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‫Okay, so let's go ahead

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‫and create a Lambda function that is going to be integrated

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‫with our load balancer.

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‫So for this I'm going to create a Lambda function,

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‫call it Lambda-alb,

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‫and for the runtime I will choose Python version three,

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‫and then I will just click on create function.

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‫Now, in the meantime,

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‫I also have to create a load balancer

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‫for my Lambda function.

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‫So therefore, let's go ahead and create a load balancer,

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‫and we'll choose an application, load balancer.

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‫Let's go through the create process,

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‫so I'll call this one demo-Lambda-alb.

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‫It's internet facing of IPv4.

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‫I'm going to deploy this in three availability zones,

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‫and for security group,

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‫I'm going to just create a new security group

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‫for my ALB,

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‫just to make sure I have one.

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‫So DemoLambdaALBSG.

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‫And for the inbound rule,

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‫I'm going to just allow HTTP,

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‫coming from anywhere IPv4.

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‫Let's create the security group.

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‫Perfect,

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‫and let's assign this security group

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‫into our load balancer.

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‫Okay, next we allow to listen

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‫on port 80 for the HTTP protocol.

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‫And the default action is to send to a target group,

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‫so we have to create a target group

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‫that will contain our Lambda function.

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‫So therefore, when we create this target group,

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‫we're going to choose Lambda function,

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‫and this one will be demo-tg-lambda.

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‫And this target group is accessible

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‫to application load balancers only.

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‫So let's go ahead and click on next.

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‫Next, we need to choose a Lambda function,

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‫so we'll choose the Lambda-alb we just created,

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‫and we click on create target group,

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‫which has now been created,

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‫so if I refresh this,

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‫I can choose demo-tg-lambda as my target.

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‫So this is good.

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‫Now we can go ahead and create our load balancer

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‫and view it.

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‫So while this is getting provisions,

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‫let's have a look at our Lambda function.

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‫So if you go into Lambda right now,

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‫we have a Lambda function with

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‫some very simple code,

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‫and that just returns the status 200

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‫and says hello from Lambda.

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‫So if we go ahead and test this function

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‫with a new test event and save this,

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‫test event, we just have to name it.

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‫Okay, and we go ahead and test this one.

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‫We can see, "Hello from Lambda" with a status code of 200.

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‫So this is good.

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‫Now let's add a little bit of logging.

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‫So here I will just have console dot log,

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‫and then event.

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‫This is to see what event is going to be passed here.

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‫So if I deploy first the changes,

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‫and then test my function as we can see,

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‫oh, and it's not console dot log of course,

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‫it is going to be print.

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‫So print, and then event.

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‫Let's deploy this function and test it,

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‫and now we get a hello from Lambda,

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‫and here we can see

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‫that the event that was passed is being printed

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‫to the console.

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‫And this will be helpful,

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‫when we want to see the event pass to another function

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‫from the load balancer.

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‫So back in the load balancer, let's refresh this,

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‫and here is the DNS name, and the status is active.

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‫So if I go and open a new tab and press enter,

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‫as you can see, this gave me a response of type DNS,

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‫so if I just go and open this file in a text editor,

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‫what I get out of it is hello from Lambda.

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‫So if we go back into our load balancer,

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‫this is because while we respond with hello from Lambda,

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‫but what we would like to have this response

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‫not to be downloaded,

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‫but instead to be displayed in my web browser.

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‫So to do so, let's do example Lambda load balancer AWS,

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‫and we have a documentation called

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‫using Lambda with the application balancer.

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‫And this is what the request looks like,

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‫we'll have a look at it in a second,

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‫but this is what the documents for the response should be.

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‫So we need to respond with something like this,

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‫and this is going to be interpreted correctly

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‫by my load balancer,

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‫and this will make sure we receive a proper HTTP response.

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‫So back in here, I'm going to, instead of returning this,

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‫I'm going to return the document I just found online.

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‫So we deploy these changes,

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‫and test our function

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‫by going directly in the load balancer,

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‫refreshing this page,

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‫and as you can see, I get the hello from Lambda,

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‫which was coming from my body text right here.

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‫So this first part is working,

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‫and if you want to do some examples,

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‫you can for example, change your text.

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‫The magic happens because in the headers we set

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‫the content type to be text html,

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‫and therefore this is deployed in our web browser,

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‫and we can change the status code here to be 200, and so on.

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‫So this is how a Lambda function is properly

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‫sent in data into our ALB,

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‫and then our ALB showing the data directly

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‫from the web browser itself.

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‫The other thing we can do

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‫is to go directly into the monitoring tab of our log

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‫for our Lambda function,

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‫and we can have a look at the recent request,

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‫so we can have a look at what is the type of event passed

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‫from the ALB into the Lambda function.

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‫So let me click on this one right here, this log stream.

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‫As we can see in this log stream,

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‫we have this query right here,

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‫this JSN document,

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‫which represents the type of information

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‫that the ALB will invoke our Lambda function with.

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‫This is the same thing that you will find

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‫in the documentation around here.

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‫This is the request event of the ALB to the Lambda function.

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‫And this is how you can, for example, look at the path,

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‫the HTTP method,

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‫the query string parameters, and so on,

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‫as well as the headers.

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‫So talking about the headers,

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‫as you can see here,

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‫I have a header where each header has a unique value,

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‫but if you go into your target group right here

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‫and you go to attributes,

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‫you can configure multi-value header,

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‫and if you allow multi-value header,

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‫this allows the load balancer

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‫to have multiple headers on here.

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‫So here, for example, you could have multiple values

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‫for the accept, or the host, or the user agent, and so on.

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‫So this is a feature you would just have to know

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‫for the load balancer,

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‫and you would need to modify the Lambda code

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‫a little bit as well for this to work,

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‫because right here the headers are sent just as key values,

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‫but if you enable multi-value header,

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‫you need to change your response a little bit.

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‫But I just wanted to show you this option,

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‫so you know it's a target group type of option.

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‫So let me, I should disable it right now.

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‫And that'll be it.

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‫And I also want to show you

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‫how this Lambda function was invoked.

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‫So as you can see, if you go under configuration,

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‫you see for the triggers

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‫that we have our application load balancer of course.

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‫But if we look at the permissions of our function,

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‫as you can see right here,

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‫we have a resource based policy statement,

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‫and this policy right here,

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‫if we click on the statement ID,

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‫allows my load balancer to invoke my Lambda function,

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‫which is great and what we want.

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‫So this is the condensed form, but you can do view policy,

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‫and do the actual entire JSN document to do so.

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‫So as we can see, this allows,

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‫thanks to the resource-based policy on our Lambda function,

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‫this allows our ALB to invoke our Lambda function.

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‫So that's it for this lecture.

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‫Now all you need to do to clean up

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‫is just to delete the load balancer,

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‫and you'll be good to go.

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‫Okay, that's it.

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‫I hope you liked it, and I will see you in the next lecture.