States tutorial, part 4¶

Note

This tutorial builds on topics covered in part 1, part 2 and part 3. It is recommended that you begin there.

This part of the tutorial will show how to use salt's file_roots to set up a workflow in which states can be "promoted" from dev, to QA, to production.

Salt fileserver path inheritance¶

Salt's fileserver allows for more than one root directory per environment, like in the below example, which uses both a local directory and a secondary location shared to the salt master via NFS:

# In the master config file (/etc/salt/master)
file_roots:
  base:
    - /srv/salt
    - /mnt/salt-nfs/base

Salt's fileserver collapses the list of root directories into a single virtual environment containing all files from each root. If the same file exists at the same relative path in more than one root, then the top-most match "wins". For example, if /srv/salt/foo.txt and /mnt/salt-nfs/base/foo.txt both exist, then salt://foo.txt will point to /srv/salt/foo.txt.

Note

When using multiple fileserver backends, the order in which they are listed in the fileserver_backend parameter also matters. If both roots and git backends contain a file with the same relative path, and roots appears before git in the fileserver_backend list, then the file in roots will "win", and the file in gitfs will be ignored.

A more thorough explanation of how Salt's modular fileserver works can be found here. We recommend reading this.

Environment configuration¶

Configure a multiple-environment setup like so:

file_roots:
  base:
    - /srv/salt/prod
  qa:
    - /srv/salt/qa
    - /srv/salt/prod
  dev:
    - /srv/salt/dev
    - /srv/salt/qa
    - /srv/salt/prod

Given the path inheritance described above, files within /srv/salt/prod would be available in all environments. Files within /srv/salt/qa would be available in both qa, and dev. Finally, the files within /srv/salt/dev would only be available within the dev environment.

Based on the order in which the roots are defined, new files/states can be placed within /srv/salt/dev, and pushed out to the dev hosts for testing.

Those files/states can then be moved to the same relative path within /srv/salt/qa, and they are now available only in the dev and qa environments, allowing them to be pushed to QA hosts and tested.

Finally, if moved to the same relative path within /srv/salt/prod, the files are now available in all three environments.

Practical Example¶

As an example, consider a simple website, installed to /var/www/foobarcom. Below is a top.sls that can be used to deploy the website:

/srv/salt/prod/top.sls:

base:
  'web*prod*':
    - webserver.foobarcom
qa:
  'web*qa*':
    - webserver.foobarcom
dev:
  'web*dev*':
    - webserver.foobarcom

Using pillar, roles can be assigned to the hosts:

/srv/pillar/top.sls:

base:
  'web*prod*':
    - webserver.prod
  'web*qa*':
    - webserver.qa
  'web*dev*':
    - webserver.dev

/srv/pillar/webserver/prod.sls:

webserver_role: prod

/srv/pillar/webserver/qa.sls:

webserver_role: qa

/srv/pillar/webserver/dev.sls:

webserver_role: dev

And finally, the SLS to deploy the website:

/srv/salt/prod/webserver/foobarcom.sls:

{% if pillar.get('webserver_role', '') %}
/var/www/foobarcom:
  file.recurse:
    - source: salt://webserver/src/foobarcom
    - env: {{ pillar['webserver_role'] }}
    - user: www
    - group: www
    - dir_mode: 755
    - file_mode: 644
{% endif %}

Given the above SLS, the source for the website should initially be placed in /srv/salt/dev/webserver/src/foobarcom.

First, let's deploy to dev. Given the configuration in the top file, this can be done using state.apply:

salt --pillar 'webserver_role:dev' state.apply

However, in the event that it is not desirable to apply all states configured in the top file (which could be likely in more complex setups), it is possible to apply just the states for the foobarcom website, by invoking state.apply with the desired SLS target as an argument:

salt --pillar 'webserver_role:dev' state.apply webserver.foobarcom

Once the site has been tested in dev, then the files can be moved from /srv/salt/dev/webserver/src/foobarcom to /srv/salt/qa/webserver/src/foobarcom, and deployed using the following:

salt --pillar 'webserver_role:qa' state.apply webserver.foobarcom

Finally, once the site has been tested in qa, then the files can be moved from /srv/salt/qa/webserver/src/foobarcom to /srv/salt/prod/webserver/src/foobarcom, and deployed using the following:

salt --pillar 'webserver_role:prod' state.apply webserver.foobarcom

Thanks to Salt's fileserver inheritance, even though the files have been moved to within /srv/salt/prod, they are still available from the same salt:// URI in both the qa and dev environments.

Continue Learning¶

The best way to continue learning about Salt States is to read through the reference documentation and to look through examples of existing state trees. Many pre-configured state trees can be found on Github in the saltstack-formulas collection of repositories.

If you have any questions, suggestions, or just want to chat with other people who are using Salt, we have a very active community and we'd love to hear from you.

In addition, by continuing to part 5, you can learn about the powerful orchestration of which Salt is capable.