On Aug 20, 2014, at 9:26 AM, Дмитрий Папка <[email protected]> wrote:
> Hello, everyone!
> I am new to Node.Js and not very well understanding the mecanics of callbacks.
>
[snip]
> if (long) {
> while (Date.now() < then) {}
> }
> db.users.find({}, function(err, users) {
> callback(users);
> });
[snip]
> If I am openning: http://website.com/, it loads immediately.
> If I am oppening: http://website.com/?long=something, it loads after ~ 5
> seconds as expected.
> Now. If I am openning http://website.com/?long=something and right after that
> http://website.com/ - they both are loading 5 seconds (second request is
> waiting until the first one will end).
> That means I am doing something wrong, because requests are handled not
> asyncroniously.
> What did I do wrong?
The while loop is blocking -- it spins, doing useless work and NOTHING else
until it expires. Your entire node process is hung during this time, so both
requests "wait".
Delaying with:
setTimeout(function() {
db.users.find({}, function(err, users) {
callback(users);
});
}, long ? 5000 : 0);
would do what you want, and yield the event loop in the mean time.
Node only does one thing at a time -- setTimeout is "call me when this time has
passed; do what you need to until then"; while (stuff) is "do nothing but this
until...."
Aria
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