functions-samples/lastmodified-tracking

Tracking last modified Date of a Firebase Database

This template shows how to keep track of the date at which the Firebase Database or a subset of a firebase Database was last modified.

Cloud Function Code

See file index.js for the code.

This is done by simply updating a lastmodified attribute on the parent of the node which is tracked (for instance at the root of the Database).

The dependencies are listed in package.json.

Sample Database Structure

As an example we'll be using a simple chat database structure:

/functions-project-12345
    /chat
        /key-123456
            username: "Mat"
            text: "Hey Bob!"
        /key-123457
            username: "Bob"
            text: "Hey Mat"

Trigger rules

Below is the trigger rule for the touch function making sure it's triggered when a new chat message is added/modified.

  "functions": {
    ".source": "functions",
    "touch": {
      "triggers": {
        "database": {
          "path": "/chat/$message",
        }
      }
    }
  }

Security Rules

The following security rules ensures only a Cloud Function with admin access can update the lastmodified attribute.

{
  "rules": {
    "lastmodified": {
        ".write": "false", // TODO: Check that this works with GCF admin access!
        ".read": "true"
    }
  }
}