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Chef Developer Workflows

Table of Contents

Objective

Show a recommended developer workflow for developing ServerTemplates using Chef cookbooks and recipes.

Overview

There are two basic types of workflows for Chef development.

  • Workflow using refetch
  • Workflow using rsync

The rsync program is available on Linux machines and can be used to synchronize file trees across local disks, directories, or a local network. In this example, rsync will be used to synchronize the cookbook repositories on your local development box with the cookbook repositories on the running server instance.

Which workflow is recommended?

Although you can use both workflows for Chef development purposes, some developers may find it more useful to use the rsync model. One of the key benefits of using the rsync workflow is that you can develop your code faster and more efficiently because you do not have to constantly push all of the changes to your repository and refresh them in the Dashboard before you can run and test the script on the server. By using the rsync model, you can author code on your local development machine and test the script immediately on the running server without having to perform the push and refetch steps every time. This way, you will only have to push the code changes after you have already tested them on a running server.

Note: If you are using the rsync model, you will never be able to refetch changes from your cookbook repositories. As a best practice, once you are satisfied with your changes after testing your scripts using rsync, you should commit the changes to your cookbook repositories and relaunch a fresh new server without the "development" tag (which is mentioned in more detail below).

Workflow using push and refetch

diag-Chef_Developer_Workflow_push-v2.png

Steps

Note: You must use this workflow if you are going to make any changes to the Chef metadata (e.g. Add a new recipe).

  1. Create a GitHub account and set up a working environment where you can push/pull changes between your local development machine and your GitHub repositories. See Create a New Cookbook Repository on GitHub
  2. Clone the ServerTemplate to create an editable version and name it accordingly. It's recommended that you commit the ServerTemplate before you make any changes, which will make it easier to track your changes against the original version.
  3. Go to the Scripts tab of the HEAD version (of the cloned ServerTemplate) and click Modify.
  4. Attach any new or modified cookbooks to the ServerTemplate. (Note: You can only attach one version of a cookbook to a ServerTemplate.)
  5. Add or change the list of scripts by adding new recipes or replacing old recipes with ones from your repository. 
  6. Create and launch a server with the HEAD version of the cloned ServerTemplate. It's important to use the HEAD version because you're likely going to change and test the ServerTemplate multiple times before you save your changes and commit the ServerTemplate to create a static revision. 
  7. Make a local change to a Chef cookbook/recipe and push the changes from your local development machine to your repository (e.g. GitHub). 
  8. The next step is to import the new and/or modified cookbooks from your repository (e.g. GitHub) into Repose (RightScale's mirror of your repositories) so that all of your changes can be used by ServerTemplates and Servers. See Refetch and Import a Repository.
  9. Wait for the refetch and import to be 100% completed.  You can monitor the status of the refresh action in the Events pane.
  10. In the RightScale dashboard, go to the running Server's Scripts tab and run the modified recipe.
  11. Check the Server's Audit Entries tab to verify that the script was executed successfully. 
  12. Repeat steps 3-10 each time you want to test a new script or code modification. 

Workflow using rsync

 

diag-Chef_Developer_Workflow_rsync-v2.png

Note: You can only use this workflow if you are not going to make any changes to the Chef metadata (e.g. Add a new recipe).

 

