How do I handle errors for fs.createReadStream() in Node.js?

Question

I built a simple server that handled errors (files that aren't found, for example) which works fine:

    fs.readFile(fullPath, function(err, data) {

        // If there is an error, return 404
        if (err) {
            res.writeHead(404);
            res.end();
            debug.log("File denied: " + fullPath);
        } else {
            var length      = data.length;
            var extension   = getExtension(path);
            var type        = getType(extension);

            // If the type doesn't match a MIME type that this app serves, return 404
            if (!type) {
                res.writeHead(404);
                res.end();
                debug.log("File denied: " + fullPath);

            // Otherwise, serve the file
            } else {
                res.writeHead(200, {
                    'Content-Length' : length,
                    'Content-Type' : type
                });
                res.write(data);
                res.end();
                debug.log("File served: " + fullPath);
            }
        }
    });

But I decided that I want to support compression, so I need to use fs.createReadStream() to read the file, like in this example that I'm looking at:

//Check request headers
var acceptEncoding = req.headers['accept-encoding'];
if (!acceptEncoding) {
    acceptEncoding = '';
}

var raw = fs.createReadStream(fullPath);

// Note: this is not a conformant accept-encoding parser.
// See http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.3
if (acceptEncoding.match(/\bdeflate\b/)) {
    response.writeHead(200, { 'content-encoding': 'deflate' });
    raw.pipe(zlib.createDeflate()).pipe(response);
} else if (acceptEncoding.match(/\bgzip\b/)) {
    response.writeHead(200, { 'content-encoding': 'gzip' });
    raw.pipe(zlib.createGzip()).pipe(response);
} else {
    response.writeHead(200, {});
    raw.pipe(response);
}

So my problem is that I'm trying to figure out how to incorporate my error handling into the stream approach since fs.createReadStream() doesn't take a callback function.

How do I handle errors for Node.js fs.createReadStream()?

mscdex · Accepted Answer · 2014-12-24 17:10:34Z

29

Streams can emit an error event. You can listen for this event to prevent the default behavior of throwing the error:

raw.on('error', function(err) {
  // do something with `err`
});

answered Dec 24, 2014 at 17:10

mscdex

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2 Comments

user2076675 Over a year ago

Cool, I was thinking of something like that but didn't see it in the docs.

mscdex Over a year ago

Here is the link to the readable stream error event doc.

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