React SSR subscription on server memory leak?

I’m using react-router-ssr to achieve server side rendering and quick initial page loads which is fantastic. On my production server I can see that free memory is reducing slowly over a period of weeks, but that could be due to a slowly increasing user base, and/or a memory leak.

Some of my routes include reactive data using Meteor.subscribe() and collection.find(). This works just as well on the server as the client, which is great - the initial page render is preloaded with the data.

My question is: is the sever-side subscription automatically stopped once the server has finished rendering the page, or is the subscription left open leaking memory (in either Meteor, or MongoDB which is on the same server)?

During the SSR, I can see that componentWillMount is called (which is where I’m subscribing to the data), but componentWillUnmount isn’t, so if the subscription isn’t stopped automatically, where do I stop it?