VM disk performance across datastores
Here are some disk performance measurements (made on a Windows 10 VM on vSphere 6.5 with CrystalDiskMark) across different types of datastore (local SSD array, NFS (sync), NFS (async) and… Read more »
Author Archives: roger
Blocking access to an ip address
Sometimes you need to block access to a specific ip address for test purposes – for instance to simulate unavailability of a web-service. Here’s how to do it on macOS… Read more »
Moving Docker container data
If you have created a container without specifying a volume, Docker will create one for you. If you later decide you’d rather have the container’s data somewhere else, you can… Read more »
Repairing a broken Postgres-BDR cluster
Postgres-BDR is an excellent multi-master replication clustering extension for PostgreSQL (https://www.2ndquadrant.com/en/resources/postgres-bdr-2ndquadrant/). We often use it for fault tolerant systems – its asynchronous and uncomplicated to set up (at least if… Read more »
A contact-tracing armband
Current plans for contact-tracing are based around mobile phones, because these have built-in capabilities for location tracking and contact detection. An alternative to mobile phones for contact-tracing would be a… Read more »
The role of statistical scoring models in contact-tracing
Each contact you have with another person potentially infects you with a virus. If the person you have contact with later tests positive for that virus, the contact you had… Read more »
An API-first approach to COVID-19 contact-tracing
Contact-tracing is one of the most useful tools in the fight to control the spread of a virus. Authorities in China, Singapore and South Korea have successfully deployed contact-tracing as… Read more »
API rate-limiting with HAProxy
We typically deploy REST APIs behind a HAProxy reverse proxy. We often need to enforce SLAs and protect those APIs from being flooded with too many concurrent requests. In this… Read more »
Minimal web server docker containers
Introduction We often need a simple web server as a Docker container to serve up static content (HTML or an Angular app etc) or a minimal php web app. So… Read more »
Designing REST APIs – lessons learnt
Introduction We’ve been designing and deploying micro-services with REST APIs for a while now, using API-First design. Time to document some of the lessons we’ve learnt during that process. They’re… Read more »