PyWPS Ansible Playbook

Use Ansible to deploy a full-stack PyWPS service.

Warning

This playbook is under development and is currently only used to deploy PyWPS applications from Birdhouse like Emu.

Warning

The current version (>= v0.6.0) is a major update of the Ansible deployment. It includes a role to deploy Slurm. It can only be used for a single host deployment.

The deployment on a Slurm cluster is only support by the previous version v0.5.x.

Introduction

PyWPS Ansible Playbook can completely provision a server to run the full stack of PyWPS, including:

• Conda to manage application dependencies.
• Nginx as Web-Server.
• Supervisor to start/stop and monitor services.
• PostgreSQL optional database used for job logging.
• Slurm optional workload manager for jobs.

It will install a PyWPS application on a single host. Nginx, Supervisor and miniconda are installed on the system. The PyWPS application is fetched from GitHub and dependencies are installed into a Conda environment.

Testing with Vagrant

Use Vagrant to test the installation:

vagrant up

Login in to VM:

vagrant ssh

Become root:

sudo -i 

Install ansible:

dnf install epel-release
dnf install ansible

Change to the /vagrant folder:

cd /vagrant

Configure the playbook:

cp etc/sample-vagrant.yml custom.yml
vim custom.yml

Run the playbook:

make play

Check if WPS is running:

supervisorctl status

Check WPS service by getting the capabilities:

http://192.168.128.100/wps?service=wps&version=1.0.0&request=GetCapabilities

Configuration

Edit custom.yml

You need to customize the Ansible deployment configuration to install your PyWPS service. Create a custom.yml configuration and overwrite any of the variables found in group_vars/all. There are some prepared sample configurations etc/sample-*.yml for specific deployments. Copy one of those to get started.

You can also add your custom configurations to the etc/ folder to stay away from Git control:

$ cp etc/sample-emu.yml etc/custom-emu.yml
$ vim etc/custom-emu.yml
$ ln -s etc/custom-emu.yml custom.yml

Use Conda to build identical environments

You can use Conda specification files to build identical environments. The WPS service needs to have a specification file, spec-file.txt, in its top level folder. You can set the following option in your custom.yml:

conda_env_use_spec: true

See an example in etc/sample-emu-with-conda-spec.yml.

Warning

This is option is currently enabled for [all]{.title-ref} configured WPS services.

Use sqlite Database

You can use a SQLite database with the following settings:

db_install_postgresql: false
db_install_sqlite: true

See an example in etc/sample-sqlite.yml.

Use PostgreSQL Database installed by playbook

By default the playbook will install a PostgreSQL database. You can customize the installation. For example you can configure a database user:

db_user: dbuser
db_password: dbuser

See an example in etc/sample-postgres.yml.

Use external PostgreSQL Database

If you want to use an existing database you can skip the database installation by setting the variable:

db_install_postgresql: false

You need to configure then the database connection string to your external database:

wps_database: "postgresql+psycopg2://user:password@host:5432/pywps"

See an example in etc/sample-postgres.yml.

Install multiple PyWPS applications

You can install several PyWPS applications with a single Ansible run. See etc/sample-multiple.yml configuration as example.

You can also configure a shared file-server for outputs. See etc/sample-multiple-with-shared-fileserver.yml.

Use HTTPS with Nginx

You can enable HTTPS for the Nginx service by setting the variable:

wps_enable_https: true

See etc/sample-certs.yml configuration as example.

By default it generates a self-signed certificate automatically.

You can also provide your own certificate by setting the following variables:

ssl_certs_local_privkey_path: '/path/to/example.com.key'
ssl_certs_local_cert_path: '/path/to/example.com.pem'

Read the ssl-certs role documentation for details.

Extend PyWPS configuration

This Ansible playbook has its own template for a PyWPS configuration file. This template does not cover all options and you might want to extend it for additional configurations. You can extend the pywps.cfg configuration with the extra_config option. Here is an example:

---
server_name: demowps
wps_services:
  - name: demo
    hostname: "{{ server_name }}"
    port: 5000
    extra_config: |
      [data]
      cache_path = /tmp/cache