Given the following node.js + oriento sample code, I have an issue of running into a timeout, [OrientDB.ConnectionError [2]: read ETIMEDOUT], first time I make a DB query after a longish inactivity period. Right after the timeout error the connection is somehow re-initialized and the next query runs fine.
var oriento = require("oriento"),
server = oriento({...}),
db = server.use("users");
var getData = function(statement, opts, callback) {
db.query(statement, opts).then(function(data) {
callback(null, data);
}).catch(callback);
};
So I have the following questions:
Is this the right way to go or should I call oriento({...}).use("users") every time I make a query rather than reusing the connection object?
If this is the right way, why the connection is not validated and refreshed automatically?
How can I manually check that I am not going to run into a timeout (i.e. validate the connection) and force a connection refresh?
Any suggestions better than the following fairly ugly hack to keep the transport socket by pinging the DB every minute?
setInterval(function(db) {
db.query("select from user").then(function(data) {
console.log("still alive");
}).catch(function(err) {
console.error(err);
});
}, 60000, db);
Related
I have an nodejs application that using oracledb module to connect many oracle database. This application is monitoring all databases in one place.
But there is a problem. I am creating a file to connect to oracle db and execute sql's. I am using this file to connect to databases. For example:
let conections = [];
function connectToDb(dbid, connStr){
const oracledb = require('oracledb');
oracledb.outFormat = oracledb.OUT_FORMAT_OBJECT;
oracledb.poolMax = 10;
oracledb.poolMin = 1;
oracledb.createPool(connStr).then((conn) => {
conections[dbid] = dbid;
});
}
function executeSql(dbid, sql, callback){
conections[dbid].getConnection().then(conn => {
conn.execute(qry, params, function(err, rows) {
callback(rows);
});
});
}
connectToDb(1, {......});
connectToDb(2, {......});
connectToDb(3, {......});
executeSql(1, 'select * from ....', function(){...}); //response time 1 sn everthing is okey
executeSql(2, 'select * from ....', function(){...}); //response a long time. Than i am getting queue timeout error
executeSql(3, 'select * from ....', function(){...}); //it not working a while time!!
executeSql(1, 'select * from ....', function(){...}); //it not working a while time!!
//this functions are async. Please assume that there is setInterval function.
in this code, everthing is okey but when an database get NJS-040: connection request timeout. Request exceeded queueTimeout of 60000 error for one database, all databases are effecting by this situation.
I think these connections not isolated and I think that if I can create isolated connections this stuation will be solve. For example can i using import instead of require?
Thank you for your helps
At some point you have to:
await connection.close();
Otherwise you're essentially opening a new connection to the database pool without closing the other connections. I ran into this problem myself re-coding an API.
There is a setting to increase connection request timeout
oracledb.queueTimeout = 3000; // 3 seconds (https://github.com/oracle/node-oracledb/blob/main/doc/api.md#propdbqueuetimeout)
Or you can read more about thread here https://oracle.github.io/node-oracledb/doc/api.html#numberofthreads
export const client = new MongoClient(
process.env.ATLAS_URI,
// TODO: Figure out what this is and why it's needed to turn off deprecation warning
{
useUnifiedTopology: true,
}
);
Following this guide and all make sense...but she is just doing one 'call' and then close().
I need to keep doing repeated calls:
export const getAllProducts = async () => {
try {
await client.connect();
const cursor = await client.db("products").collection("data").find();
return await cursor.toArray();
} catch (err) {
throw new Error(err);
} finally {
await client.close();
}
};
The first call is fine. After that: Error: MongoError: Topology is closed, please connect
I honestly don't quite understand what Topology means, but evidently it's the close() that's contributing to the issue.
It doesn't make sense that I set up new MongoClient and the ATLAS_URI does have the 'database name' in there...so why I have to connect specify that again?
Anyway, the main part of my ❓ stands: Do I just keep a separate process going and not close it? Do I start back with a whole new MongoClient each time? 😕
I'll just put a brief answer here incase anyone runs into this.
The Mongodb documentation for the Node.js driver will give you simple examples that include the client.connect()and client.close() methods just to give you a runnable example of making a simple call to the database but in a real server application you are just opening the connection to the client once during start up and typically only closing when the server application is being closed.
So in short: You don't need to open and close and connection everytime you want to perform some action on your database.
I'm trying to save some json files inside my database using a custom function I've wrote. To achieve that I must connect to the database which I'm trying to do using this piece of code at the start of the function:
let url = "mongodb://localhost:27017/database";
(async () => {
const directory = await fs.promises.readdir(__dirname + '/files')
let database = await mongoose.createConnection(url, {useNewUrlParser:true, useUnifiedTopology:true});
database.on('error', error => {
throw console.log("Couldn't Connect To The Database");
});
database.once('open', function() {
//Saving the data using Schema and save();
Weirdly enough, when executing database.once('open', function()) the callback function isn't being called at all and the program just skips the whole saving part and gets right to the end of the function.
I've searched the web for a solution, and one solution suggested to use mongoose.createConnection instant of mongoose.connect.
As you can see it didn't really fixed the issue and the callback function is still not being called.
How can I fix it, and why it happens?
Thanks!
mongoose.createConnection creates a connection instance and allows you to manage multiple db connections as the documentation states. In your case using connect() should be sufficient (connect will create one default connection which is accessible under mongoose.connection).
By awaiting the connect-promise you don't actually need to listen for the open event, you can simply do:
...
await mongoose.connect(url, {useNewUrlParser:true, useUnifiedTopology:true});
mongoose.model('YourModel', YourModelSchema);
...
