Trigger Function - Reference last_execution date / time of trigger

MongoDB Atlas Atlas Triggers & Functions
1

I am trying to write a function for a scheduled trigger that sends all documents from a collection that have been updated since the trigger was last executed. Is there a system variable or somewhere in the context object that would return this timestamp? I’ve searched extensively and found no examples. Another option may be to write the execution time to a collection at the end of the function, then retrieve that date at the beginning of each function call. If anyone has any similar examples, I would appreciate it. My pipeline definition looks like the following. I just want to be able to set start_date=‘trigger last execution date/time’:

const pipeline = [
          {
            $match: {
               "updatedAt": {
                  $gt: start_date
               }
 
            }
      },  {
            "$out": {
               "s3": {
                  "bucket": "bucket_name",
                  "region": "us-west-2",
                  "filename": filename,
                  "format": {
                        "name": "parquet",
                        "maxFileSize": "10GB",
                        "maxRowGroupSize": "100MB"
                  }
               }
            }
      }
   ];

   return events.aggregate(pipeline);
};
2

Was able to get this working with the following solution, tracking each execution time in a collection:

exports = async function () {

   const service = context.services.get("my_federated_db_name");
   const db = service.db("VirtualDatabase0")
   const events = db.collection("VirtualCollection0");

   const current_timestamp = new Date(Date.now()).toISOString();
   const date_str = current_timestamp.split('T')[0];
   //console.log(date_str);
   const epoch_date=new Date().getTime() / 1000;
   const epoch_date_str=epoch_date.toString();

   //generate unique file name including partition
   const filename="customers/file_date=".concat(date_str).concat("/").concat("customers").concat("_").concat(epoch_date_str);
   console.log('filename: ',filename);

   const event_service=context.services.get("change-stream-poc");
   const event_db=event_service.db("trigger_execution");
   const event_collection=event_db.collection("events");

    //retrieve last execution date from collection
   const start_date_array= await event_collection.find({type: "execution"}).sort( { timestamp: -1 } ).limit(1).toArray(); //Works!
   const start_date_str=start_date_array[0].timestamp;
   const start_date=new Date(start_date_str);
   console.log(JSON.stringify(start_date_array[0].timestamp, null, 4));

   const query_results = await events.find({updatedAt: {$gt: start_date}}).toArray();
   console.log('query results: ',JSON.stringify(query_results, null, 4));

  //const start_date = new Date("2023-01-19T00:00:00.0Z");




   const pipeline = [
          {
            $match: {
               "updatedAt": {
                  $gt: start_date
               }

            }
      },  {
            "$out": {
               "s3": {
                  "bucket": "mybucket",
                  "region": "us-west-2",
                  "filename": filename,
                  "format": {
                        "name": "parquet",
                        "maxFileSize": "10GB",
                        "maxRowGroupSize": "100MB"
                  }
               }
            }
      }
   ];

   const response= events.aggregate(pipeline);

   //insert execution timestamp into collection
   event_collection.insertOne( { type: "execution", timestamp: current_timestamp.toString() } );
   return response
};