Prevent the auto-termination of stranded instances in RighScale

When you launch an instance with RightScale Self Service, and the Chef cookbook execution fails, the instance goes into “stranded” mode. By default RightScale Self Service terminates the stranded instances, so there is no way to remote into them and read log files to find the cause of the problem.

To keep stranded instances running in RightScale

  1. Find the booting instance in Cloud Management and click the instance name,
  2. Click the lock icon on the top of the screen

RightScale Self Service cannot terminate locked instances. To terminate the instance after the troubleshooting process, unlock the instance and terminate the instance by hand.

Upgrade a server on an AWS EC2 instance with minimum risk and downtime

When you need to upgrade an application on an AWS EC2 instance with minimum downtime, there are many options.

Upgrade an EC2 instance

  1. Stop the application, so users don’t make more changes,
  2. Create a backup of the database (snapshot of the RDS instance),
  3. Create a backup of the server (backup image of the EC2 instance),
  4. Upgrade the application on the server,
  5. Start the application,
  6. Test the new version of the application.

In case the upgrade fails, or the post-upgrade test fails

  1. Stop the application,
  2. If you use RightScale to launch servers:
    1. stop the RightLink service on the failed server to prevent RightScale auto terminating the restored server
      (When RightScale finds a new identical server instance, it automatically shuts it down to avoid multiple instances with the same identifier.)
    2. Terminate the failed server
  3. Stop the failed server,
  4. Restore the database from the pre-upgrade backup with a new name,
  5. Restore the server instance from the pre-upgrade backup,
  6. Start the restored server,
  7. Change the database address in the application’s config file to point to the restored database,
  8. Start the application,
  9. Test the restored version of the application.

To make the backup image of the AWS EC2 instance

  1. Open the AWS console and navigate to EC2, Running instances
  2. Find the server instance you want to backup
  3. Right-click the row of the instance and select Image, Create Image

  4. Name the image and click the Create Image button
  5. Save the image Id from the popup

Test your RightScale script without creating unnecessary revisions

There are certain functions in RightScale scripts (RightScripts) that you cannot test without launching a new instance. To test your script:

  1. Edit the Head revision of the RightScale script and save it,
  2. Attach the Head revision of the RightScale script to the Head revision of the RightScale Server Template,
  3. In your Self Service CAT file reference revision 0 (zero) of the Server Template (Head revision),
    ( “server_template_revision”  => “0”, )
  4. Upload the Self Service CAT file to Self Service, but do not publish it,
  5. Launch a server instance from Self Service using the RightScale Self-Service Designer page, not the Catalog.

If the script has some errors, modify the Head revision of the RightScale script and launch a new server instance using the RightScale Self-Service Designer page.

When the script works perfectly:

  1. Commit the RightScale script, creating a new RightScale script revision,
  2. Attach the committed revision of the RightScale script to the Server Template’s Head revision,
  3. Commit the Server Template, creating a new Server Template revision,
  4. Publish the new revision of the Server Template,
  5. Reference the new revision of the Server Template in your Self Service CAT file.

Find the AWS AMI that a RightScale server template is using

When you use RightScale to launch servers in the cloud, you want to use the same base image to test your Chef cookbooks in Test Kitchen.

Packer by Hashicorp is a utility to create custom server images based on cloud images. You supply the image ID and other configuration parameters to create a new custom image.

To find the AMI ID of the base image of the RightScale Server Template

  1. Open the RightScale user interface in your browser,
  2. Select the RightScale account where the server template was created,
  3. In RightScale Cloud Management select  Design / ServerTemplates,
  4. Select the server template,
  5. Select Images,
  6. Select the MultiCloud image,
  7. Select Clouds,
  8. Select the image in the region you are working in,
  9. The Resource UID is the AMI ID of the image.

DevOps Engineering part 7. – Launching production instances in the cloud

In the previous parts of this tutorial we have launched instances (servers) in the cloud, but those were created by Test Kitchen, running on our workstation. Those instances are as good as they can be, but the cookbook did not reside on the Chef server.

To launch pre-production and production instances in the cloud, first we need to upload the cookbook to the Chef server. In Beginner’s Guide to DevOps Engineering part 4. Connect to the Chef server we have already connected our workstation to the Chef server.

Upload the cookbook to the Chef server

To make your cookbook available for all the servers of the organization we will upload the cookbook to the Chef server.

  • In the folder of the cookbook open a Bash window
  • Execute the command to upload the cookbook to the Chef server
    knife cookbook upload COOKBOOK_NAME --freeze

    Don’t forget to add the –freeze option to the end to protect the version of the cookbook from accidental changes.

Launch the server in the Cloud

There are many ways to launch servers in a scripted way, we are going to review a few options. One is to use RightScale, a Cloud Management Platform, that can manage servers in multiple cloud environments.

RightScale

Create a new Deployment

  • Using your web browser log into the RightScale Cloud Management user interface,
  • In the Manage menu select Deployment and click the New button,
  • Enter the name of the new deployment,
  • To add the new deployment to your bookmarks,
    • On the left side in the Bookmarks section click the Add link,
    • If necessary shorten the name of the bookmark and click OK,
    • To reorder the bookmarks
      • Click the Edit link and drag the bookmark to the desired position,
      • Click the Done link to save your changes.

Create the CAT file

CAT files are Ruby like scripts that describe the configuration of the instance. It contain the name of the deployment the server should be placed it, the cloud attributes to assign security groups, regions, availability zones, set the drive size, specify security keys. The easiest way to configure a server is to copy an existing RightScale Self Service CAT file and update it with the new values.

If this is the first CAT file in your organization, get help from RightScale support and get a sample file from them.

If your organization already has a library of CAT files

  • Make a copy of an existing CAT file
  • Update the values to customize it for your server
    • Application name
    • Chef runlist
    • Security group
    • Deployment name
    • Load balancer name
    • Instance type

 

Upload the CAT file to RightScale

  • Open the RightScale Self Service user interface,
  • Select Designer on the left,
  • Click the Upload CAT button and select the CAT file,
  • Click the Upload button in the lower right corner,
  • In the green popup in the upper right corner click the Publish to catalog link,
  • In the lower right corner click the Yes, Publish button.

Launch the server in RightScale Self Service

  • In the RightScale Self Service interface select Catalog on the left side,
  • Select the catalog item you want to launch,
  • Enter a name for the instance to be able to identify it later and select the instance in the dropdown list,
  • Click the Launch CloudApp button.

To monitor the server launch

  • In your web browser open the RightScale user interface,
  • In the design menu select Deployments,
  • Select the deployment of the instance,
  • Click the instance to see in formation on it.

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