Catch exception in node.js

Question

I have a simple program, which needs to make sure I can connect to a Redis server. I use node-redis to connect and need to wait until Redis is started. I use this piece of code:

function initializeRedis(callback) {
    (function createClient(){
        var runner;
        try {
            client = redis.createClient();
        } catch (e) {
            setTimeout(createClient, 1000);
        }
        callback();
    })();
};

initializeRedis(function() {
// Work here
});

This is because without the try/catch, I got an exception from node.js:

 node.js:134
         throw e; // process.nextTick error, or 'error' event on first tick
         ^ Error: Redis connection to 127.0.0.1:6379 failed - ECONNREFUSED, Connection refused
     at Socket.<anonymous> (/var/www/php-jobs/node_modules/redis/index.js:88:28)
     at Socket.emit (events.js:64:17)
     at Array.<anonymous> (net.js:830:27)
     at EventEmitter._tickCallback (node.js:126:26)

When I start redis-server (Ubuntu machine) and start this script, everything works fine. If I stop redis-server and start the script, it doesn't catch the exception and still throws this same exception. How is that possible? I have a try/catch statement!

thejh · Accepted Answer · 2011-11-09 20:43:45Z

12

After client = redis.createClient();, set a handler for the error event:

client.on('error', function(err) {
  // handle async errors here
});

Have a look at the stack trace - your code isn't in it, so there's no place where a try/catch could catch the error.

answered Nov 9, 2011 at 20:43

thejh

45.7k18 gold badges100 silver badges109 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Jurian Sluiman Over a year ago

If the error is asynchronous, how would I be able to wait until I have a valid connection? The problem in my startup cycle is this node script is started with upstart and redis with init.d. Apparently, node starts earlier and I have to wait until redis is ready too. That's what I am trying with the setTimeout() and callback here.

thejh Over a year ago

@JurianSluiman: You don't wait for it, you listen for it. And don't use setTimeout for this kind of stuff, it makes kittens DIE!

Jurian Sluiman Over a year ago

obviously the setTimeout() won't work with this client.on('error') handler, but the problem is I need to WAIT before I can continue because I DEPEND on the client. The callback() is triggered now because no exception is thrown and AFTER that I probably get this error triggered. Aynchronously processing errors sucks because if you depend on the result, you can't really do anything about that?

thejh Over a year ago

@JurianSluiman: huh, what? I don't get what you're trying to say.

Jurian Sluiman Over a year ago

TL;DR: I cannot just "wait" asynchronously for the error because I synchrously depend on the client. Your callback handle is therefore no solution. See my question about the waiting part here: stackoverflow.com/questions/7786660/…

|

Collectives™ on Stack Overflow

Catch exception in node.js

1 Answer 1

6 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related