Should I worry about cleaning up large objects in Node.js or leaving it to the garbage collector?

Question

I recently ran into a problem with the node.js API, where my memory got bigger and bigger with every request. I host my server on Heroku using their free version, which is only 512 MB of RAM. After getting a lot of traffic over the weekend, I started getting memory errors from Heroku, so I started looking for a memory leak in my code to no avail. I did not hold around any objects, everything had to be cleaned and, frankly, I was lost.

However, after doing some research, I found that node.js starts the garbage collector when it reaches the max-old-space-size variable and the default is 1024 MB on 64-bit systems. I set this to 410 (80% of my available memmory), but wondering if I should just handle this in code? Obviously, it would be ideal to update my copy and just have a standard default cover, but now this is not an option.

Example:

// lets assume there is some apiGet function
// that calls back with a very very large object with
// the following structure:
// {
//      status: "success",
//      statusCode: 200,
//      messages: [],
//      data: { users: [ huge array of users ] }
// }
// we have a manipulateData function that going
// to do some stuff to the returned data and the
// call some callback to give the data to the caller
function manipulateData(callback) {
    apiGet(function(error, veryLargeObject) {
        var users = veryLargeObject.data.users;
        var usefulUsers = users.map(function(user) {
            // do some data calculations here and then
            // return just those properties we needed
        });

        callback(null, usefulUsers)
    });
}

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Answer 1

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Answer 2

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function createClosure(bigData) {
    var unrelatedVar = 1;

    doSomethingAsync(function theCallback(err, result) {
        if (bigData.matches(result)) {
            ...
        }
    });

    return function theReturnedFunction() {
        return unrelatedVar++;
    };
}

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