NodeJS V8 not doing proper garbage collecting

Question

I have this simple http server

var http = require('http');

var server = http.createServer(function(request, response) {

    var data = [];
    for ( var i=0; i < 1000000; i++ ) {
        data.push({});
    }

    response.end('Done');

});

server.listen(3000);

When I start the server the process uses around 8MB of memory. When I make a request to the server the memory usage rises to above 100MB and it just stays like that. Then I hold F5 for a few seconds to spam some requests and the memory usage grows above 400MB at some points. When all the request are processed the server is still using above 100MB.

When I make another request the memory sometimes goes above or close to 200MB or stays approximately the same. I let the server running for a while and the memory doesn't get released.

I tried putting date = null and the result was the same. Then I tried running the server with the --expose-gc flag and putting global.gc() after I null the value and the results are better but the memory still stays above 50MB.

Answer 1

If your system has an abundance of memory available, there is unlikely to be any condition triggering a need for garbage collection. If you can run up the memory usage to a maximum point and continue serving requests, clearly garbage collection is working, as memory will need to be freed before more is allocated.

You can try starting up a different process to deliberately suck up more memory, then look again to see if the original node.js process' garbage collection seems to behave more aggressively.