Blue Flower

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Category: Node JS
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Express application allows to open only one database connection pool object across the application. 

In this example,

1/ mssql library is used to connect MS-SQL server

2/ one time connection pool is generated in the library file "commonDbConnection.js"

3/ above library is referred where ever its required.  In our example, used it in "server.js" & "anotherlibraryfile.js"

config.js

var config = {
 databaseConn: {
 server: "dbserver",
 database: "db",
 user: "uid",
 password: "pwd",
 options: {
 encrypt: false
 }
 },

Config_Key1: 'config_value1',

Config_Key2: 'config_value2',

Config_Obj: {
  config_key3 : 'config_value3',
  config_key4 : 'config_value4',
  config_key5 : 'config_value5',
}

};

module.exports = config ;

commonDbConnection.js

It returns as a promise object "commonConnPool"

var config = require("./config").databaseConn;

const mssql = require("mssql");

const commonConnPool = new mssql.ConnectionPool(config)
 .connect()
 .then(pool => {
 console.log("Connected to MSSQL");
 return pool;
 })
 .catch(err => console.log("Database Connection Failed! Bad Config: ", err));

module.exports = {
 mssql,
 commonConnPool
};

server.js

....

var commonConnPool= require('./commonDbConnection').commonConnPool;

(or)

var {commonConnPool} = require('./commonDbConnection')

....

//While setup CORS inject the DB connection pool and later you can retrieve it in the API library


app.use(async function (req, res, next) {
 res.header("Access-Control-Allow-Origin", "*");
 res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
 req.conn_pool = await commonConnectionPool;
 next();
});

...

app.use('/api', api);

 

anotherlibraryfile.js

 

var { commonConnPool, mssql } = require('./dbInitCommonConn');

async insertIntoDB(value1, value2, value3) {
 try {

await commonConnPool.then(pool => {
 pool
 .request()
 .input("param1", mssql.VarChar(50), value1)
 .input("param2", mssql.VarChar(50), value2)
 .input("param3", mssql.VarChar(50), JSON.stringify(value3)) //if its object, then stringify it before pass
 JSON.stringify(message)
 )
 .execute("usp_Insert_Record_SP");
 });
 } catch (err) {
 console.log("error occurred", err);
 }
 }

 

 

 

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Details
Category: Node JS
Hits: 5151

Step 1 : Eject

npm run eject

This command used to moves create-react-app's  configuration files and dev/build/<<appname>> scripts into you <<app>> directory.

Note:

To run this command make sure following topics

  • Add any untracked files you want to keep to your Git repository.
  • Remove any untracked files you don't want to keep (either by deleting them or adding them to your .gitignore)
  • Commit your changes, or stash them if you'd like to commit them at a later time
  • create-react-app prevents you from ejecting your app without first having committed any outstanding changes to Git


Step 2: babel's remove-console

Install babel-plugin-transform-remove-console library and make following changes in package.json configuration file

 

npm install babel-plugin-transform-remove-console


"babel": {
 "presets": [
 "react-app"
 ],
 "plugins": [
 "transform-remove-console"
 ]
 }

Step 3: Build ReactJS

Run following command to build ReactJS application to deploy on production.  It will place all the files under a folder "build"

npm run build

 

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Details
Category: Node JS
Hits: 5360

PM2 is straightforward, it is offered as a simple and intuitive CLI, installable via NPM. Just start your application with PM2 to boost your application and to make it ready to handle a ton of traffic!

Installation

The latest PM2 stable version is installable via NPM:

npm install pm2@latest -g

Above will install the latest version and if its running then you need update the in-memory version by running following command

pm2 update

Usage

The simplest way to start, daemonize and monitor your application is by using this command line:

pm2 start app.js

Application declaration

You can also create a configuration file to manage multiple applications:

process.yml:

apps:
  - script   : app.js
    instances: 4
    exec_mode: cluster
  - script : worker.js
    watch  : true
    env    :
      NODE_ENV: development
    env_production:
      NODE_ENV: production

And start it easily:

pm2 start process.yml

Read more about application declaration here.

Setup startup script

Restarting PM2 with the processes you manage on server boot/reboot is critical. To solve this, just run this command to generate an active startup script:

pm2 startup


Stop PM2 process

pm2 kill

Stop an instance running under PM2

pm2 stop <<instance_id>>

pm2 stop 0


If you want to stop all running instances

pm2 stop all

Cluster setup

pm2 start server.js -i max

"max" is deprecated and instead of that you can supply 0  pm2 start server.js -i 0

This will roll out maximum number of instance based on no of core available in the server

Supply parameter while initiate an instance

pm2 start server.js -- DEV

In above example, DEV is the parameter value supplied

pm2 start -i 0 server.js -- PARAM1 PARAM2

Above one roll out maximum no of instances based of no of core available and supplying PARAM1 & PARAM2

To display logs (especially the startup logs which includes console.log in express application)

pm2 logs startup

To see metrics & detail of a particular running instance

pm2 show <<instance_id>>

To monitor all running instance with metrics & meta details

pm2 monit
pm2 show 0

To see all environment variable available for the particular instance

pm2 env <<instance_id>>
pm2 env 0
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