In Jinja2 templates, it is often a good practice to test if a variable exists and what value does it carry.
There are several useful tests that you can make using Jinja2 builtin tests and filers.
In this article, i’ll show how to test if a variable exists or not, if it is empty or not and if it is set to True.
I’ll also give two examples of how to combine these checks. (more…)
What is Go? Go or Golang is a programming language created by Google in 2009 by Robert Griesemer, Rob Pike, and Ken Thompson.
Go language is designed for building simple, fast and reliable software.
In this tutorial i’ll show how to install Go on MacOS, Ubuntu, CentOS and how to create a simple “Hello world!” program on Golang. (more…)
What is Node Exporter? Node Exporter is a Prometheus exporter for hardware and OS metrics with pluggable metric collectors.
It allows to measure various machine resources such as memory, disk and CPU utilization.
In this article I’ll show how to install and configure Node Exporter on Ubuntu and CentOS using a systemd service manager. (more…)
What is Prometheus? Prometheus is an open-source monitoring and alerting software written in Go.
It collects metrics from configured targets and stores them in a local time series database.
Prometheus can run rules over collected data to either aggregate and record new time series from existing data or generate alerts.
To visualize the collected data Prometheus can be integrated with Grafana.
In the following article i will show how to install Prometheus using Docker on Ubuntu and CentOS. (more…)
What is Docker Compose? The docker-compose is a tool for defining and running complex multi-container Docker applications.
With docker-compose you can define a multi-container application in a single file, then spin your application up in a single command which does everything that needs to be done to get it running.
In this note i’ll show how to install, upgrade or uninstall docker-compose on Ubuntu, CentOS or MacOS using pip. (more…)
Each time you want to commit a bug or a feature, you need to create a branch for it.
To create a new branch there is a git branch command.
After you have created a branch, you need to switch in this branch using a git checkout command.
But it is also possible to create a new Git branch and switch in this branch using only one git checkout command with -b option. (more…)
When browser connects to a website, it includes a User-Agent string in its HTTP header.
Sometimes you may need to change User-Agent with curl to access some URL as a different browser.
This is a small note on how to set a custom User-Agent with curl from the command line in Linux. (more…)
Redis is a key-value database (also known as a key-value store) that uses a simple key/value method to store data.
Strings are the simplest data type in Redis and are simple key/value entries.
To save or fetch string data there are Redis SET and GET commands.
Redis SET command creates a key and assigns it some value (if the key already exists it just updates the value).
Redis GET command returns a value assigned to a key. (more…)
In Redis you can flush cache/database and delete all keys from all databases or from the particular database only using FLUSHALL and FLUSHDB commands.
To delete all keys from all Redis databases, use the FLUSHALL command.
To delete all keys of the selected Redis database only, use the FLUSHDB commnad. (more…)
There are two ways to get all keys from the all databases in Redis.
The first way is to list keys using --scan option and the second one is to get all keys using the KEYS command.
Note that the first way of getting all keys is preferable as it doesn’t require the client to load all the keys into memory despite of the KEYS command.
Use KEYS command only when the key space is reasonably sized. (more…)