Plugins

Plugins extend logger functionality by transforming or filtering logs before they reach transports.

Overview

Plugins hook into the logging pipeline to:

• Filter logs based on level, namespace, or custom criteria
• Transform log data by adding, removing, or modifying fields
• Redact sensitive information like passwords or API keys
• Add context from global state or async local storage

const logger = createLogger({
  namespace: 'my-app',
  plugins: [
    createFilterPlugin({ minLevel: 'info' }),
    createRedactPlugin({ paths: ['password'] }),
    createGlobalLogContextPlugin()
  ]
});

Plugin Pipeline

Plugins execute in two phases:

Log Call
   ↓
plugins shouldLog (filtering)
   ↓
plugins transformLogContext (transformation)
   ↓
Transports

If any shouldLog plugin returns false, the log is dropped and never reaches transports.

Built-in Plugins

Crowlog provides four built-in plugins:

• Filter Plugin - Filter logs by level, namespace, or custom logic
• Redact Plugin - Automatically redact sensitive fields
• Global Log Context Plugin - Add application-wide context
• Async Context Plugin - Add async request-scoped context

Order Matters

Plugins execute in the order they're defined:

createLogger({
  namespace: 'my-app',
  plugins: [
    createFilterPlugin({ minLevel: 'info' }), // Runs first
    createRedactPlugin({ paths: ['password'] }) // Runs second
  ]
});

Next Steps

• Child Loggers - Create child loggers with inherited configuration
• Testing - Test your logging with in-memory transport
• Custom Plugins - Create your own plugins