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Alone will come back still without permission.

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Now let's find out what is that story about intrinsic functions.

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Inculturation so interesting functions are nothing more than built in functions and there are several

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ones that will help you manage your stacks.

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Why do I need to use it.

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There are some variables or parameters that will not have values until your infrastructure or your stack

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is created.

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The runtime basically like what.

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Let's assume that I need the instance ID for that easy to instance created because I need to pass it

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on to another service or another application or two eventually to ACM in order to create a certificate

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that includes that piece or that instance ID.

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This will not happen until you launch the instance.

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So intrinsic functions will help you with that.

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So interesting functions use it in your templates when to assign values to properties that are not available

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until runtime.

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I need to know the availability zone where the instance is launched so I can use or I can enable then

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will be to be configured in a public subnet in that it is also the load balancer will be able to run

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to it.

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That is another example.

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So where in my template can I use the Internet functions.

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And it goes this is very important so I can use intrinsic functions in what sections of the template

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in the resource section in the output section in the meta data attributes or meter reader section.

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So there are three sections you can use them and also as we learn later on from the resource attributes

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in the update policy attributes resources they have attributes and we'll talk about that later on in

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their resource attributes are creating an update policy.

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Also you can use intrinsic functions where for locations or parts of your template resources in the

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output in the meta data and in update policy attributes.

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You can also use intrinsic functions to conditionally create stack resources.

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So what are some of importance.

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I mean there are plenty and we will go now to a website and I'll show you the full list but get you

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to find in my reference or ref get Easy's import value.

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These are ones that you may use frequently when you are dealing with cloud formation templates and if

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you follow this your L you will get to the interesting function reference the list of intrinsic functions

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and what do they do and all that.

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Let's now head to their website and I'll show you the full list.

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And we'll go through.

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What do they do exactly.

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OK.

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So if you say all I have and in fact you wrote cloud formation is a guide template reference intrinsic

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functions reference.

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So this is the list of functions that we can have.

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Base 64 cyder blocks find the map get up get easies and other functions so let's look at the ones that

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are of interest to us.

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So let's look at the find the map.

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What does it do.

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So the finding map function call column finding map returns the value corresponding to two keys in a

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two level map that is declared in the mapping section.

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OK.

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And there is adjacent template and there's the template.

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And here we have an example.

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So here is the mapping.

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It's called a region map.

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And then I have the region the type of virtualization that I'm going to use and how many bits.

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And then you find the a.m.-I and if it is VMG to then a different might.

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So basically this is a lookup table then it has the region as a variable.

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It has the type of virtualization as a variable and then you get the value for what you are looking

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for which is they might use and here under the resources section I'm going to have in finding maps here

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is the function that I'm using the name of that is region map and here's the normal counterpart to that

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right.

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So let's look at the next one.

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Get attributes.

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What can I do with that.

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Get attribute.

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So the function call and call and get attribute intrinsic function returns the value of an attribute

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from a resource in the template like what like if you want to get the instance ID if you want to get

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the DNS name.

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And here's the format.

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And if you scroll down you can find an example here.

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Function get attribute.

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Where does that get at.

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What's the name of that attribute.

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I'm looking for my email be.

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If you go to my Ill be here get daisies in the next one.

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So it is easy returns an array that list it is on for a specified region.

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So what you need to search the region and then it will get you a list or an array of what it isn't are

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available there and this will help you avoid too hard code.

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The list of everything zones for a specified region to get the parameter What is the list.

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What are the owns and act based on that.

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And here's an example function get everybody's own import value and then reference these will be the

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next to that we look at the function import value returns the value of an output exported by another

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stack like what if I have two groups developers and network an application or developer and the network

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are going to build the BBC they're going to put this up next day.

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I want now for the developers they want to launch an easy to instance but they need to get submit ideas

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or submit ID name that was created or the VBC details that was created by the network team.

