 @@ test.group('Log Builder', () => {
   })
 
   test('Props to label', ({ assert }) => {
-    const logBuilder = new LogBuilder(['appId', 'buildId'])
+    const logBuilder = new LogBuilder({ propsToLabels: ['appId', 'buildId'] })
 
     const log: PinoLog = {
       hostname: 'localhost',