How to measure execution time of javascript code with callbacks


Question

I have a piece of javascript code that I am executing using the node.js interpreter.

for(var i = 1; i < LIMIT; i++){
    db.users.save({id : i, name : "MongoUser [" + i + "]"}, function(err, saved) {
          if( err || !saved ) console.log("Error");
          else console.log("Saved");
    });
}

I want to know how to measure the time taken by these db insert operations. I could compute the difference of Date values after and before this piece of code but that would be incorrect because of the asynchronous nature of the code.

1
290
5/16/2012 10:55:35 AM

Accepted Answer

Use the Node.js console.time() and console.timeEnd():

var i;
console.time("dbsave");

for(i = 1; i < LIMIT; i++){
    db.users.save({id : i, name : "MongoUser [" + i + "]"}, end);
}

end = function(err, saved) {
    console.log(( err || !saved )?"Error":"Saved");
    if(--i === 1){console.timeEnd("dbsave");}
};
657
11/4/2014 6:46:50 PM

There is a method that is designed for this. Check out process.hrtime(); .

So, I basically put this at the top of my app.

var start = process.hrtime();

var elapsed_time = function(note){
    var precision = 3; // 3 decimal places
    var elapsed = process.hrtime(start)[1] / 1000000; // divide by a million to get nano to milli
    console.log(process.hrtime(start)[0] + " s, " + elapsed.toFixed(precision) + " ms - " + note); // print message + time
    start = process.hrtime(); // reset the timer
}

Then I use it to see how long functions take. Here's a basic example that prints the contents of a text file called "output.txt":

var debug = true;
http.createServer(function(request, response) {

    if(debug) console.log("----------------------------------");
    if(debug) elapsed_time("recieved request");

    var send_html = function(err, contents) {
        if(debug) elapsed_time("start send_html()");
        response.writeHead(200, {'Content-Type': 'text/html' } );
        response.end(contents);
        if(debug) elapsed_time("end send_html()");
    }

    if(debug) elapsed_time("start readFile()");
    fs.readFile('output.txt', send_html);
    if(debug) elapsed_time("end readFile()");

}).listen(8080);

Here's a quick test you can run in a terminal (BASH shell):

for i in {1..100}; do echo $i; curl http://localhost:8080/; done

Licensed under: CC-BY-SA with attribution
Not affiliated with: Stack Overflow
Icon