Read, Generate, Modify Configurations

8. Count and Count Index

Hey everyone and welcome back now In today's video we'll be discussing the count parameter and its associated configurations. So now the count parameter on resource can simplify the configurationsand let you scale resources by simply incrementing a number. This is the high level definition and we'll be discussing it more in detail in a moment. Let's go ahead and understand the need for the count parameter on resource. So, let's say you need to create two easy two instances. One common approach here is to define two separate resource blocks for AWS underscore instance, so you will see that you have one block for instance one and a second block for instance two. So, if you do a TerraForm plan, it will go ahead and show you the plan for two different resources that need to be created. So let's say you need ten easy to instance, so you'll have to copypaste this ten times, so that is a bit of a pain and even your code will become quite long, so what you can do instead is you can make use of the count parameter. With the count parameter, you can simply specify the count value and the resources can be scaled accordingly. So all you have to do here is you have to specify count is equal to five or maybe count is equal to twenty, so then what will happen is 20 easy to instance will be created. Let's try this out now from the configuration file. Let's go ahead and remove the other resources Let's go ahead and add a count parameter and let's say we'll say count parameter asthree. Let's go ahead and save this now. Let's clear the screen and let's do a TerraForm plan. Now, as expected, now you can see that there are three resources to add. Now you have the instance, you again have one more instance, and you have one more instance. Now do remember that here it starts with zero. So zero is the first, one is the second, and two is the third. So this is one important thing to remember. great. So I hope at a high level overview you understand the importance of the count parameter. The next important aspect here is the count index. An additional count object is now available in the resource block where count is set,an additional count object is available in expression.So you can modify the configuration of each instance. So this object has one attribute that we are discussing, and that is count index. So the distinct index number, which is starting from zero, corresponds to the instance over here. So, again, this might be a little confusing if you just look into the definition. Let's look into it with a practical usecase so that it becomes better understood. So let's understand the challenge by just using the count parameter. Now, in the below code, TerraFormwill create five IAM users. But the problem is that all will have the same name. So this is the Im user. The name is Load Balancer. If you do have an account, what will happen is that all of the users will have the same name as Load Balancer.And the application will fail for resources that cannot have the same name. So, by just using the count parameter, it does not really become the best of the approaches. Specifically, whenever you want some kind of loop or iteration. So let's look into it practically. So if you see that we have an iM user, whose name is Load Balancer, the count is five. So let's go ahead and see what happens when you do a TerraForm plan. So let's do a TerraForm plan here. So far, you can see that you have five different IM users that have been created. Again, you see, it starts with zero, so you have 01234. So in total, it is five different resources. Now, ideally, you want each resource to have a unique name because the same name may not always work or may not be expected in certain situations. So let's say that you are planning to create five new EC2 instances and all of the EC2 instances have the same name. So then it becomes difficult for you to identify the EC's two instances from the consultants. Everyone has the same name. So what you want is five different instances to have five different names so that the identification is simpler. So, in order to overcome this specific scenario,you can make use of the count index. So now what will happen is the count indexallows us to fetch the index of each iteration in the loop, so currently there are five counts and you have load balancer, count index. So now what will happen is it will go through each iteration and the count index will be changed accordingly, so it would be load balancer zero,load balancer one, load balancer two, and so on. So let's try this out. So within here, you can specify the count dot index over here. All right, let's go ahead and do a safe terraform plan yet again and now if you look into the name, you have load balancer four associated with the four. You have load balancer three, load balancer two, load balancer one, and load balancer zero. So this will effectively create five different imusers, each of which will have a different name altogether. So I hope at a high level overview, you've got the importance of the count index. So generally, whenever you do a count, what will happen is it acts as a loop, so this resource will run five times. Similarly, each time the resource is run in an aloop, this count or index will be incremented, so the first time it runs, it will have a value of zero so whenever this runs.For the first time, it will be load balancer 0. The second time it runs, it will be load balancer one and so on. So that is the importance of the count index. So now let's move one step further and understand the challenge. Whenever you are making use of a default countdot index, having a username like load balancer zero or load balancer one might not always be suitable. It becomes really difficult to understand what the purpose of loadbalancing zero, load balancer one, and so on. So better names like dev hypnot balancer, stagehyper load balancer, or fraud hyper load balancer are much better, and you can tell from the name that this dev hypoder balancer may be used for development, the balancer may be used for production, and so on. So you need a naming convention similar to this. However, you still need the counter index so that it can quickly iterate through it. So what you can do is you can make use of a variable, so let's say you have a variable of EIP underscore name where you specify a list, so you have a dev load balancer, a