Monthly Archives: June 2021

Preparing for Hashicorp Certified Terraform Associate Exam

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A quick article that helps you preparing for Hashicorp Certified Terraform Associate Exam

Terraform Associate exam!

In this quick post, I would like to share some of the resources that help you clear the terraform associate exam. Feel free to add resources you know in the comments section, which may help fellow readers.

The terraform associate exam is designed to test the candidate’s readiness towards IaC, i.e. Infrastructure as code. IaC concepts, terraform CLI hands-on (a lot of it) and knowledge on terraform’s paid offerings through Cloud or Enterprise should get you through this exam. It’s a practitioner level exam, so it shouldn’t be hard to beat if you have IaC and cloud background.

You must have researched already about the exam on its official page, but here are quick facts for your reference.

Topics to study

I suggest you have good hands-on with terraform CLI before taking this exam. It will help you cover the majority of topics, and you don’t have to learn them during preparation. That leaves you with minimal topics to prepare for actual certification.

Hashicorp’s study guide is the best resource to follow along for preparation. Let me quickly list down a couple of topics you should not miss during preparation –

  • IaC concepts
    • Traditional infra provisioning v/s IaC
  • Terraform basic workflow
    • Write, plan and apply.
  • Different types of blocks in terraform code
  • Terraform CLI commands (a huge list of them!)
  • Terraform Modules, functions, state files
    • At least go through all functions once.
    • Lots of hands-on to understand how modules works
    • State management (a big topic!)
  • Debugging and variables
    • Different ways to handle variables
    • Debugging levels, ways to set them, logging in files
  • Detailed understanding of Terraform cloud and enterprise
    • Free and paid offerings in each type
    • Sentinal, workspaces, remote runs etc. understanding
    • Clustering, OS availability in each type

Resources for preparation

Assorted list of online resources you can leverage to follow along your preparation journey.

I am linking here my own last day revision notes as well that I prepared during my certification preparation.

Practice tests

Here is a list of practice tests you can take online before going in for an actual exam. It will test the understanding of your topic and concretes your decision for exam booking.

That’s all I have to share. All the best!

How to create atomic counter in AWS DynamoDB with AWS CLI

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A step by step procedure to create and update atomic counter in AWS DynamoDB table.

Creating counter in DDB!

First of all, we will see what is atomic counter and why do we need it. We will also check why DybamoDB is chosen in this use case.

What is atomic counter?

Often it would help if you tracked some numerical like website visits, which are incremental in nature. Such counters need to be stored in a centralized place, and the update should be atomic. Atomic means one request executes without interfering with another request. i.e. concurrent updates do not clash with each other and so no data lost in the process. Since everyone is leveraging temporary infrastructure like EC2 getting replaced by Auto Scaling groups or containers, storing such counter locally is not a good idea. So to get central storage, DDB is the best choice since it’s an ultra-fast, single-digit milliseconds latency, NoSQL database. Perfect for the atomic operation of scaling infra/traffic.

Now let’s get into the process of creating this counter and updating it.

Creating DynamoDB table for the counter

  1. Login to DDB console
  2. Click on Create table
  3. Enter Table Name
  4. Enter Primary Key (Partition Key)
  5. We don’t need a sort key here since our table will carry only one counter value. Keep the rest of the settings default and click Create
Create DynamoDB table

You can use below Cloudformation resource block to create a DDB table:

Type: AWS::DynamoDB::Table
    Properties:
      TableName: kerneltalks-counter
      AttributeDefinitions: 
        - AttributeName: ID
          AttributeType: S
      KeySchema: 
        - AttributeName: ID
          KeyType: HASH

Make sure you change the TableName to your choice. You can also explorer other properties supported by DDB in CloudFormation.

Preparing DynamoDB table for counter updates

Now, you will be presented with newly created table details.

Goto Items tab and click Create item

Create DynamoDB Item

Add attributes in item as mentioned below :

Click on Save. Now your DDB table is ready for updating the counter

DDB table creation can be done via AWS CLI as well using the below command:

$ aws dynamodb put-item --table-name kerneltalks-counter --item '{"ID": { "S": "Counter" }, "TotalCount": { "N": "0" }}'

Updating counter in DDB table

Now you can use below AWS CLI command below to update the counter! Every time you run the command, it will update the counter by 1. You can code it in your application at the appropriate place to run this command/API call to update the counter.

$ aws dynamodb update-item --table-name kerneltalks-counter --key '{"ID": { "S": "Counter" }}' --update-expression "SET TotalCount = TotalCount + :incr" --expression-attribute-values '{":incr":{"N":"1"}}' --return-values UPDATED_NEW
{
    "Attributes": {
        "TotalCount": {
            "N": "1"
        }
    }
}

The command should return with the updated attribute in JSON format. You can format it to text for easy usability in code.

$ aws dynamodb update-item --table-name kerneltalks-counter --key '{"ID": { "S": "Counter" }}' --update-expression "SET TotalCount = TotalCount + :incr" --expression-attribute-values '{":incr":{"N":"1"}}' --return-values UPDATED_NEW --output text
TOTALCOUNT      2

The same can be verified in the console.

Counter in DDB.

That’s all! Now you have a counter in DDB which can be updated from different sources using API calls.