Fedora uses a set of staging servers for several purposes:
When applications are initially being deployed, the staging version of those applications are setup with a staging server that is used to create the initial Ansible configuration for the application/service.
Established applications/services use staging for testing. This testing includes:
Configuration changes managed by Ansible
Upstream updates to dependent packages (httpd changes for example)
The staging servers should be self contained and have all the needed databases and such to function. At no time should staging resources talk to production instances. We use firewall rules on our production servers to make sure no access is made from staging.
Staging instances do often use dumps of production databases and data, and thus access to resources in staging should be controlled as it is in production.
DNS and naming
All staging servers should be in the
/etc/hosts files are used on stg servers to override dns in
cases where staging resources should talk to the staging version of a
service instead of the production one. In some cases, one staging server
may be aliased to several services or applications that are on different
machines in production.
Sometimes you want to resync the staging fas server with what’s on production. To do that, dump what’s in the production db and then import it into the staging db. Note that resyncing the information will remove any of the information that has been added to the staging fas servers. So it’s good to mention that you’re doing this on the infra list or to people who you know are working on the staging fas servers so they can either save their changes or ask you to hold off for a while.
$ ssh db01 $ sudo -u postgres pg_dump -C fas2 |xz -c fas2.dump.xz $ scp fas2.dump.xz db02.stg:
On fas01.stg (postgres won’t drop the database if something is accessing it) (ATM, fas in staging is not load balanced so we only have to do this on one server):
$ sudo /etc/init.d/httpd stop
$ echo 'drop database fas2' |sudo -u postgres psql $ xzcat fas2.dump.xz | sudo -u postgres psql
$ sudo /etc/init.d/httpd start
Other databases behave similarly.
There is http/https access from the internet to staging instances to allow testing. Simply replace the production resource domain with stg.fedoraproject.org and it should go to the staging version (if any) of that resource.
Ansible and Staging
All staging machine configurations is now in the same branch as master/production.
There is a 'staging' environment - Ansible variable "env" is equal to "staging" in playbooks for staging things. This variable can be used to differentiate between producion and staging systems.
Workflow for staging changes
If you don’t need to make any Ansible related config changes, don’t do anything. (ie, a new version of an app that uses the same config files, etc). Just update on the host and test.
If you need to make Ansible changes, either in the playbook of the application or outside of your module:
Make use of files ending with .staging (see resolv.conf in global for an example). So, if there’s persistent changes in staging from production like a different config file, use this.
Conditionalize on environment:
- name: your task ... when: env == "staging" - name: production-only task ... when: env != "staging"
These changes can stay if they are helpful for further testing down the road. Ideally normal case is that staging and production are configure in the same host group from the same Ansible playbook.
Time limits on staging changes
There is no hard limit on time spent in staging, but where possible we should limit the time in staging so we are not carrying changes from production for a long time and possible affecting other staging work.
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