stage load balancer, and a fraud load balancer, and then what you can do is you can do a countdown index on this specific variable. So on the first iteration, the countdown index will have a value of debt load balancer, on the second iteration it will have a value of stage, on the third it will have a value of broad, and so on. So this is a really great aspect and this is something that is much better than just doing a planned iteration based on content, so let's look into it in a practical way as well. Let's go ahead and create a new variable, the variable name. Let's call it EEP names, and the type that we'll be specifying would be list. Let's specify a default value here. First we'll call it a "dev load balancer." The second would be the stage load balancer, and the third would be the prod load balancer. All right, so we have the variable that is defined. So now what we want is we do not want the count index to iterate through the number and use the number which was part of the count. We want to iterate through the values that we have as part of the variable of ELB underscore names. So now what you can do is first specify the ELB underscore names. This is something that we already know. So YELP underscore names will get the value from ELB underscore names. However, we can also make use of the count index. So let's try it out. So I'll say count the index over here. Let's do a save. Now, the only change that you have to make is to change the count. Since we only have three names over here,you can change the count to three. Let's do a series again. So from the CLI, let's do a TerraForm plan. So now if you look into the name, for the third one, you have a fraud load balancer. For the second one, you have state, and for the first one, you have the dev load balancer. So let's go ahead and also do a TerraForm application so that we are sure that everything is working as expected. Let's do a yes, great. So our resources are created and confirming it.From the CLI, you should see that there are three users called "DevST agent broad load balancer."

9. Conditional Expressions

And welcome back. Now, in today's video we'll be discussing the conditional expression. Now the condition expression uses the value of the boolean expression to select one of the two values. So if you look into the syntax of the aconditional expression, you have your condition and you have a true value and a false value. So if this condition matches, then this is the value that will be used. If it does not match, then the false value is something that will be used. So let's go ahead and understand the need for conditional expression with a simple example. So let's assume that there are two resourceblocks as part of a TerraForm configuration file. So this is the TerraForm configuration file and you have two resource blocks which create an EC2 instance. Now what you want is that, depending upon the variable value, one of the resource blocks will run. So let's say that there is a variable called Iftest. So what it basically means is this: in the environment that you are planning to create a TerraForm, is it going to be used for testing purposes or is it going to be used for production purposes? Now if it is going to be used for testing purposes, then what will happen is that the developed configuration will be executed? If the variable associated with the test is false,that basically means that the environment that needs to be created is not a testing environment. The resource associated with the production block will then be run by TerraForm. So this specific approach can be solved with the help of conditional expressions. So let's jump into practical sessions so that this can be better understood. So for today's demo, we have a file called "conditional TF." And in this file, there are two resource blocks that are available. One is for death and the second resource block is for fraud. This is very similar to having one resource block for the dead and another for fraud in the TerraForm configuration file. Now, when you do a TerraForm plan over here,what will happen is the TerraForm will create both the development as well as the broad related resources. So let me quickly show you this. So when you do a TerraForm plan, there will be two resources that will be created. So, if you go a little higher, you'll see the Prod instance. So the prod instance has a T of two large. So this is a bigger instance and you have one more instance which should be dep, which is T two micro. So I hope you understand this basic approach. Now what we want is that we want the developer to specify if they want a dev or a prod instance. If they want to create a demo instance,they should be able to do that. If they want to create a prod instance, they should be able to do that from the same configuration file. So in order to achieve that, what you have to do is create a variable. Let's create a variable called istext. all right? So this is the variable now, similar to the diagram. If the test is true, that means the environment the developer is trying to create is a test environment. Then, automatically, the def resourceblock will be executed. If the value associated with the istest variable isfalse, then the broadresource block will be executed. So what we have to do is to add a specific condition to each of these resource blocks. So let's try it out. So what we can do is we can add a count parameter and we'll say VAR is test is equal to true. So if the VAR is true, then the value associated with the count is one. Otherwise, the value associated with the count is zero. So this would make more sense if you had gone through our count video. So what will happen is if the value associated with tests is true, then the count will be one. That basically means that one EC2 instance will be created with the configuration that has been specified over here. If the value is false, then the count will have zero. That means no EC2 instances will be created from this specific block. Now, in a similar way, let's also define a count here. So I'll say VAR is test is equal to is equal to false. And if it is false, then we want the account value to be one. So one EC2 instance will be created from this broad resource block. And if it is true, then we do not want any EC2 instances to be created. So let's do one thing. Let's try it out. Before you can try it out, you have to assign a value associated with the