Observers

Observers

Observers are powerful components in Raindrop that let you execute code in response to changes in your resources. Think of them as event listeners that automatically trigger when specific conditions are met in your application.

Types of Observers

Raindrop provides two types of observers to help you build reactive applications:

• Object Observers: Monitor changes to objects in buckets
• Queue Observers: Process messages as they arrive in queues

Object Observers

Object observers watch for changes to objects in your buckets and execute code in response. They’re particularly useful when you need to process files after upload.

To create an object observer, add it to your raindrop.manifest.

Note

When you run raindrop build generate, Raindrop automatically sets up the function code, bucket configuration, and all required service bindings for your observer.

raindrop.manifest

application "demo" {
  // First define your bucket
  bucket "observed-bucket" {}

  // Then create an observer
  observer "my-observer" {
    source {
      bucket = "observed-bucket"
      rule {
        // Specify which actions should trigger the observer
        actions = ["PutObject", "CompleteMultipartUpload", "CopyObject"]
      }
    }
  }
}

index.ts

import { Each } from '@liquidmetal-ai/raindrop-framework';
import { Env } from './raindrop.gen';

export default class extends Each<Body, Env> {
  async process(message: observers.BucketEventNotification): Promise<void> {
    console.log(`received message: ${JSON.stringify(message)}`);
  }
}

Supported Trigger Actions

Your observer can respond to the following bucket events:

Object Creation Events

• PutObject - Triggers when objects are uploaded directly
• CopyObject - Triggers when objects are copied
• CompleteMultipartUpload - Triggers when multipart uploads finish

Object Deletion Events

• DeleteObject - Triggers on manual object deletion
• LifecycleDeletion - Triggers when objects are deleted by lifecycle rules

Queue Observers

Queue observers process messages as they arrive in a queue. They’re the perfect solution for handling asynchronous tasks and managing background jobs that shouldn’t block your main application flow.

Setting up a queue observer is straightforward. First define your queue, then create an observer that watches it.

Note

When you run raindrop build generate, Raindrop automatically sets up the function code, queue configuration, and all required service bindings for your observer.

raindrop.manifest

// Define the queue
queue "observed-queue" {}

// Create the queue observer
observer "queue-observer" {
  source {
    queue = "observed-queue"
  }
}

index.ts

import { Each } from '@liquidmetal-ai/raindrop-framework';
import { Env } from './raindrop.gen';

export default class extends Each<Body, Env> {
  async process(message: Body): Promise<void> {
    console.log(JSON.stringify(`received message: ${message}`));
  }
}
export interface Body {
}