+1 What everyone else said.
However, you MAY still have a race condition here!
```javascript
var outputBuffer = "";
SetInterval(function() {
outputBuffer += "asdf";
}, 100);
websocket.onMessage(function() {
// reply with outputbuffer
send(outputBuffer); // Race condition?
outputBuffer = ""; // What if SetInterval happened?
});
```
Between the two lines in the websocket.onMessage callback, the
setInterval cannot interrupt. However, it's not clear from reading
this code whether the function passed to websocket.onMessage will be
called immediately or at some time in the future. (From the name of
the function, I'd expect it to be at some future time.) So, it may be
called either before or after the setInterval, but *not* in parallel
with it.
Furthermore, actual Buffer objects (unlike your "outputBuffer" string
shown above) *are* subject to break-ins! Consider this code:
```javascript
var fd = fs.openSync("foo.txt", "r")
var buf = new Buffer(fs.statSync("foo.txt").size)
buf.fill(0)
fs.read(fd, 0, buf.length, 0, function () {
throw new Error("This will never be called")
})
while (true) { // loop goes forever, jealously holding onto this tick
for (var i = 0; i < buf.length; i ++) {
// I sure hope there are no break-ins...
if (buf[i] !== 0) {
throw new Error("HIDE YA KIDS, HIDE YA WIFE")
// todo: Hide ya husbands too. They takin e'rbody up in here.
}
}
}
```
In this case, the JavaScript thread is never given up, but
nevertheless, the buffer object (which accesses memory outside of the
V8 heap) is going to be changed in the background by the fs operation
happening in a libuv thread.
The moral of the story is: If you pass a Buffer to a function, it's no
longer your buffer! Reading from it or writing to it at that point is
entering the territory of undefined behavior.
If you exercise care around that one sharp edge, the race conditions
in nodejs are generally pretty easy to manage. Events may come back
in arbitrary order, but they'll always come in single file.
On Thu, Mar 15, 2012 at 11:33, Mark Hahn <[email protected]> wrote:
> That beauty of node is that you *don't* have to worry about concurrency
> issues like that.
>
>
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