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).

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"
    }
  }
}