Category: Systems Admin

  • How to Replace Characters in MongoDB

    TL; DR: As of MongoDB 6.0, this is how I learned to replace some characters in a field in all documents. In the example below all “.” characters in field_name will be replaced by “_” character: The backstory is when using MongoDB with MongoEngine, there’s an issue when a key in a dictionary field contains […]

  • Sample Terraform Code to Manage Temporary Access to GCP

    TL; DR: This is a way to grant a temporary access to some GCP resources using Terraform’s time_static and google_project_iam_member resources. 🙂

  • Solved: Uninstallation of config-connector Got Stuck in ArgoCD

    The Kubernetes Config Connector is another level of IaC(Infrastructure as Code): It wraps Google Cloud resources like a Cloud Load Balancer with Kubernetes CRDs(Custom Resource Definition) so instead of writing Terraform HCL I can write YAML to manage GCP infrastructure. However when there’s a need to uninstall a config-connector, it got stuck in ArgoCD As […]

  • Django DB Migration Job with ArgoCD

    A Job in Kubernetes is a one-off and immutable task to be carried out during deployment. But what if a job needs to run for each deployment? A new job with the same name can’t be deployed on top of the existing one, given it in completed or failed state. Since Kubernetes 1.23, A TTL(Time […]

  • How to Query in MongoDB and Group by Date

    TL;DR: Here’s a quick example to query MongoDB documents created this year(2023) and group them by date, ie. how many my_doc were created today, yesterday, the day before yesterday, etc. The following statement works in a MongoDB client such as mongosh. Then here’s an equivalent example to do it with MongoEngine in Python: Since I […]

  • Cloud SQL MySQL: Best Password is No Password

    Security for web applications has come a long way. In the case of database passwords, there is a lot of approaches to keep them safe: But isn’t it the best if there’s no need for a password at all? With IAM authentication for Cloud SQL, the password can be avoided after all. Here’s how to […]

  • How to Self-Host a Mastodon Instance in Kubernetes

    TL;DR: Instead of the official installation including setting up Ruby, nginx, systemd service, etc., I found it more comfortable to install and run a Mastodon instance using some YAML files. Just in case, what is Mastodon anyway? I used kustomize to manage and generate Kubernetes manifests for a fully functional Mastodon instance. Please see my […]

  • A Simple RabbitMQ Consumer with Python

    Here’s a very simple RabbitMQ consumer in Python, deployed in a Kubernetes cluster. I used this to act as a consumer for testing purposes. First the Python code: The above code can be saved as a ConfigMap in the cluster: Then the Kubernetes manifest: At last this can be simply deployed with 🙂