A little companion for your Postgres HA deployment on Kubernetes that labels its pods with the current replication role
If you have played with Postgres in HA, having several primary servers, you probably know Replication Manager. This tool keeps 'primary' and 'standby' nodes synchronized and promotes 'standby' to 'primary' on failures.
This commonly implies having a proxy in front of all Postgres nodes to route writing operations to 'primary', balance reading operations to the rest of nodes, and other advantages.
This proxy-pattern helps to mask failures in a way the client application commonly doesn't notice, being super useful in huge productive customer-facing systems.
But what happens if you require HA on smaller systems? Is the overhead of configuring perfect proxy worth? The answer is NO.
Replication Manager is taking care of your Postgres, so you always have a 'primary' available. But Kubernetes cannot distinguish the role of your nodes, or it can?
This application is a little CLI that checks the roles of your Postgres Pods from time to time, and labels them with the role.
This way you can create a Kubernetes Service that points always to the 'primary' deleting the need of a complicated proxy on small HA deployments
Every configuration parameter can be defined by flags that can be passed to the CLI. They are described in the following table:
| Name | Description | Default | Example |
|---|---|---|---|
--log-level |
Define the verbosity of the logs | info |
--log-level info |
--disable-trace |
Disable traces from logs | false |
--disable-trace true |
--kubeconfig |
Path to kubeconfig | - |
--kubeconfig="~/.kube/config" |
--disable-services-creation |
Disable the creation of the services | false |
--disable-services-creation=true |
--sync-time |
Synchronization time in seconds | 5s |
--sync-time=2m |
Security-critical parameters are managed by environment variables. They are described in the following table:
| Name | Description | Default | Example |
|---|---|---|---|
PG_CONNECTION_STRING |
OBDC styled connection string | - |
postgresql://username:password@hostname.com:5432/db |
Here you have a complete example to use this command.
Output is thrown always in JSON as it is more suitable for automations
export PG_CONNECTION_STRING="postgresql://username:password@hostname.com:5432/db"
pg-selector run \
--log-level=info
--kubeconfig="./path"ATTENTION: If you detect some mistake on the examples, open an issue to fix it. This way we all will benefit
This project provides binary files and Docker images to make it easy to use wherever wanted
Binary files for the most popular platforms will be added to the releases
Docker images can be found in GitHub's packages related to this repository
Do you need it in a different container registry? We think this is not needed, but if we're wrong, please, let's discuss it in the best place for that: an issue
We are open to external collaborations for this project: improvements, bugfixes, whatever.
For doing it, open an issue to discuss the need of the changes, then:
- Fork the repository
- Make your changes to the code
- Open a PR and wait for review
The code will be reviewed and tested (always)
We are developers and hate bad code. For that reason, we ask you the highest quality on each line of code to improve this project on each iteration.
Copyright 2022.
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
This project was done using IDEs from JetBrains. They helped us to develop faster, so we recommend them a lot! 🤓