specific variable. So I see that there is a typo here. Let's fix it. So now let's create a new file. I say TerraForm kfwat. This time we'll give a value of true. So now we know that if a value of true is given,then this specific resource block will have a count of one. So two micros will be created. So let's try it out. Let's do a TerraForm plan. And ideally, here you should see two micro-resources that are created. Now you can also change this number to three. So now what will happen is that if the value associated with the test variable is true,then the count will be three. So this in turn is something like when you explicitly define "count as three." So this is what it is exactly. So let's try it out. So I'll see the screen. Let's do a TerraForm plan yet again. So now you see that you have three resources and all of the resources are based on the two micro instance types. great. So depending upon the value here, this value basically fulfils this specific expression. Now let's give a value of false. So when you do a value of false, what will happen is that this specific expression does not hold true. And this is why the count of zero will be used. That basically means that this EC2 instance will not be created. However, on the other hand, since we have given the value associated with the STSS as false, then the first condition will be used,which is basically the true value. So let's try it out. So when you do a TerraForm plan this time, you should see an instance type of two large that would be created. So if you go a bit down, you see that this time you have two large base instance types that are being created. great. So whenever you are writing the conditional expression, just remember that the first part is the condition. So in this case, this is the first part. Then you have a question mark, and then you have the true value. So you see, you have a questionmark, you have a true value. So the true value is three in this case. And then you have a false value. The false value is zero. So I hope you understood the basic syntax of the conditional.

10. Local Values

Hey everyone, and welcome back. Now in today's video we'll be discussing the local values in TerraForm. Now a local value assigns a name to the expression, allowing it to be used multiple times within a module without repeating it. So there are multiple use cases for local values. Let's discuss one of the simplest ones where what we are doing is within the locals. We have a common underscore tag and are defining two key value pairs. One is that the owner is the DevOps team, and the service is the backend. So that's what we're defining among the locals. Now, within two A S resources, one is an AWS underscore instance and the second is an AWS underscore EBS underscorevolume, and both of them support tags. So we're doing local commonunderscore tags, or local common underscore tags, within the tags. So now what will happen is that any resource that gets created, this resource will inherit both these keyvalue pairs as part of the tags over here. Now if you're not using that, then one of the primary ways is that you have to add both the owner as well as the service within the tag of each of the resources that you create. So this is one of the simplest ways in which you can achieve that. So let's quickly look into it so that it can be better understood. So currently I have a file called LocalypeTF and I have defined the configurations here. Now if you see here within the first section, you have the local within here. You have common underscore tags where we have defined two key value pairs. One is the owner's DevOps team. The service has a backend. Within the three resources that we have over here, within the tags, we have specified local common underscore tags. So this EC2 instance that will be created will have these two tags. The same goes with the second EC instance. Again, the second will also have these two tags, and the same goes with the third EBS volume. The third EBS volume will also inherit the time. So you can define it only once and it can be used in multiple places. So let's go ahead and do a TerraFormPlan to understand how it might work. Now, if you go back up, you will see that there are a total of three resources that need to be added. first resource, you will see the tag as owner and service. So this is the EC's two instances here. The second EC2 instance has the same tag as the first, and the third EC2 instance has the same tag as well. So this is one of the ways in which you can use the local values for multiple resources. Now, apart from the static values, one of the great benefits of local values is that they support multiple use cases that can include conditional expressions, functions, and so on. So if you see over here, we have a name underscore prefix and now we have the conditional expression over here. So, if you need to refer to this condition expression in multiple resources, instead of hard coding the entire expression in each resource, you can put it in local and then say local name with underscore prefix from the resource. Now, in a similar way, if I have to show you from the documentation, under the locals they have the instance ID and you have basically the contact function and these are basically the arguments over here. So the entire function and the associated arguments are within the local. So from the resource, if you have to use this function and the arguments, let's say there are file resources where you have to use the same function and the associated arguments. So instead of copying and pasting this function into high resources, you put this entire function in inlocals and from the resource just refer to local instance underscore IDs and that's about it. all right? So I hope at a high level, you understand the importance of local values. So let's look into some of the important pointers for local values. The first one is that local values can be helpful to avoid repeating the same values or expression multiple times within the configuration. This is something that we have already seen. The second important point is that if local values are overused, they can make a configuration hard to read by a future maintainer by hiding the actual values that are being used. So you should use local values only in moderation, in situations where a single value result is used in multiple places and that value is likely to be changed in the future.

