Fabian Lee : Software Engineer

Kubernetes: HorizontalPodAutoscaler evaluation based on Prometheus metric

September 9, 2023
Categories: Kubernetes, Monitoring

HorizontalPodAutoscaler (HPA) allow you to dynamically scale the replica count of your Deployment based on basic CPU/memory resource metrics from the metrics-server. If you want scaling based on more advanced scenarios and you are already using the Prometheus stack, the prometheus-adapter provides this enhancement. The prometheus-adapter takes basic Prometheus metrics, and then synthesizes custom API … Kubernetes: HorizontalPodAutoscaler evaluation based on Prometheus metric

Kubernetes: custom upstream for domain with CoreDNS

August 1, 2022
Categories: Kubernetes

If you have a domain that you want CoreDNS to forward to a specific upstream DNS, you can add a block to the CoreDNS configmap. Adding this domain block to the CoreDNS configmap and restarting the CoreDNS pods is sufficient will make the change take affect. You may need to restart client pods if DNS … Kubernetes: custom upstream for domain with CoreDNS

Kubernetes: independent resolv.conf for CoreDNS with K3s

August 1, 2022
Categories: Kubernetes

The default setting for pod DNS resolution has CoreDNS use the settings from the underlying OS of the worker node. If your Kubernetes VMs are joined to multiple networks or search domains, this can cause unexpected results as well as performance issues. If you are using K3s, you can provide an independent resolv.conf file for … Kubernetes: independent resolv.conf for CoreDNS with K3s

Kubernetes: independent resolv.conf for CoreDNS with kubeadm

August 1, 2022
Categories: Kubernetes

The default setting for pod DNS resolution has CoreDNS use the settings from the underlying OS of the worker node. If your Kubernetes VMs are joined to multiple networks or search domains, this can cause unexpected results as well as performance issues. If you are using kubeadm, you can provide an independent resolv.conf file for … Kubernetes: independent resolv.conf for CoreDNS with kubeadm

Prometheus: monitoring a custom Service using ServiceMonitor and PrometheusRule

July 7, 2022
Categories: Kubernetes, Monitoring

If you are running the Prometheus Operator as part of your monitoring stack (e.g. kube-prometheus-stack) then you can have your custom Service monitored by defining a ServiceMonitor CRD. The ServiceMonitor is an object that defines the service endpoints that should be scraped by Prometheus and at what interval. In this article, we will deploy a … Prometheus: monitoring a custom Service using ServiceMonitor and PrometheusRule

Kubernetes: liveness probe for Spring Boot with custom Actuator health check

June 30, 2022
Categories: Java, Kubernetes

A Kubernetes liveness and readiness probe is how the kubelet determines health of a pod. This is often times as simple as checking the ability to reach the main service port over TCP or HTTP. But if you are using Spring Boot and have enabled the Actuator dependency, you have the ability to create even … Kubernetes: liveness probe for Spring Boot with custom Actuator health check

Java: Adding custom metrics to Spring Boot Micrometer Prometheus endpoint

June 29, 2022
Categories: Development, Java

If you have enabled Actuator and the ‘micrometer-registry-prometheus’ dependency in your Spring Boot application, then you will have a new ‘/actuator/prometheus’ web endpoint that returns general information about threads, garbage collection, disk, and memory. This information is delivered in standard prometheus formatting as plaintext, with one metric per line. This is exactly the type of … Java: Adding custom metrics to Spring Boot Micrometer Prometheus endpoint

Ansible: creating SAN certificates with a custom root CA

April 5, 2021
Categories: Automation

Ansible has support for generating self-signed certificates as well as certificates using a custom root CA (certificate authority). This is possible using the community.crypto collection. I’ve put this into a role named ansible-role-cert-with-ca available on github, and it can be used from a playbook like below: vars: # custom CA, leaving undefined will create self-signed … Ansible: creating SAN certificates with a custom root CA

Ubuntu: Adding a root certificate authority

March 27, 2020
Categories: Linux

If your backend components or application servers use a custom CA (Certificate Authority), then you may need to add it to the system trusted root certificate store so that the standard tools and other utilities trust the TLS communication.

KVM: Building the latest OVMF firmware for virtual machines

September 12, 2018
Categories: Linux

OVMF is an open-source project that implements the Unified Extensible Firmware Interface (UEFI) specification. UUEFI is designed to eventually replace the BIOS firmware interface. In this article, I will show how to build the latest OVMF image from source.

Java: Using XMLAdapter to process custom datatypes using JAXB

February 2, 2018
Categories: Java

JAXB provides a framework for two-way binding between XML and Java structures, making it easy for developers to serialize and deserialize their XML into Java objects. Decorating a class with @XmlElement and @XmlAttribute annotations is all it usually takes to build a rich domain model from XML, but sometimes you get into a situation where … Java: Using XMLAdapter to process custom datatypes using JAXB

Ubuntu: Enabling syslog on Ubuntu and custom templates

May 24, 2017
Categories: Linux, Logging

Syslog is a message logging standard has been around for decades, but has renewed popularity as a method of log capture with the advent of containerization and centralized logging solutions. Enabling an Ubutu 14.04 or 16.04 host to act as a syslog server only takes a few simple steps.

ELK: Custom template mappings to force field types

May 2, 2017
Categories: Logging

It is very common to have Logstash create time-based indexes in ElasticSearch that fit the format, <indexName>-YYYY.MM.DD. This means events submitted with @timestamp for that day all go to the same index. However, if you do not explicitly specify an index template that maps each field to a type, you can end up with unexpected query … ELK: Custom template mappings to force field types

Nginx: Custom access log format and error levels

February 14, 2017
Categories: Linux

Nginx is a powerful application level proxy server. Whether for troubleshooting or analysis, enabling log levels and custom formats for the access/error logs is a common requirement. Error Logs By default, only messages in the error category are logged. If you want to enable more details, then modify nginx.conf like: error_log file [level] Enabling debug … Nginx: Custom access log format and error levels

SaltStack: Creating a Custom Grain using Python

October 5, 2016
Categories: DevOps, Python

SaltStack grains are used for relatively static information such as operating system, IP address, and other system properties. They are also useful for targeting minions, for example whether a system is part of dev/test/prod, or a flag on whether it falls under LifeScience or HIPAA regulation. In this article we will implement a custom grain … SaltStack: Creating a Custom Grain using Python

EMC OnDemand: Best Practices for Custom Methods

February 24, 2013
Categories: Documentum

The concept of custom methods which run directly on the Java Method Server has proven an extremely useful extension point for Documentum developers and solutions architects. Whether used in a workflow activity to integrate with an enterprise message queue or as an action for Webtop users who need temporarily escalated privileges to apply legal retention, … EMC OnDemand: Best Practices for Custom Methods