Maximum call stack size exceeded

[gilly3]

While load testing my app, I am seeing RangeError: Maximum call stack size exceeded, with promise-redis in the stack trace. Asking here is a bit of a stab in the dark, but I thought I'd check. Here are a couple of suspicious looking stack traces:

I have to process several thousand requests before I start seeing this error. It looks like the promisify function is calling itself recursively. Any idea what might be causing this?

[gilly3]

FYI: I was able to resolve this by writing my own promise wrapper that has no chance of recursive function calls. I'm no longer using promise-redis and the errors are gone.

[mdjaman]

@gilly3 Can you share your code please

[maxbrieiev]

Hi!

Sorry for late reply. promise-redis doesn't do any recursive calls.

What node_redis version is used here? Is it possible to create a reproducible example? If not, could you share parts of code that cause this error.

Thanks.

[gilly3]

I had tried to boil this down to a small example, but was unable to do so. Any attempts at isolating the problem were unable to reproduce the error. Running all of my code, I was only ever able to reproduce this while under extreme load for several minutes.

The stack trace led me to line 35, which is f.apply(this, args) within promisify():

if (typeof args[args.length - 1] === 'function') {
    // Okay. Someone supplied a callback. Most likely some internal
    // node-redis call (ready probe etc.). Oh, as a result of
    // supporting internal callback-style calls, one can now use
    // promise-redis as a dropin replacement for node-redis.
    f.apply(this, args);
}

The recursion could occur if a promisified function is being passed as a parameter, thus being repromisified. My code isn't doing this, as I use promises instead of callbacks. I stopped digging and just wrote my own promisifier for the few redis calls that I need.

I was using only GET, SET, PUBLISH, and SUBSCRIBE commands. I've since abandoned PUBLISH and SUBSCRIBE, so to promisify my calls now, it's something like this:

function get(key) {
    return new Promise((resolve, reject) =>
        client.get(key, (err, data) => err ? reject(err) : resolve(data)));
}
function set(key, val, expire) {
    return new Promise((resolve, reject) =>
        client.set(key, val, "EX", expire, (err, data) => err ? reject(err) : resolve(data)));
}

[maxbrieiev]

Thanks for your reply.

"promisification" happens only once, when promise-redis is initialized. Each redis command is replaced with the function returned from promisify function.

From the stack trace it looks that it is internal_send_command that passes a callback to promisified set command. But it is hard to tell what happens in the originating code, because line 877 from the latest node_redis git repo doesn't point to any function call.