function Connect() {
var connection = mysql.createConnection({
host : 'hidden',
user : 'hidden',
password : 'hidden',
database : 'hidden'
});
connection.connect(function(err) {
if (err) {
console.log('Error connecting to Database'.red);
setInterval(Connect, 5000);
connection.end();
}else{
console.log('Connected to Database'.green);
}
});
}
Connect();
I am attempting to make it so my code won't crash if the database loses connection.
It will be connected to a database which is prone to many restarts and updates, meaning that the program will crash upon losing connection.
I tried adding setInterval(Connect, 5000); so it would attempt to reconnect if it loses connection but to no luck.
Can someone help me out where I am going wrong?
Assuming you're using the mysql npm package you can use connection pooling provided by the library:
https://github.com/mysqljs/mysql#pooling-connections
When a previous connection is retrieved from the pool, a ping packet is sent to the server to check if the connection is still good.
It's rather easy to use, instead of using createConnection you can use createPool
var pool = mysql.createPool({
connectionLimit : 2,
host : 'example.org',
user : 'bob',
password : 'secret',
database : 'my_db'
});
And then use the pool to query the database.
It has many additional benefits as well e.g. load balancing connections.
Related
Our DB is hosted in AWS RDS.
Backend is Nodejs, Mysql, ExpressJs
We followed the same as below node-mysql-doc
var mysql = require('mysql');
var pool = mysql.createPool({
connectionLimit : 10,
host : 'example.org',
user : 'bob',
password : 'secret',
database : 'my_db'
});
pool.query('SELECT 1 + 1 AS solution', function (error, results, fields) {
if (error) throw error;
console.log('The solution is: ', results[0].solution);
});
when we hit API to get data, the DB connection touched almost max-connection exceeds
here is the graph of AWS RDS DB Connection
even though we didn't use the APIs again for 2hours, but still the connections are not released.
It got reduced when we restart the node server.
how to release the connection that showed in AWS graph
First of all, I'm a beginner on NodeJS. Well, I'm using a shared hosting to my project and when the database reaches 1 minute of inactivity, NodeJS crashes and disconnects me from MySQL. Since I'm using a shared hosting, I can't edit the idle time on the MySQL config and I'll need to handle it in code.
I'm using module.exports to handle my connection, as shown below. So how can I make an auto-reconnection script to take care of my issue? Thank you.
var mysql = require('mysql');
module.exports =
{
handle: null,
connect: function(call){
this.handle = mysql.createConnection({
host : 'localhost',
user : 'root',
password : '',
database : 'test',
timezone: 'utc',
charset : 'utf8'
});
this.handle.connect(function (err) {
if(err) {
console.log("[MySQL] Connection error: " + err.code);
} else {
console.log("[MySQL] Successfully connected");
}
});
}
};
The node mysql module that you are using also has a connection pooling mechanism.
Check out the docs at https://github.com/mysqljs/mysql#pooling-connections
Connection pools will make you task easier. You can then store the connection pool object and use its getConnection method to obtain a connection. Make sure that you release the connection when you are done with it.
If for some reason you cant use connection pooling then you will have to listen for error event on the connection and handle it accordingly. But I strongly recommend that you use connection pool.
I am trying to connect mysql with nodejs, but there is a problem in my code, please help!
var express = require("express");
var mysql = require('mysql');
var connection = mysql.createConnection({
host : 'localhost',
user : 'root',
password : 'admin',
database : 'dbname',
});
var app = express();
connection.connect(function(err){
if(!err) {
console.log("Database is connected ... \n\n");
} else {
console.log("Error connecting database ... \n\n");
}
});
app.listen(3000);
in terminal i am getting this output:
voldemort#Lenovo:~/Documents/cloudprint$ node server.js
Error connecting database ...
