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[Intro Music]

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We have just successfully created

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a small Express web server

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application using Node.js, and

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we have executed this application.

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And before that we have installed

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some additional packages, namely

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express package along with its

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dependencies using 'npm install'

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command. And all of that we have

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performed inside of the Node.js

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container. There was no NPM, or

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Node running on our local computer.

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But now there is a challenge for

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us, and you see that our

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application is not terminated when

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we press key combination Ctrl+C.

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And when SIGINT signal is sent to our

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Node.js process, it is sent

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directly to our process. And notice

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that in this command, we have

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actually overridden default command,

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this node command, using custom

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command, and we run index.js file

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using Node interpreter. And we have

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also mapped port of our Express

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application, and we have exposed it

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to external port 3000. And we have

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also used the customer working

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directory, and we have mapped our local

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folder using this option. And we

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have mapped this folder to 'app'

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folder inside of the container.

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Great. Let's now modify a bit our

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application, and let's add handling

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of the SIGINT signal. I want to

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show you that because it is

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important for understanding of how

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we're actually connected to node

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process using Docker. Let's go to

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our tiny application here, and

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let's open up index.js file

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located in the 'express' folder. Let

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me hide this left pane. And let's

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add additional package here, and

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it is actually default package Node.js

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package called 'process'. And

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afterwards, we will use this

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package for handling of the SIGINT

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signal. Let's do that. Let's

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require additional package 'const

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process = require('process')', like so.

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And next, for example, here let's

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add following lines, 'process.on()'

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And here first argument will

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be 'SIGINT', and second will be

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callback function, I'll use arrow

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function expression syntax. Again,

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if you don't know Node.js syntax, and

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don't know JavaScript, please

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nevermind, I want to just show you

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how you're able to handle SIGINT

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signal inside of the process inside

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of the container. Okay, let's add

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here arrow function syntax like so.

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And here inside of this arrow

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function, let's do following.

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Let's print to the terminal message

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'Application is being terminated

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...', like so. And here on the

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next line, let's exit from the

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process using the following syntax,

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'process.exit'(), and here let's

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call the method of this process,

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and here let's pass single argument

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0. And it will mean that this

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process will terminate correctly

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with exit code 0. Let's add one

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more line break here like so. And

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that's actually all that we need to

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modify in our application in order

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to handle SIGINT signal. Let's

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save this file. Let's go to our

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terminal. And actually, we need to

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stop this container first, and

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afterwards rerun it over. Let's go

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here, and let's list containers,

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'docker ps'. And now let's use 'docker

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kill' command in order to quickly

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terminate process inside of the

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container because our application

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does not react to SIGTERM command

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as well. Let's enter 'docker kill',

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and here will be '1b', and

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container was terminated. Let's go

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back to this step, and let's rerun our

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application using same command. And

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of course now our changes made in

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this file will be taken into

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account and our application should

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now react to this signal. Actually,

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let me replace 'terminated' with

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'interrupted' here, because we

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actually interrupt our process.

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Let's go back to this step and

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let's rerun this command, and now

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let's press Ctrl+C, and now our

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process was terminated and I see text,

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'Application is being terminated...'.

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Basically, it seems that I have

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not saved the file. Yes, that is the case. Let's save it,

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and also let's add the handling of

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the SIGTERM signal into our

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application as well. Let me copy

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this block, paste here, and here will

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be SIGTERM, and with those lines

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in place, we will be able also to

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use 'docker stop' command that will

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quickly stop corresponding process

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inside of the container. And here

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let's type, 'Application is being

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terminated....', like so. Let's save

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this, and let's now go back to our

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application here. Let's clear

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terminal and let's rerun our

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application, 'CTRL+C'. I see,

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'Application is being interrupted...'

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And now process was terminated of

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course and there are no containers

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currently running. 'docker ps', and

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yes, that's the case. Let's rerun our

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container once again, this actually

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brand new container. And now let's

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go to this step 'docker ps', and

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let's now use 'docker stop' command

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in order to send SIGTERM signal

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to our Node.js process, 'docker

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stop'. And here let's use first

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few characters of CONTAINER ID, 'c1';

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and now container was stopped

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pretty quickly. And that's because

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we have added handling of SIGTERM

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signal to our application. That's

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all for this lecture where I have

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demonstrated you how you're able to

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add handling of the SIGINT and the

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SIGTERM signals to your

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application. And again, we are

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required to do so because we have

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connected directly to Node.js

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process after entering such kind

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of command 'node index.js', we lauched

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a specific file using Node

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interpreter and that's why we

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connect directly to Node.js

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process. And actually, I have proved

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using those lines of code that when

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you press Ctrl+C, Docker sends SIGINT

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signal to corresponding process

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and if you use 'docker stop' command,

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Docker sends SIGTERM signal to

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corresponding process. That's all

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for this lecture. I hope that you

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enjoyed it. And next you will get a

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small challenge and you will need

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to create tiny Node.js application

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yourself. I'll see you next. Bye-Bye.

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[no audio]