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Inspecting the Terraform State

Lesson Content

Getting Started with Terraform on SAP BTP

SAP_MOOC_terra1_unit3_lesson3_INSPECT_Video.mp4

Hello and welcome to Lesson 3. Looking at our journey, we are at the last step of our preparational setup. And in this lesson, we will be inspecting the Terraform state. That's also one of our learning objectives in this lesson. Understand what a Terraform state is at all. You will also learn how you can interact with the states to get information, also to know what certain things mean. And you also get an outlook on how you can actually store the state. But maybe before going into the hands-on exercise Christian, I think it's important to understand what a state in terraform is. Can you shed some light on this? Absolutely. So the state in terraform is one of the central ingredients of our setup. The main point to understand is that terraform keeps track of the state of the infrastructure that you provision and that you consequently manage via this state file. So the state file is an essential part of your configuration. Now the question is what does Terraform do with this state file, Rui? Well, actually it uses the state to map the configuration that you have defined in your script and maps it to the real resources on the respective provider. In our case, the SAP Business Technology Platform. And then it tracks the metadata like dependencies. For example, you can only create an entitlement for a subaccount if that subaccount is available, right? So, and much data, metadata dependencies, you will find in the state file as well. But where to find that state file, Christian? Well, in our setup, the state is stored locally within your file system. So you find it where you have stored your Terraform configuration. The file is called terraform.tfstate. We will see that in a second. This state file has a specific layout. Do you want to say a few words about, Rui? Yeah. So the state file is provided in JSON format and is human readable. So you can actually read through it and you understand how the various resources are related to each other. It's very easy to grasp, but one important thing that we need to make you aware of is that this state file also contains a lot of sensitive information like IDs or passwords in plain text. So very importantly, whenever you work with Terraform and you want to put these scripts into GitHub, please, the first thing you need to do is to add the state file always to the gitignore file so you don't upload it unintentionally. With that, you prevent to commit and push sensitive information to your Git commit history. So, but how to interact with the state? Are there some rules, some best practices, Christian, that we can share? Yes, indeed, there are. So, as we said, the state file is in plain JSON format, which means that it's quite tempting to directly interact with it, and that's a no-go. Never directly added the state file, because this is something that will likely cause issues in your terraform flow and might even corrupt the state file completely, and this means your setup. But how can we interact with the state then? Well, the Terraform CLI offers several commands to interact with the state. We will focus on reading the information that is stored in the state file, but do not manipulate the state while the Terraform CLI. While that is possible, that is a quite advanced topic. Rui, would you like to tell us what commands we can use for inspecting the state file? Yeah, sure. we have on the one hand side the command terraform show that provides a state file in the jason format that I was just talking about before then you can use the command terraform state list which provides you with the list of all the resources that are available within the state file so quite a good way to understand if all the resources are there that you actually wanted to have and another command is terraform stage show where you can also then see the details of a resource in the state file like the respective IDs or other meta information that is bound to the respective resource. But I think we have provided you now with enough theoretical information. I propose Christian, we go now hands on. What do you think? Yeah, let's go. We provisioned one resource up to now, so let's see what the state file looks like in our current terraform setup and walk through the commands that we just pointed out. Okay, so as usual, as you already know, we have all the description of what to do within our GitHub repository, so all the commands that you will now see are clearly laid out there with some of this information in Unit 2, Lesson 3, exactly. So let's directly jump into it and we have provided the subaccounts. So as you can see here, we have already a file called Terraform.tfstate, and that's something that we know, right? That's a state. I will open it now, but just for the sake of showing it. This is the JSON format. You see a lot of, let's say, metadata, and then you see the resources and a lot of information. Partly stuff that we configured, partly stuff that Terraform needs in order to manage things. now as we said before never ever added this file directly because we also see it not even editing but also sharing it unencrypted because you see there were some ideas in there which of course and at the end of this course will all be gone but nothing that you want to put somewhere unencrypted absolutely so think about if your provision databases there will be database passwords in there maybe and this is not nothing that you want to share with the wide world on GitHub. Now let's go to the commands. So first command that we have seen or that we have presented throughout the lesson, there is the Terraform show command. Now this just prints out the information of the TF state file in a human readable way. It gets rid of all the metadata information. It just shows us the one resource that we created. And, well, it's not super impressive because it's just one resource, but I think you can see now what is all in there. We also see those fields filled with that have been marked as known after apply during the planning phase. So that doesn't look too Chevy, right? We see here, for example, the sub-account ID, right? Over here, we also see the parent ID of that sub-account, meaning what is the idea of the parent? because you can also create maybe directories and then you would actually point the parent ID to that directory and yeah or as you said everything which is normally also shown in the Terraform plan as shown after apply or available after apply is now visible here. Okay then let's go to the next one and that's Terraform, that's a direct command that points to the state is Terraform state list that sounds super impressive that just lists all the resources that are available within your state and as we have just one resource well it shows one resource so we have the resource name BTP subaccount and then as you mentioned before the address of that resource project sub account listed and of course if you have more they will be showing up there as well exactly so if you compare it we have the resource we have the resource type BTP subaccount and then we have our address our name And that's exactly reflected here. And that's also how we can then get more detailed information. So if we do Terraform State show, and I'm too lazy to type, I will just copy this over. You will see now, again, the same information that we saw before with the Terraform show. Now, think about having provisioned several resources. Terraform show will basically explode because all the resources are shown in, one run. Now here you can directly target dedicated resources and look at the details of this one resource that you have. And let's shortly cross-check if we forgot something but I don't think so. So we have the Terraform stage show and... Yeah, so everything that we just talked about is also shown here in the Read Me MD file and I think that's it. That's it for this lesson, exactly. Okay, now as we have seen that we can look into the state file and the information stored in it, there is one thing that we want to mention and that's back ends. If you remember at the beginning of this course, we said that there is a team of administrators who wants to collaborate on providing infrastructure. Now, having the state file stored locally means that only the person who has the state file can also provision and manage the infrastructure. That's not our goal, right? So, we want to have collaborative work on the infrastructure and consequently the state must be stored centrally. Terraform supports that. The concept that Terraform provides us for that is the so-called back -end which you can configure to achieve a central storage of the state. These states then are no longer local states, but as they are stored remotely, they are called remote states. Terraform supports different backends out-of-the-box. Examples are AWS S3 bucket, an Azure blob storage, or HashiCorp Cloud Platform. Important to note is that these backend support state locking. That's something that's of course important, because if several people work on one state file or on one configuration, you don't want to have conflicting access to the state. If you want to use a remote backend and you must explicitly, Then you must explicitly configure it, of course, and this is something that goes beyond the scope of this course. You find all the details in the Terraform documentation, so if you want to have a professional setup, then, after you have walked through this course, I highly recommend looking into that specific documentation. With that, we are done for this lesson. What did we learn, Rui? Yeah, a couple of key takeaways, I guess. We learned that the state is really a very central element of Terraform. So to understand how Terraform has achieved the target state that you have defined, it contains the mapping between the configuration and the infrastructure resources and additional metadata that is provided along by the respective services that you have set up. We also learned that a state contains sensitive information and that we should give it some extra attention. Whenever you store it, it should always be encrypted or only available in a state. an encrypted way. We learned as well that you should not directly edit a state file because this can create all kinds of issues that will no longer make the Terraform script work. And as you also learned, the various commands that the Terraform CLI offers you are there to interact with the state. And with that, we have finished this lesson and unit. Looking forward to the next unit and the next lesson with you. Bye-bye.