The MySQL client establishes a connection to the server using secure authentication by default.
insecureAuth: Allow connecting to MySQL instances that ask for the old (insecure) authentication method. (Default: false) 1
Looking at the error traceback in your comment, it looks like your server isn't currently configured to allow secure authentication. 2
If your MySQL server version is <= 5.6.4 then secure auth is off and you may want to enable the old auth protocol by enabling insecureAuth when making the connection in the client.
var connection = mysql.createConnection({
host : 'localhost',
user : 'root',
password : 'admin',
database : 'dbname',
insecureAuth: true
});
However, I advise updating the passwords for your users to use the more secure password hashing function if your MySQL server version is >= 5.6.5.
There is step-by-step documentation to accomplish this for user accounts.
You may also want to update your MySQL server if you find that you're running an older version that doesn't support the secure auth protocol.
I'm building an Node application which will query simple and more complex (multiple joins) queries. I'm looking for suggestions on how I should manage the mySQL connections.
I have the following elements:
server.js : Express
router1.js (fictive name) : Express Router middleware
router2.js (fictive name) : Express Router middleware
//this is router1
router.get('/', function (req, res){
connection.connect(function(Err){...});
connection.query('SELECT* FROM table WHERE id = "blah"', function(err,results,fields){
console.log(results);
});
...
connection.end();
})
Should I connect to mysql everytime '/router1/' is requested, like in this example, or it's better to leave one connection open one at start up? As: connection.connect(); outside of: router.get('/',function(req,res){
...
}); ?
I am using mysql2 for this, it is basicly mysql but with promises. If you use mysql you can also do this.
Create a seperate file called connection.js or something.
const mysql = require('mysql2');
const connection = mysql.createPool({
host: "localhost",
user: "",
password: "",
database: ""
// here you can set connection limits and so on
});
module.exports = connection;
Then it is probaly better you create some models and call these from within your controllers, within your router.get('/', (req, res) => {here});
A model would look like this:
const connection = require('../util/connection');
async function getAll() {
const sql = "SELECT * FROM tableName";
const [rows] = await connection.promise().query(sql);
return rows;
}
exports.getAll = getAll;
You can do this with or without promises, it doesn't matter.
Your connection to the pool is automatically released when the query is finished.
Then you should call getAll from your router or app.
I hope this helped, sorry if not.
Connection pooling is how it should be done. Opening a new connection for every request slows down the application and it can sooner or later become a bottleneck, as node does not automatically closes the connections unlike PHP. Thus connection pool ensures that a fixed number of connections are always available and it handles the closing of unnecessary connections as and when required.
This is how I start my express app using Sequelize. For Mongoose, it is more or less simlar except the library API.
const sequelize = new Sequelize('database', 'username', 'password', {
host: 'localhost',
dialect: 'mysql',
pool: {
max: 5,
min: 0,
acquire: 30000,
idle: 10000
}
});
sequelize.authenticate()
.then(
// On successfull connection, open a port
// and listen to requests. This is where the application
// starts listening to requests.
() => {
const server = http.createServer(app);
server.listen(port);
},
)
.catch(err => {
console.error('Unable to connect to the database:', err);
console.error('Cancelling app server launch');
});
The app is started only after a database connection has been established. This ensures that the server won't be active without any database connection. Connection pool will keep the connections open by default, and use a connection out of the pool for all queries.
If you use createPool mysql will manage opening and closing connections and you will have better performance. It doesn't matter if you use mysql or mysql2 or sequlize. use a separate file for createPool and export it. You can use it everywhere. Don't use classes and just do it functionally for better performance in nodejs.
> npm install mysql
mysql is a great module which makes working with MySQL very easy and it provides all the capabilities you might need.