11. Terraform Functions

Hey everyone, and welcome back. Now in today's video we'll be discussing the TerraForm functions. So the TerraForm language includes a number of built-in functions that you can use to transform and combine values. The function name is now followed by a comma separated argument in parentheses in the general syntax for the function call. So if you see, you have a function. So this would basically be the function name followed by multiple arguments that are supported as part of the function. So, in the example above, you have a maximum of phi twelve and nine. So max is basically the name of the function. Phi twelve and nine are basically the arguments, and the output of the function is twelve, which is basically the maximum of all of these three numbers. So this is one sample function that is available in TerraForm. Now, the TerraForm language does not support user-defined functions, and so only the functions built into the language are available for use. So there are multiple categories that are available for functions. Like you have numeric, string collection, encoding, filesystem, you even have date and time, hash,crypto, IP network and type conversion. So these are the high-level categories, and within the categories there are multiple sub-functions that are available. So let's quickly look into a post which we will be discussing in more detail. Now, if you look into the TerraForm page of built-in functions over here, this is the page over here. On the left hand side, you have the high level categories here, so you have numeric, string collection, and so on. If you expand this, you have multiple functions. For example, within numeric, you have max, min, and so on. Within the string, you have format,lower join, and so on. So each high-level category has multiple functions that can be used. So one of the ways in which you can test this function is with the help of the TerraForm console command. So let's look into it. So currently I am in the CLI, so let's do a TerraForm console command and now you've got a prompt. So here you can go ahead and try various functions to see how exactly they work. So let's say you do a max on1020 of 30 and the output is 30. In a similar way, when you do a min on102030, the output you get is a ten. So the functions that you want to try out can be done within the TerraForm console command. If things are working as expected, then you can add it as part of your TerraForm configuration. Now, one of the good things within the documentation is that for each function they have given an example. So for an example of the max function, within the max function, you have various examples that are available. So let's open up a few more. So let's say split. So again, for split, you have the basic syntax and they have given you the example and they have also shown you the output of what exactly the split function will do for you. So this is really great for understanding what a function does at a high-level overview. So let's do one thing. Generally, when you do it in this way, it will not really give you a good amount of knowledge as far as practical experience is concerned. So what we'll do? I already have an already made TerraForm configuration file that I have created and that file has been using multiple functions. So we'll use that file to understand how functions are used in a real world environment. So for today's video, I have a file called "functions. TF" and this is a simple file. All it does is it creates an easy instance and it creates a key pair to login. So far, these are the only two resources that it has created. Now, within this, we have made use of multiple functions so that it allows us to understand how exactly it works. Apart from that, we have also defined functions at different locations. So, within locals, we have a date format function and a timestamp function. Then you have a map also available. Then you have a function of file, and you have a function of lookup as well. And if you go a bit lower,you also have a function of elements. So few functions are being used. Let's go ahead and try to understand this. Now we start with the resources of an AWS underscore instance. This is something that we have been using extensively within the course. So I hope you know what this resource does. Now, if you look over here, let's start with the first one where we are defining the AMI. So within the AMI, we are making use of a lookup function where you have the VAR a Mi and VAR region. So first let's look into the VAR region over here. So if you look into the variable of region, the default region here is the AP South one, which is Mumbai. And this lookup is also making use of one more variable, which is War AMI. So why dot? AMI is nothing but a map. So what this map does is it basically links a region to the associated AMI ID. So US east one has a unique AMI IDE, US west two has a unique AMI ID, and AP South one has a unique AMI ID. So I hope you understand what VARa Mi is and what the VAR region is. Now, the question that comes is What exactly is the lookup function? So, coming back to the documentation, let's go to collections and you should see a lookup function that is available. So let's look into it at a high level. So