S3存储桶对象更新/变更时的通知方案咨询（Lambda、SNS）

Absolutely, you can totally set up notifications for S3 object updates and changes using either Lambda directly or SNS—let’s break down both approaches, building on the object creation trigger you already have working:

Option 1: Extend Your Existing Lambda Trigger #

This is the simplest path if you want to reuse your current Lambda setup. S3 lets you specify multiple event types for a single trigger, so you just need to expand the events it listens for:

• Head to your S3 bucket’s Properties tab, then go to Event notifications
• Edit your existing Lambda trigger (or make a new one if you want separate logic for updates vs. creates)
• Under Event types, check the boxes that match your definition of "changes":
  • For object overwrites/updates: s3:ObjectCreated:Put (since overwriting an existing object counts as a Put operation) and s3:ObjectCopy
  • For other types of changes: s3:ObjectTagging:* (if tag updates matter to you), s3:ObjectRestore:*, or s3:ObjectRemoved:* (if deletions count as "changes" for your use case)
• Save your changes. Then, update your Lambda code to handle these new event types—you can check the eventName field in the Lambda event payload to tell the difference between a create, update, delete, etc.

Pro tip: If you have versioning enabled on your bucket, you can also check the versionId in the event payload to distinguish between a brand-new object and an overwrite of an existing one.

Option 2: Use SNS as a Middleman #

SNS is perfect if you need to send these change notifications to multiple targets (like a Lambda function, email alerts, SMS, or other services) instead of just one Lambda. Here’s how to set it up:

1. Create an SNS topic (standard or FIFO, depending on whether you need message ordering)
2. In your S3 bucket’s Event notifications, create a new notification that sends events to this SNS topic
3. Select the same event types as listed above (updates, changes, etc.)
4. Subscribe your Lambda function (or email addresses, other endpoints) to the SNS topic
5. Now, whenever an S3 object is updated or changed, S3 sends the event to your SNS topic, which forwards it to all subscribed endpoints. This is ideal for scaling out notifications to multiple systems or stakeholders.

Key Permissions Notes #

Don’t forget to double-check IAM permissions to avoid delivery issues:

• For Lambda triggers: Ensure S3 has the lambda:InvokeFunction permission to call your Lambda
• For SNS: Make sure S3 has the sns:Publish permission for your topic, and your subscribers have permission to receive messages from the topic

Testing Tip #

Validate your setup by:

• Overwriting an existing object
• Adding/removing tags from an object
• Deleting an object (if you included that event type)
  Then check Lambda logs or SNS delivery status to confirm notifications are firing as expected.

内容的提问来源于stack exchange，提问作者nad87563