In-place deployments are a deployment strategy in AWS where application updates are applied directly to existing instances without creating new infrastructure. This approach is commonly used with AWS CodeDeploy and is particularly relevant for the AWS Certified SysOps Administrator - Associate exam…In-place deployments are a deployment strategy in AWS where application updates are applied directly to existing instances without creating new infrastructure. This approach is commonly used with AWS CodeDeploy and is particularly relevant for the AWS Certified SysOps Administrator - Associate exam.
With in-place deployments, the application on each instance in the deployment group is stopped, the latest application revision is installed, and the new version of the application is started and validated. This process occurs sequentially or in batches across your fleet of instances.
Key characteristics of in-place deployments include:
1. **Cost Efficiency**: Since you reuse existing instances rather than provisioning new ones, there are no additional infrastructure costs during deployment.
2. **Deployment Configurations**: AWS CodeDeploy offers several configurations such as OneAtATime, HalfAtATime, and AllAtOnce. These control how many instances are updated simultaneously, balancing deployment speed against availability.
3. **Downtime Considerations**: During the update process, each instance becomes temporarily unavailable. Using load balancers helps manage traffic by deregistering instances during updates and re-registering them afterward.
4. **Rollback Capability**: If deployment fails, CodeDeploy can automatically roll back to the previous version by redeploying the last known good revision.
5. **Application Stop**: The existing application must be stopped before the new version is installed, which means brief service interruptions on individual instances.
6. **Lifecycle Hooks**: CodeDeploy provides hooks like ApplicationStop, BeforeInstall, AfterInstall, and ApplicationStart that allow you to run custom scripts during deployment phases.
In-place deployments work well for applications that can tolerate brief interruptions and environments where maintaining minimal infrastructure is prioritized. However, for zero-downtime requirements, blue/green deployments might be more appropriate. Understanding when to use in-place versus blue/green deployments is essential knowledge for the SysOps Administrator certification exam.
In-place Deployments: Complete Guide for AWS SysOps Administrator Associate Exam
What are In-place Deployments?
In-place deployments, also known as rolling deployments, are a deployment strategy where the application on each instance in the deployment group is stopped, the latest application revision is installed, and the new version of the application is started and validated. This process updates existing instances rather than creating new ones.
Why are In-place Deployments Important?
Understanding in-place deployments is crucial for several reasons:
• Cost Efficiency: No need to provision additional infrastructure during deployment • Resource Management: Maintains the same number of instances throughout the deployment process • Simplicity: Straightforward approach for updating applications on existing infrastructure • Common Use Case: Widely used in traditional deployment scenarios and frequently tested on AWS exams
How In-place Deployments Work
Step 1: AWS CodeDeploy identifies the instances in the deployment group Step 2: The application on each instance is stopped according to the AppSpec file hooks Step 3: The new application revision is downloaded and installed Step 4: The application is restarted on each instance Step 5: Validation scripts run to confirm successful deployment
Key Characteristics: • Instances are temporarily taken out of service during deployment • Can be configured to deploy to all instances at once or in batches • Supports deployment configurations like OneAtATime, HalfAtATime, or AllAtOnce • Works with EC2 instances and on-premises servers • Does NOT work with AWS Lambda or Amazon ECS
Deployment Configurations for In-place Deployments:
• CodeDeployDefault.OneAtATime: Deploys to one instance at a time (safest, slowest) • CodeDeployDefault.HalfAtATime: Deploys to half the instances at once • CodeDeployDefault.AllAtOnce: Deploys to all instances simultaneously (fastest, riskiest)
Advantages of In-place Deployments: • Lower cost since no additional instances are needed • Simpler infrastructure management • Faster deployment when using AllAtOnce configuration • Works well for development and test environments
Disadvantages of In-place Deployments: • Application experiences downtime during deployment • Rollback requires redeployment of previous version • Reduced capacity during deployment process • Higher risk compared to blue/green deployments
Exam Tips: Answering Questions on In-place Deployments
Tip 1: Remember that in-place deployments are only supported for EC2 instances and on-premises servers. If a question mentions Lambda or ECS, in-place deployment is not the correct answer.
Tip 2: When questions mention minimizing costs during deployment, in-place deployments are typically the answer since they do not require additional infrastructure.
Tip 3: For questions about zero downtime requirements, in-place deployments are usually NOT the correct choice. Blue/green deployments are better suited for this.
Tip 4: Understand the deployment configurations. If a question asks about the safest deployment method, OneAtATime is the answer. For fastest deployment, AllAtOnce is correct.
Tip 5: Know that rollback in in-place deployments requires redeploying the previous revision, which takes time. This is a key differentiator from blue/green deployments.
Tip 6: Questions mentioning reduced capacity during deployment are hinting at in-place deployments, as instances are taken out of service during the update process.
Tip 7: Remember the AppSpec file controls the deployment lifecycle. Questions about hooks like ApplicationStop, BeforeInstall, AfterInstall, and ApplicationStart relate to in-place deployments.
Tip 8: If a scenario mentions existing infrastructure that cannot be replaced or instances with specific configurations that must be preserved, in-place deployment is likely the correct approach.