How to set a Max Execution Time for Each Request Without Sub-Processes

[Eric Fong]

Would like to set a Max Execution Time for Each Request and return the
temp result to the child on time.

How can I do that without create a sub-process?

Can I stop or signal a Script.runInNewContext context that they are
timeout and need to return something?

Is that possible?

Thanks

[Preston Guillory]

var max_execution_time = 30; // seconds

http.createServer(function(request, response) {
    var timeout = setTimeout(function() {
        timeout = null
        response.writeHead(500);
        response.end('Timed out!');
    }, max_execution_time*1000);

    do_some_stuff(function() {
        if (timeout) {
            clearTimeout(timeout);

            response.writeHead(200);
            response.end('Finished in time.');
        }
    });

    function do_some_stuff(callback) {
        // we have 30 seconds to call callback()
    }
}).listen(8000);

[Eric Fong]

Hi

Consider do_some_stuff call db and do some heavy map and reduce
function.
which adding check if (timeout) inside those function is not possible.

When it is timeout, any way to kill the map and reduce operation like
killing a thread or process?

Eric

[Preston Guillory]

There are no threads in Node, but still you have several approaches available here.

1. Run the map/reduce work in a child process, like you said.  If it times out, kill the process.  You'd lose a lot of performance -- starting each process is expensive, and each concurrent request means another process hogging the CPU.  Maybe you can afford the performance hit.  Depends on what you're doing.

2. Sprinkle the map/reduce code with checks, like if (timeout) return.  It's probably the least performance overhead, but it'll sacrifice code cleanliness.  Anyway you said it's impossible in this case.

3. Library-specific controls.  I can imagine a map/reduce library being implemented with pause() and resume() functions.  Wouldn't that be cool?  The downside is I just made it up, so it doesn't exist, as far as I know.  (Would love to be corrected on that.)

I guess that's kind of a limited definition of "several".

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[Preston Guillory]

Does the work you're doing fit in the node.io framework?  It supports timeouts out of the box.