what look-up does it basically retrieve the value of a single element from a map given its key? So this can be better understood with the syntax. So you have a look up, you provide a map, you provide a key, and you also have a default value that will be written if it does not match the one on the map. So, within the example, it can be better understood. So basically, you have a map like A is equal to A, b is equal to Bee. Then you provide the key. So the key is A and the default value is what? So what will happen is that the lookup function will return the value associated with A. So in this case, the value associated with A is Ay and that is the reason why you are able to see A within the output. Now, in the second example, you are trying to look up the key of C, which is not present at all within this given map. So now what will happen is you also have a default value. So if you see, this is the default value. So if things are not part of the map, then you will get the default value in the output. So this is what the lookup does. So let's try it out once. So I'll copy this up. Now, within the console, if you run this command, you should get the expected output, which is a y. If you replace the key with B, you should see the output bee over here. And in a similar way, if you replace the key with a certain nonexistent key like Z, then it will give you the default one, which is what? Now, if you look into a lookup function Here, the first part is the y a mi. So y a mi is nothing but this map that is being provided. So if you see this is nothing but the map over here, then you have the VAR region and the VAR region. As we have seen, it is the AP South one. So now what it will do is look into the AP South one inside this map and then it will return you the associated Amiid over here. So that is exactly what this lookup does. So the final result of this AMI would be the AMI ID that is being associated with the AP South region. great. So that is what the AMI lookup function does. So I hope you are starting to get the gist of how beneficial functions can be. great. So that is the first lookup function that we are using. Now the second thing is to count. We have already seen what counting does. So basically, this will create two easy instances. Now within tags, you are making use of the element function over here and you are making use of VAR tags followed by the count index. Now, the count index is something that we have already seen earlier. So let's look into what VAR tags do. So if you go a bit higher, you have a variable of tags. The list and default are types. There are two tags that are available. One is the first EC two, and the other one is the second EC two. So these are the two tags that are available. So you have the first EC two, second EC two, followed by the count index. And then you have the element function. So in order to understand this properly, we need to look into what exactly the element function is. So in the documentation, let's go to the element function. So if you see an element, retrieve a single element from a list. So the syntax is element, then you provide an alist, and then you provide the index over here. So within the element you see in the list, there are three items; you have A, B, and C. And then you provide the index. So indexed here is one. That's why you are seeing B. So let's try it out. So I'll copy this up and let's paste it. So here, the element that will be returned is B. Now remember that everything starts with a zero. So this is the zero, this is the one, and this is the two. So when you press Enter, you get B. When you do zero, you get an A, and when you do two, you get a C. So all the element does is, depending upon the index that you provide, which is zero, one, or two, it will retrieve one of the items that are part of the list. So now you can better understand it. For the first time, since we have a count of one, what will happen is that the counted index will be zero. So the second time, the count of the index will be one. When the count of the index is zero, the element that is returned is the first EC two. The index count will be one the second time, and the second EC two tag will be returned. So now what will happen is that the name of the EC Two instance here will be changed. The first name will be changed to EC Two. The second EC Two instance that will be launched will be named EC Two. So that is what the element does. Now we'll be doing this practically in terms of TerraForm application, so that it becomes better understood. But first, just understand this at a high level, which we'll be discussing in detail now. In fact, let me do one thing. Let's do a TerraForm plan so that this becomes better understood. So from the CLI, let's do a TerraForm plan. So within the TerraForm plan, what will happen is that the value associated with the functions will be able to see that.So we know that this will go ahead and create two EC instances. So let's start from the top. So this is the first EC2 instance that has been created. As expected, you see the AMI, which is four, seven, and six, which we got from the lookup table, is associated with the AP South one. Primarily because within the lookup we had specified the WAdot region, which had the