Tips for receiving alerts on external updates to a mongo collection using sails

Currently, I am in the process of creating an application utilizing mongo and sails. As part of my development, I am investigating how the real-time update feature in sails functions.

Although I am currently using sails 0.9.16, I am also curious about answers pertaining to sails 0.10.

My goal is to have a list automatically updated whenever new documents are added to the corresponding collection. This functionality works smoothly when I insert documents using sails sockets by sending a post message. In this scenario, I can observe other clients receiving notifications and the list on their end being refreshed.

The challenge arises from an external service that writes directly to the mongo database, causing the collection to continuously grow. Unfortunately, any new elements created through the external service are not being notified to listening clients. As a result, users must manually refresh the web page to view these new elements.

In light of this situation, I have some questions:

  • Is it expected for notifications regarding database creations to function even if they originate outside of sails?
  • If so, does this necessitate specific configurations to be implemented?
  • If not, what would be a recommended approach to maintain an up-to-date client-side listing of a collection with ongoing changes to the database?

Cheers!

javascriptmongodbsails.js

Answer №1

This question is quite intriguing, although it's not uncommon: the developers at Meteor faced a similar challenge. Without monitoring the database, scaling your application horizontally becomes difficult because one server process won't be aware of data changes made by another.

Initially, they tried a temporary solution by polling the DB every 10 seconds. However, they eventually implemented a better approach (which could also be applicable to Sails): they now follow the MongoDB oplog and trigger an update whenever there's a change in the relevant collection.

To address your specific queries:

  • As far as I know, a Sails process isn't informed about external changes to the DB;
  • No specific configurations are needed;
  • One way to monitor external DB (MongoDB) updates is by using an npm oplog watcher like this or any other from these, etc.), which detects changes and triggers updates accordingly.

While there isn't a plug-and-play solution available, I hope this gives you a good starting point on how to address the issue.

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