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So now if the output of the stack configured or created by the network team includes these variables

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the BBC includes the subnet IDs and all that then these guys in the developers team they can reference

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that they can call that using the import value from the network stack output into the easy two instances

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or the developers or the application developers stack that template that they are creating.

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So if you want to do a cross-reference this is the craftier cross-reference between stacks then import

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value is a handy one that you can use.

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So here you have export in stack a.

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And these are the variables.

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And instead be I'm going to import as you can see here function import value and then the reference

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for what you're trying to get for the subnet ID from the other stack.

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If your important thing that you cannot delete a stack that you are referencing it's one of its outputs.

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You cannot do that.

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You cannot modify or remove an output value that is referenced by another stack.

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You cannot do that as well because you are importing it.

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And one important thing is that you cannot create the cross stack reference across regions.

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So things to keep in mind just in case if it pops up in one of the scenarios then you have that in mind.

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So we look at is reference let's see what difference does intrinsic function that returns the value

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of the specified parameter or resource.

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Now remember before when I said that when we have resources the resource can also be referenced from

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the output.

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And when we had the mapping the mapping could have been referenced from the resources then you need

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to use that F in order to point to something else to our parameter in a different section of the policy.

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And here we have an example then I'm referencing my easy to instance and that will be a part of the

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policy where you have my easy instance.

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So what will the reference return to you.

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It will return the instance ID from the section that included in the resources that included my instance

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my easy to instance.

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OK let's not talk about resource attributes so in the resources section each resource can have attributes

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different attributes so that of course you can.

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And we'll talk about them right now.

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They are used to further control additional resource relationships and behaviors of resources specified.

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And what are examples of that creation policy.

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Why would I need to do that.

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Why would I need to have a creation policy for that resource.

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Let's say you are creating.

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And you'll be on I'm not just kidding group and you don't want the auto Skilling group or that be to

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launch or to be created before the respective back end easy to instances will be created deletion policy

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if you want to retain or create snapshots or resources before they give you the template.

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Give me an example.

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I have an obvious one in half an hour the instance and I would like to keep the data in the database

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and I don't want that to be deleted.

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I can have a division policy attached to the resource that I've created for this instance.

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When the time comes to delete the stack snapshot it first before deleting or retain the audience instance

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don't delete it at all.

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That's the three buckets I wanted deleted it on retain it depends on so you can define dependencies

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between the source specifies the resource creation is dependent on the creation of another resource.

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If you want to add more meta data to your resources and update policy defines how the resource update

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should be carried out let's look at the creation policy to take the creation policy and I'll talk about

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the deletion policy in the next lecture because they are very important in the future.

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Frequently in the cloud for Mission questions in the exam so creation policy you can associate a creation

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policy attribute with a resource under the resources section in your template.

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Why to prevent its status from reaching create complete until something happened signals or some time

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has lapsed.

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When will the creation policy be invoked only when clutterer mission is going to create the associated

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resource.

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Because the creation policies are attached to the resource What are the resources that support creation

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policies now all or killing group instances and weight condition so use the creation policy attribute

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when you want to wait on the resource configuration actions before creation proceed so you have to hold

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everything until that happens and then you can persuade condition.

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Very important.

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So yes it is a cloud formation resource and the is weight condition.

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Use it with creation policy attribute.

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You can do the following.

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You can coordinate stack resource creation with other configuration actions that are external to the

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stack creation drag the status of a configuration process.

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Examples.

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You can start the creation of another resource after an application configuration is partially complete

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or you can send signals during an installation and configuration process to progress which would be

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important in finding out what happens especially if you're talking about test and development or in

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production such that if something happens you can go and look at the logs and the progress and find

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out what what happened and you can use it to instruct a mission to delay the creation of resources until

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an application has launched successfully on an easy to instance.

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Right.

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So that was the creation policy which is an resource attribute configured under a resource in your cloud

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formation resources section in your template.

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OK let's take a break and I'll come back and talk about an important attribute resources which is the

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deletion policy as well.

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But in the next lecture after the break I'll see you then.

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Thank you.