Server Provisioning¶
Overview¶
School_Inspector is deployed on the following stack.
- OS: Ubuntu 12.04 LTS
- Python: 3.4
- Database: Postgres 9.1
- Application Server: Gunicorn
- Frontend Server: Nginx
- Cache: Memcached
These services can configured to run together on a single machine or on different machines. Supervisord manages the application server process.
Initial Setup¶
Before your project can be deployed to a server, the code needs to be accessible in a git repository. Once that is done you should update conf/pillar/<environment>/env.sls to set the repo and branch for the environment. E.g., change this:
# FIXME: Update to the correct project repo
repo:
url: git@github.com:CHANGEME/CHANGEME.git
branch: master
to this:
repo:
url: git@github.com:codefordurham/school-inspector.git
branch: master
The repo will also need a deployment key generated so that the Salt minion can access the repository. You can generate a deployment key locally for the new server like so:
ssh-keygen -t rsa -b 4096 -f <servername>
This will generate two files named <servername> and <servername>.pub. The first file contains the private key and the second file contains the public key. The public key needs to be added to the “Deploy keys” in the GitHub repository. For more information, see the Github docs on managing deploy keys: https://help.github.com/articles/managing-deploy-keys
The text in the private key file should be added to conf/pillar/<environment>/secrets.sls` under the label github_deploy_key, e.g.:
github_deploy_key: |
-----BEGIN RSA PRIVATE KEY-----
foobar
-----END RSA PRIVATE KEY-----
There will be more information on the secrets in a later section. You may choose to include the public SSH key inside the repo itself as well, but this is not strictly required.
You also need to set project_name and python_version in conf/pillar/project.sls. Currently we support using Python 2.7 or Python 3.3. The project template is set up for 2.7 by default. If you want to use 3.3, you will need to change python_version and make a few changes to requirements. In requirements/production.txt, change python-memcached to python3-memcached. In requirements/dev.txt, remove Fabric and all its dependencies. Instead you will need Fabric installed on your laptop “globally” so that when you run fab, it will not be found in your virtualenv, but will then be found in your global environment.
For the environment you want to setup you will need to set the domain in conf/pillar/<environment>/env.sls.
You will also need add the developer’s user names and SSH keys to conf/pillar/devs.sls. Each user record (under the parent users: key) should match the format:
example-user:
public_key:
- ssh-rsa <Full SSH Public Key would go here>
Additional developers can be added later, but you will need to create at least one user for yourself.
Managing Secrets¶
Secret information such as passwords and API keys should never be committed to the source repository. Instead, each environment manages its secrets in conf/pillar/<environment>/secrets.sls. These secrets.sls files are excluded from the source control and need to be passed to the developers out of band. There are example files given in conf/pillar/<environment>/secrets.ex. They have the format:
secrets:
DB_PASSWORD: XXXXXX
Each key/value pair given in the secrets dictionary will be added to the OS environment and can retrieved in the Python code via:
import os
password = os.environ['DB_PASSWORD']
Secrets for other environments will not be available. That is, the staging server will not have access to the production secrets. As such there is no need to namespace the secrets by their environment.
Environment Variables¶
Other environment variables which need to be configured but aren’t secret can be added to the env dictionary in conf/pillar/<environment>/env.sls:
# Additional public environment variables to set for the project env:
FOO: BAR
For instance the default layout expects the cache server to listen at 127.0.0.1:11211 but if there is a dedicated cache server this can be changed via CACHE_HOST. Similarly the DB_HOST/DB_PORT defaults to ''/'':
env:
DB_HOST: 10.10.20.2
CACHE_HOST: 10.10.20.1:11211
Setup Checklist¶
To summarize the steps above, you can use the following checklist
- repo is set in conf/pillar/<environment>/env.sls
- Developer user names and SSH keys have been added to conf/pillar/devs.sls
- Project name has been set in conf/pillar/project.sls
- Environment domain name has been set in conf/pillar/<environment>/env.sls
- Environment secrets including the deploy key have been set in conf/pillar/<environment>/secrets.sls
Salt Master¶
Each project needs to have at least one Salt Master. There can be one per environment or a single Master which manages both staging and production. The master is configured with Fabric. You will need to be able to connect to the server as a root user. How this is done will depend on where the server is hosted. VPS providers such as Linode will give you a username/password combination. Amazon’s EC2 uses a private key. These credentials will be passed as command line arguments.:
# Template of the command
fab -H <fresh-server-ip> -u <root-user> setup_master
# Example of provisioning 33.33.33.10 as the Salt Master
fab -H 33.33.33.10 -u root setup_master
# Example DO setup
fab -H 107.170.136.182 -u root setup_master
# Example AWS setup
fab -H 54.86.14.136 -u ubuntu -i ~/.ssh/aws-cfa.pem setup_master
This will install salt-master and update the master configuration file. The master will use a set of base states from https://github.com/caktus/margarita using the gitfs root. Once the master has been provisioned you should set:
env.master = '<ip-of-master>'
in the top of the fabfile.
