CODEWITHSUNDEEP
node.jsexpress
Slow Harry
Slow Harry

Reputation: 1897

Fail safe async code with node js

How can I make my node js application fail safe. I wrote the db query wrapper, some provider(to work with user for example, and my controllers(routes))

Function for db connection:

exports.connect = function(callback) {
    sqlClient.connect(function(err, conInfo){
        if (err) callback(err);
        conInfo = 'Connection at ' + sqlClient.host + ':' + sqlClient.port + '/'
            + sqlClient.database + ' used by ' + sqlClient.user;
        callback(null, conInfo);
        //runDDL();
    });
};

Function for query:

exports.runQuery = function(query_str, columns, params, callback) {
    var sqlQuery = query_str + " " + columns;
    var query = sqlClient.query(sqlQuery, params, function(err) {
        if (err) throw err;
        console.log('NEW QUERY____________________');
        console.log(sqlQuery);
        console.log(params);
        if (err) throw err;
        query.on('row', function(row, result) {
            result.addRow(row);
        });
        query.on('end', function (result) {
            callback(null, result.rows);
        });
    });
};

Provider function:

User.prototype.get = function(id, callback) {
db.runQuery('SELECT * FROM users', 'WHERE id=$1', [id],
    function(err, allUsers){
        if (err) throw err;
        callback(null, allUsers[0]);
});

};

Usage in controller:

exports.getById = function(req, res) {
    var id = req.params.user_id;
    userProvider.get(id, function(err, user){
        if (err) throw err;
        res.send(user);
    });
};

In any unexpected situation my server will print error and process will die. How to easier handle some type of errors, for example let's consider that req.params.user_id will be more then number of records in the database.

As you see I just throwing errors with throw err. Is there more fail safe and efficient practice to handle errors, and print to client understandable information, keeping server working?

Upvotes: 0

Views: 498

Answers (1)

Chirag Jain
Chirag Jain

Reputation: 2418

You can write your own error handler with express: Refer example below:

https://github.com/visionmedia/express/blob/master/examples/error/index.js

Upvotes: 2

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