Steps

  1. Create a GitHub account and set up a working environment where you can push/pull changes to/from your local development machine to your GitHub repositories. See Create a New Cookbook Repository on GitHub
  2. Create a server with a HEAD version of ServerTemplate that is using Chef cookbooks and recipes for server configuration.  The cloud server will be used for developing and testing your scripts. 
  3. Under the Server's Info tab, add the following tag: rs_agent_dev:download_cookbooks_once=true
    The "download cookbooks once" tag tells the RightScale platform to only download the comma-separated list of cookbooks once from Repose (at launch time) instead of every time before a script is run (default with no tag). 
  4. Launch the server.   
  5. Modify a Chef cookbook or recipe. Instead of pushing the changes from your local development machine to your repository (e.g. GitHub) so that you can run and test the script on the running server, you can rsync the changes directly from your development machine to the running server instance in the cloud.
  6. Before you can run the rsync command, you will need to determine the unique repository ID for each repository that you're going to modify by SSHing into the running server instance.  See the Find a Cookbook UID section below.
  7. Use rsync to synchronize the cookbook directories on your local development machine and the cloud server instance.  You can either run the rsync command locally on either your development machine or instance, or create a script that will accomplish the same task.
  8. You can now run the modified script using 'rs_run_recipe' directly on the running server instance.  Open an SSH console session on the server instance and run the following command to view the logs in realtime as the script is run:
rs_run_recipe -n "<cookbook_name>::<recipe>" && tailf /var/log/messages
  1. Test and verify that the script was executed successfully. 
  2. Repeat steps 5-9 to test any further script modifications.  
  3. Once you are satisfied with all of your changes, commit and push the changes from your local development machine to your repository (e.g. GitHub). 
  4. Terminate the current development cloud server.
  5. The next step is to import the new or modified cookbooks from your repository (e.g. GitHub) into Repose (RightScale's mirror of your repositories) so that all of your changes can be used by ServerTemplates and Servers. See Refetch and Import a Repository
  6. Launch a new server instance using the HEAD ServerTemplate that reflects your latest code changes.
  7. Test the cloud server to make sure the scripts were run successfully.  Check the Server's Audit Entries tab for details.
  8. Commit the HEAD ServerTemplate to create a static and tested revision that you can use in a production environment.  Note: When you commit a HEAD ServerTemplate, the contents of the attached cookbooks becomes immutable. 

Find a Cookbook UID

When you launch a server that uses cookbooks for server configuration purposes, the required cookbooks are locally stored on the server instance itself. A unique identifier is assigned to each repository on a running server instance. You will need to know a repository's UID if you want to use the Chef Developer Workflow that uses rsync.  


Important!  A cookbook's UID is not static. A new UID will be associated to a cookbook each time you update a cookbook's version or "Refetch" the cookbook after updating its code in its source repository. 

 

Steps

Launch a server that uses cookbooks for server configuration purposes. 

Once the server is operational, SSH into the server instance and navigate to the directory where cookbooks are locally stored.  If you are using a server that was launched with a RightImage the cookbooks will be stored in the following location: /var/cache/rightscale/cookbooks/default

Run the following command to navigate to the default location:

# cd /var/cache/rightscale/cookbooks/default/

Each cookbook that is used by the server will be assigned a unique identifier.  Therefore, you will most likely see a list of several cookbook directories.

# cd /var/cache/rightscale/cookbooks/default/

# ls
05fe0e9401da911fdb518fe37b3a8c5393e3883d
12fdb518fe37b3a8c5393e3283d05fe0e9401da9
b518fe37b3a8c5193e3883d05fe0e9401da912fd

Inside each one you will find a 'cookbooks' directory with all of the repository's cookbooks and recipes.

# cd 05fe0e9401da911fdb518fe37b3a8c5393e3883d/cookbooks/

 

diag-CookbookStorage-v3.png

References

Command Line

If you want to run the command locally on your development machine, see code example below.

# rsync from Local Development Machine to Cloud Instance
#
# Assumes public key has been added to /root/.ssh/authorized_keys
#
# rsync -avz --exclude=.git <src_path> root@<instance>:/var/cache/rightscale/cookbooks/default/<HASH>
# where <scr_path> is the directory of where the cookbooks are locally stored on your development machine.
# <dst_path> is the directory of where the cookbooks are locally stored on the cloud server instance.
# <HASH> is the Cookbook UID.
# EXAMPLE:
rsync -avz --exclude=.git /src/cookbooks/ root@ec2-50-19-197-20.compute-1.amazonaws.com:/var/cache/rightscale/cookbooks/default/05fe0e9401da911fdb518fe37b3a8c5393e3883d/cookbooks

Ruby Script ('cbsync')

Use the cbsync Ruby script on your local development machine to rsync your current development directory to the cloud server (virtual machine) that you're using for testing purposes. Use the script to rsync one or all cookbooks.

See the 'psschroeter / cbsync' project: https://gist.github.com/psschroeter/6630949 

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Last Modified
10:58, 10 Dec 2013

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