如何创建匹配嵌套消息属性的 SNS 过滤策略？

Question

I've created an SNS topic, and I'd like to subscribe to it with a filter policy that matches a nested attribute. For example, given a message like this:

{
  "foo": {
    "bar": "baz"
  },
  "quux": "vorp"
}

I'd like to match only messages where the bar attribute of foo is equal to baz .

The documentation I've found so far only mentions matching attributes specified at the top level. I'm interested in a nested attribute. For the purposes of this question, let's assume I don't control the structure of the message.

Answer 1

Subscription filters don't act on the message (body, payload). They only act on the message attributes .

Message attributes are not complex objects... their only types are string, string array, number, and binary. If a message attribute contains a serialized object (eg JSON), subscription filters aren't designed to support extracting/matching the serialized data inside.

Answer 2

As of 2022, it's possible to filter based on the payload.

That's mentioned here: https://docs.aws.amazon.com/sns/latest/dg/sns-message-filtering.html

An Example of filtering:

Let's say your original message is like:

{
  "eventType": "SOME_STRING",
  "otherAttribs": "bla..."
}

Then the filter can be something like:

{
  "eventType": [
    {
      "prefix": "SAMETH"
    }
  ]
}

In AWS WebConsole, it's found in SNS -> Subscriptions -> [select one] -> Subscription filter policy.

Answer 3

Now, SNS can filter events based on their payload as well. With this release, the SNS filter policy can handle property nesting too. For more information, please take a look at: https://aws.amazon.com/blogs/compute/introducing-payload-based-message-filtering-for-amazon-sns/