=========================================
Spilo: HA PostgreSQL Clusters with Docker
Spilo is a Docker image that provides PostgreSQL and Patroni <https://github.com/zalando/patroni>__ bundled together. Patroni is a template for PostgreSQL HA. Multiple Spilos can create a resilient High Available PostgreSQL cluster. For this, you'll need to start all participating Spilos with identical etcd <https://github.com/coreos/etcd>__ addresses and cluster names.
Spilo's name derives from სპილო [spiːlɒ], the Georgian word for "elephant."
Real-World Usage and Plans
Spilo is currently evolving: Its creators are working on a Postgres operator that would make it simpler to deploy scalable Postgres clusters in a Kubernetes environment, and also do maintenance tasks. Spilo would serve as an essential building block for this. There is already a Helm chart <https://github.com/kubernetes/charts/tree/master/incubator/patroni>__ that relies on Spilo and Patroni to provision a five-node PostgreSQL HA cluster in a Kubernetes+Google Compute Engine environment. (The Helm chart deploys Spilo Docker images, not just "bare" Patroni.)
How to Use This Docker Image
Spilo's setup assumes that you've correctly configured a load balancer (HAProxy, ELB, Google load balancer) that directs client connections to the master. There are two ways to achieve this: A) if the load balancer relies on the status code to distinguish between the healthy and failed nodes (like ELB), then one needs to configure it to poll the API URL; otherwise, B) you can use callback scripts to change the load balancer configuration dynamically.
How to Build This Docker Image
$ cd postgres-appliance
$ docker build --tag $YOUR_TAG .
There are a few build arguments defined in the Dockerfile and it is possible to change them by specifying --build-arg arguments:
- WITH_PERL=false # set to true if you want to install perl and plperl packages into image
- PGVERSION="12"
- PGOLDVERSIONS="9.5 9.6 10 11"
- DEMO=false # set to true to build the smallest possible image which will work only on Kubernetes
- TIMESCALEDB_APACHE_ONLY=true # set to false to build timescaledb community version (Timescale License)
Run the image locally after build:
$ docker run -it your-spilo-image:$YOUR_TAG
Have a look inside the container:
$ docker exec -it $CONTAINER_NAME bash
Connecting to PostgreSQL
Administrative Connections
PostgreSQL is configured by default to listen to port 5432. Spilo master initializes PostgreSQL and creates the superuser and replication user (postgres and standby by default).
You'll need to setup Spilo to create a database and roles for your application(s). For example:
.. code-block:: bash
psql -h myfirstspilo.example.com -p 5432 -U admin -d postgres
Application Connections
Once you have created a database and roles for your application, you can connect to Spilo just like you want to connect to any other PostgreSQL cluster:
.. code-block:: bash
psql -h myfirstspilo.example.com -p 5432 -U wow_app -d wow
psql -d "postgresql://myfirstspilo.example.com:5432/wow?user=wow_app"
Configuration
Spilo is configured via environment variables, the values of which are either supplied manually via the environment (whenever Spilo is launched as a set of Docker containers) or added in the configuration file or manifest (whenever Spilo is used in the Docker orchestration environment, such as Kubernetes or Docker Compose).
Please go here <https://github.com/zalando/spilo/blob/master/ENVIRONMENT.rst>__ to see our list of environment variables.
To supply env variables manually via the environment for local testing:
docker run -it -e YOUR_ENV_VAR=test your-spilo-image:latest
Issues and Contributing
Spilo welcomes questions via our issues tracker <https://github.com/zalando/spilo/issues>. We also greatly appreciate fixes, feature requests, and updates; before submitting a pull request, please visit our contributor guidelines <https://github.com/zalando/spilo/blob/master/CONTRIBUTING.rst>.
License
This project uses the Apache 2.0 license <https://github.com/zalando/spilo/blob/master/LICENSE>__.