If each environment has its own master then it should be set with the environment setup function staging or production. In these case most commands will need to be preceded with the environment to ensure that env.master is set.
Additional states and pillar information are contained in this repo and must be rsync’d to the master via:
fab -u <root-user> sync
This must be done each time a state or pillar is updated. This will be called on each deploy to ensure they are always up to date.
To provision the master server itself with salt you need to create a minion on the master:
fab -H <ip-of-new-master> -u <root-user> --set environment=master setup_minion:salt-master
fab -u <root-user> accept_key:<server-name>
fab -u <root-user> --set environment=master deploy
# Example DO (may have to run a second time to catch key)
fab -H 107.170.136.182 -u root --set environment=master setup_minion:salt-master
fab -H 107.170.136.182 -u root --set environment=master deploy
# Example AWS setup
fab -H 54.86.14.136 -u ubuntu -i ~/.ssh/aws-cfa.pem --set environment=master setup_minion:salt-master
fab -H 54.86.14.136 -u ubuntu -i ~/.ssh/aws-cfa.pem --set environment=master deploy
This will create developer users on the master server so you will no longer have to connect as the root user.
Provision a Minion¶
Once you have completed the above steps, you are ready to provision a new server for a given environment. Again you will need to be able to connect to the server as a root user. This is to install the Salt Minion which will connect to the Master to complete the provisioning. To setup a minion you call the Fabric command:
fab <environment> setup_minion:<roles> -H <ip-of-new-server> -u <root-user>
fab staging setup_minion:web,balancer,db-master,cache -H 33.33.33.10 -u root
# Example DO
fab production setup_minion:web,balancer,db-master,cache,queue,worker -H 107.170.136.182
# Example AWS setup
fab production setup_minion:web,balancer,db-master,cache,queue,worker -H 54.86.14.136
The available roles are salt-master, web, worker, balancer, db-master, queue and cache. If you are running everything on a single server you need to enable the web, balancer, db-master, and cache roles. The worker and queue roles are only needed to run Celery which is explained in more detail later.
Additional roles can be added later to a server via add_role. Note that there is no corresponding delete_role command because deleting a role does not disable the services or remove the configuration files of the deleted role:
fab add_role:web -H 33.33.33.10
After that you can run the deploy/highstate to provision the new server:
fab <environment> deploy
The first time you run this command, it may complete before the server is set up. It is most likely still completing in the background. If the server does not become accessible or if you encounter errors during the process, review the Salt logs for any hints in /var/log/salt on the minion and/or master. For more information about deployment, see the server setup </server-setup> documentation.
Optional Configuration¶
The default template contains setup to help manage common configuration needs which are not enabled by default.
HTTP Auth¶
The secrets.sls can also contain a section to enable HTTP basic authentication. This is useful for staging environments where you want to limit who can see the site before it is ready. This will also prevent bots from crawling and indexing the pages. To enable basic auth simply add a section called http_auth in the relevant conf/pillar/<environment>/secrets.sls:
http_auth:
admin: 123456
This should be a list of key/value pairs. The keys will serve as the usernames and the values will be the password. As with all password usage please pick a strong password.
Celery¶
Many Django projects make use of Celery for handling long running task outside of request/response cycle. Enabling a worker makes use of Django setup for Celery. As documented you should create/import your Celery app in school_inspector/__init__.py so that you can run the worker via:
celery -A school_inspector worker
Additionally you will need to configure the project settings for Celery:
# school_inspector.settings.staging.py
import os
from school_inspector.settings.base import *
# Other settings would be here
BROKER_URL = 'amqp://school_inspector_staging:%(BROKER_PASSWORD)s@%(BROKER_HOST)s/school_inspector_staging' % os.environ
You will also need to add the BROKER_URL to the school_inspector.settings.production so that the vhost is set correctly. These are the minimal settings to make Celery work. Refer to the Celery documentation for additional configuration options.
BROKER_HOST defaults to 127.0.0.1:5672. If the queue server is configured on a separate host that will need to be reflected in the BROKER_URL setting. This is done by setting the BROKER_HOST environment variable in the env dictionary of conf/pillar/<environment>/env.sls.
To add the states you should add the worker role when provisioning the minion. At least one server in the stack should be provisioned with the queue role as well. This will use RabbitMQ as the broker by default. The RabbitMQ user will be named school_inspector_<environment> and the vhost will be named school_inspector_<environment> for each environment. It requires that you add a password for the RabbitMQ user to each of the conf/pillar/<environment>/secrets.sls:
secrets:
BROKER_PASSWORD: thisisapasswordforrabbitmq
The worker will run also run the beat process which allows for running periodic tasks.