Once you have mysql installed, all you have to do to connect to your database is
var mysql = require('mysql')
var conn = mysql.createConnection({
host: 'localhost',
user: 'username',
password: 'password',
database: 'database'
})
conn.connect(function(err) {
if (err) throw err
console.log('connected')
})
Now you are ready to begin writing and reading from your database.
when I use node mysql, an error is appear between 12:00 to 2:00 that the TCP connection is shutdown by the server. This is the full message:
Error: Connection lost: The server closed the connection.
at Protocol.end (/opt/node-v0.10.20-linux-x64/IM/node_modules/mysql/lib/protocol/Protocol.js:73:13)
at Socket.onend (stream.js:79:10)
at Socket.EventEmitter.emit (events.js:117:20)
at _stream_readable.js:920:16
at process._tickCallback (node.js:415:13)
There is the solution. However, after I try by this way, the problem also appear. now I do not know how to do. Does anyone meet this problem?
Here is the way I wrote follow the solution:
var handleKFDisconnect = function() {
kfdb.on('error', function(err) {
if (!err.fatal) {
return;
}
if (err.code !== 'PROTOCOL_CONNECTION_LOST') {
console.log("PROTOCOL_CONNECTION_LOST");
throw err;
}
log.error("The database is error:" + err.stack);
kfdb = mysql.createConnection(kf_config);
console.log("kfid");
console.log(kfdb);
handleKFDisconnect();
});
};
handleKFDisconnect();
Try to use this code to handle server disconnect:
var db_config = {
host: 'localhost',
user: 'root',
password: '',
database: 'example'
};
var connection;
function handleDisconnect() {
connection = mysql.createConnection(db_config); // Recreate the connection, since
// the old one cannot be reused.
connection.connect(function(err) { // The server is either down
if(err) { // or restarting (takes a while sometimes).
console.log('error when connecting to db:', err);
setTimeout(handleDisconnect, 2000); // We introduce a delay before attempting to reconnect,
} // to avoid a hot loop, and to allow our node script to
}); // process asynchronous requests in the meantime.
// If you're also serving http, display a 503 error.
connection.on('error', function(err) {
console.log('db error', err);
if(err.code === 'PROTOCOL_CONNECTION_LOST') { // Connection to the MySQL server is usually
handleDisconnect(); // lost due to either server restart, or a
} else { // connnection idle timeout (the wait_timeout
throw err; // server variable configures this)
}
});
}
handleDisconnect();
In your code i am missing the parts after connection = mysql.createConnection(db_config);
I do not recall my original use case for this mechanism. Nowadays, I cannot think of any valid use case.
Your client should be able to detect when the connection is lost and allow you to re-create the connection. If it important that part of program logic is executed using the same connection, then use transactions.
tl;dr; Do not use this method.
A pragmatic solution is to force MySQL to keep the connection alive:
setInterval(function () {
db.query('SELECT 1');
}, 5000);
I prefer this solution to connection pool and handling disconnect because it does not require to structure your code in a way thats aware of connection presence. Making a query every 5 seconds ensures that the connection will remain alive and PROTOCOL_CONNECTION_LOST does not occur.
Furthermore, this method ensures that you are keeping the same connection alive, as opposed to re-connecting. This is important. Consider what would happen if your script relied on LAST_INSERT_ID() and mysql connection have been reset without you being aware about it?
However, this only ensures that connection time out (wait_timeout and interactive_timeout) does not occur. It will fail, as expected, in all others scenarios. Therefore, make sure to handle other errors.
better solution is to use the pool - it will handle this for you.
const pool = mysql.createPool({
host: 'localhost',
user: '--',
database: '---',
password: '----'
});
// ... later
pool.query('select 1 + 1', (err, rows) => { /* */ });
https://github.com/sidorares/node-mysql2/issues/836
To simulate a dropped connection try
connection.destroy();
More information here: https://github.com/felixge/node-mysql/blob/master/Readme.md#terminating-connections
Creating and destroying the connections in each query maybe complicated, i had some headaches with a server migration when i decided to install MariaDB instead MySQL. For some reason in the file etc/my.cnf the parameter wait_timeout had a default value of 10 sec (it causes that the persistence can't be implemented). Then, the solution was set it in 28800, that's 8 hours. Well, i hope help somebody with this "güevonada"... excuse me for my bad english.