value of AP south one.Now, if you change the value of AP by one, then this specific AMI would be returned. So that is the first part. The second part is this element over here. Let's look into the tags. So if you look into the tag, the first EC two instance has a tag of the first EC two. Let's go a bit down. The second EC two instance has a tag of second EC two over here. All right, so I hope you understand what element function does and what the role of the count index is. If you are a little confused with count index, just go through our count videos where we discuss it in more detail. The next function that we make use of is the file function over here. So let's minimise this. And within the file system, you will see that there is a function called file and the syntax is file followed by the path. All it does is that it reads the content of the file at a given path and returns it as a string. So if you see you have a file,then you have a path module, which is basically the specific path followed by hello TXT. So what will it do? It will return the contents that are part of hello TXT in a string over here. So that is what it does. So let's try it out. So within here, what I have done is create a file. Everything remains the same. The only change is the IDRSA pub. So that basically means that the ECU instance that gets created will be created using this specific keypad. So let's clear the screen. Let's do a TerraForm console. And now when you press Enter, you see that you get the contents that are part of the ID underscore RSA pub file. Now, this file is within the same directory where our function TF is present. So if you look into this directory of functions,we have both the functions PF and idersa, and all the file functions have done. It has basically extracted the content of this file and presented it to you as a string. great. So I hope you understand what the file function does. Now, if you go a bit lower, you also have the output of a timestamp, and it is basically referencing the local time. Now, if you go a bit up within local, we actually have two functions that are being used. One is the format date, and the second is the timestamp. So these are the two functions that are being used. Now, if you go back to the documentation,if you see the timestamp, what timestamp does it basically show you the current timestamp? However, the current timestamp is not easy to understand over here. So what we make use of to betterformat it is the format date function. So within the format date function, do we have a spec? So there are multiple specs that are available. So you have Ddmy and so on. So, DDMM YY is something that is quite easy to understand. So we use this specific format here. So if you see we use the DDMby over here, then you have a comma. You see, you have a comma and the same over here. And then you have to specify the timestamp. So the timestamp is something that we retrieve from the timestamp function. So if you go to the timestamp here, this is the timestamp. And on top of this, we make use of formatso that we see this in better detail. So that's what the format and timestamp function does.great. So this is the high level overview of this specific TerraForm TFI. Now, if you see within the output what we are doing within the value, we have a local dot time, which is nothing but the local dot time. As a result, any value returned by this function will be outputted after the TerraForm is applied. So that's the overview. Let's go ahead and run this. So let's do a TerraForm application and let's put a yes. Now, if you see within the EC to keeper,you are seeing the exact keeper, which is basically the output of the file function that it computed. So let's do a yes. great. So in total, three resources have been created. Now if you look into the output, you have the output of a timestamp and it states the date as April 24, 2020, 1410 UTC. So this is why we are actually making use of format date, otherwise the output timestamp is a little difficult to read. From the ECT console, you will see that there are two EC, two instances that have been created. The first has the name of first EC Two. The second has the name of second EC Two. Essentially, what is happening is that you have a tag which has a name of first EC two and a secondtag which has a name of second EC two. great. So I hope it's a high-level overview. You understand what the TerraForm functions are. We look into it both by manually running the TerraForm console and also doing it practically to see how helpful TerraForm functions are whenever you are writing the TerraForm code. Now to remember that there are a lot of functions that are available. Now, it is not really feasible to cover each one of these functions in detail. However, once you understand the concept of functions and how we can use them within the TerraForm configuration file, then it is much easier to go ahead and understand the other ones that might be useful within the TerraForm code. Now, one thing that I will really encourage you to do is to practise this thoroughly and understand this video thoroughly,so you should be able to understand each of the functions that have been used and the exact.

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