I have an amazon beanstalk node app that uses the postgres amazon RDS. To interface node with postgres I use node postgres. Code looks like this:
var pg = require('pg'),
done,client;
function DataObject(config,success,error) {
var PG_CONNECT = "postgres://"+config.username+":"+config.password+"#"+
config.server+":"+config.port+"/"+config.database;
self=this;
pg.connect(PG_CONNECT, function(_error, client, done) {
if(_error){ error();}
else
{
self.client = client;
self.done = done;
success();
}
});
}
DataObject.prototype.add_data = function(data,success,error) {
self=this;
this.client.query('INSERT INTO sample (data) VALUES ($1,$2)',
[data], function(_error, result) {
self.done();
success();
});
};
To use it I create my data object and then call add_data every time new data comes along. Within add_data I call 'this/self.done()' to release the connection back to the pool. Now when I repeatedly make those requests the client.query never gets back. Under what circumstance could this lead to a blocking/not responding database interface?
The way you are using pool is incorrect.
You are asking for a connection from pool in the function DataObject. This function acts as a constructor and is executed once per data object. Thus only one connection is asked for from the pool.
When we call add_data the first time, the query is executed and the connection is returned to the pool. Thus the consequent calls are not successful since the connection is already returned.
You can verify this by logging _error:
DataObject.prototype.add_data = function(data,success,error) {
self=this;
this.client.query('INSERT INTO sample (data) VALUES ($1,$2)',
[data], function(_error, result) {
if(_error) console.log(_error); //log the error to console
self.done();
success();
});
};
There are couple of ways you can do it differently:
Ask for a connection for every query made. Thus you'll need to move the code which ask for pool to function add_data.
Release client after performing all queries. This is a tricky way since calls are made asynchronously, you need to be careful that client is not shared i.e. no new request be made until client.query callback function is done.
In so many introductory examples of using MongoDB, you see code like this:
var MongoClient = require('mongodb').MongoClient;
MongoClient.connect("mongodb://localhost:port/adatabase", function(err, db)
{
/* Some operation... CRUD, etc. */
db.close();
});
If MongoDB is like any other database system, open and close operations are typically expensive time-wise.
So, my question is this: Is it OK to simply do the MongoClient.connect("... once, assign the returned db value to some module global, have various functions in the module do various database-related work (insert documents into collections, update documents, etc. etc.) when they're called by other parts of the application (and thereby re-use that db value), and then, when the application is done, only then do the close.
In other words, open and close are done once - not every time you need to go and do some database-related operation. And you keep re-using that db object that was returned during the initial open\connect, only to dispose of it at the end, with the close, when you're actually done with all your database-related work.
Obviously, since all the I/O is asynch, before the close you'd make sure that the last database operation completed before issuing the close. Seems like this should be OK, but i wanted to double-check just in case I'm missing something as I'm new to MongoDB. Thanks!
Yes, that is fine and typical behavior. start your app, connect to db, do operations against the db for a long time, maybe re-connect if the connection ever dies unexpectedly, and then just never close the connection (just rely on the automatic close that happens when your process dies).
mongodb version ^3.1.8
Initialize the connection as a promise:
const MongoClient = require('mongodb').MongoClient
const uri = 'mongodb://...'
const client = new MongoClient(uri)
const connection = client.connect() // initialized connection
And then call the connection whenever you wish you perform an action on the database:
// if I want to insert into the database...
const connect = connection
connect.then(() => {
const doc = { id: 3 }
const db = client.db('database_name')
const coll = db.collection('collection_name')
coll.insertOne(doc, (err, result) => {
if(err) throw err
})
})
The current accepted answer is correct in that you may keep the same database connection open to perform operations, however, it is missing details on how you can retry to connect if it closes. Below are two ways to automatically reconnect. It's in TypeScript, but it can easily be translated into normal Node.js if you need to.
Method 1: MongoClient Options
The most simple way to allow MongoDB to reconnect is to define a reconnectTries in an options when passing it into MongoClient. Any time a CRUD operation times out, it will use the parameters passed into MongoClient to decide how to retry (reconnect). Setting the option to Number.MAX_VALUE essentially makes it so that it retries forever until it's able to complete the operation. You can check out the driver source code if you want to see what errors will be retried.
class MongoDB {
private db: Db;
constructor() {
this.connectToMongoDB();
}
async connectToMongoDB() {
const options: MongoClientOptions = {
reconnectInterval: 1000,
reconnectTries: Number.MAX_VALUE
};
try {
const client = new MongoClient('uri-goes-here', options);
await client.connect();
this.db = client.db('dbname');
} catch (err) {
console.error(err, 'MongoDB connection failed.');
}
}
async insert(doc: any) {
if (this.db) {
try {
await this.db.collection('collection').insertOne(doc);
} catch (err) {
console.error(err, 'Something went wrong.');
}
}
}
}
Method 2: Try-catch Retry
If you want more granular support on trying to reconnect, you can use a try-catch with a while loop. For example, you may want to log an error when it has to reconnect or you want to do different things based on the type of error. This will also allow you to retry depending on more conditions than just the standard ones included with the driver. The insert method can be changed to the following:
async insert(doc: any) {
if (this.db) {
let isInserted = false;
while (isInserted === false) {
try {
await this.db.collection('collection').insertOne(doc);
isInserted = true;
} catch (err) {
// Add custom error handling if desired
console.error(err, 'Attempting to retry insert.');
try {
await this.connectToMongoDB();
} catch {
// Do something if this fails as well
}
}
}
}
}