In part 1 of this series, I introduced Prometheus and lay some foundations for monitoring a Sitecore container environment using Prometheus. In this post, I will show you how to collect and monitor the Host OS and container metrics exposed by Docker.
Why should we care about Docker the Host OS Metrics?
To monitor your containerized Sitecore application effectively you need to understand the health of the underlying system your containers are running on. To achieve this, you have to monitor the system metrics like CPU, memory, network, and disk also docker is starting and stopping containers so you need to know the state of your docker resource.
How to collect Docker performance metrics
Docker supports Prometheus OOTB and provides performance metrics you can collect and monitor, however it is disabled by default.
1. Enabling Docker Metrics.
First things first lets enable the metrics. Open the daemon.json file and add the metrics-address setting:
“metrics-addr” : “127:0:0:1:9323”
Apply and restart docker. Now you should be able browse to the docker metrics 127.0.0.1:9323/metrics and verify metrics are exposed.
In a previous post I provided you with some techniques to help you monitor your Containerized Sitecore instance using native tools. Over the next few posts, I will show some of the common tools and techniques used for monitoring applications running in containers. When I initially started thinking about this I considered using InfluxDB as my time series DB to store the performance metrics and Grafana for visualizing and alerting. As both of these were already in my tool-set for load testing. However, the more I dug into monitoring container performance I quickly realized, Prometheus has established itself as the leading tool in this space and Docker also provides support for Prometheus – more on that later. So let’s start with an introduction to Prometheus and lay some foundations for a monitoring platform.
What is Prometheus?
Prometheus is an open-source application for monitoring systems and generating alerts. It can monitor almost anything, from servers to applications, databases, or even a single process. Prometheus monitors your defined targets by scraping metric data in a simple text format that is exposed by the target. Prometheus stores this metric data in a multi-dimensional data model by metric name and key/value in its timeseries database which can then be queried and retrieved using its own query language PromQL, in a nutshell.
Let’s take a quick look at the the main components and architecture that comprise of the Prometheus platform.
Occasionally you may need to connect to the Sitecore SQL instance and inspect the databases when running in docker. This is relatively straightforward.
Using SQL Manager
1. Identify the IP address of your SQL Instance
PS> docker inspect container [options] <container id/name>
NOTE: IP address changes every time you run docker-compose up.
If you are not sure of the name of your container name or id you can use the following command to get list of running containers
PS> docker container ls Continue reading
Over the course of several months I have had the opportunity to introduce the use of docker within development teams as an alternative approach for developing with Sitecore. Developing with Sitecore on Docker requires a bit of a mind shift from your normal way of working with Sitecore. But if offers many benefits like the ability to stand up a fully scaled instance of Sitecore in seconds rather than hours. This blog provides a introduction to docker and getting started developing with Sitecore on Docker.
What is Docker
Docker is a platform that enables you to develop, ship, and run applications as containers. The Docker Daemon process (or engine) runs on your host OS which manages images and containers.
The Command Line Interface (CLI) communicates with the docker daemon via rest API.
Containers vs VMs
Containers are an abstraction at the app layer that packages code and dependencies together. Multiple containers can run on the same machine and share the OS kernel with other containers, each running as isolated processes.
- take up less space.
- more portable and efficient.
- require fewer VMs and Operating systems.
- reduce cost as fewer licenses are required.
- start in seconds.
- are ephemeral – treated like cattle in your DevOps service model.
VMs are an abstraction of physical hardware turning one server into many servers. The hypervisor allows multiple VMs to run on a single machine.
- includes a full copy of an operating system, the application, necessary binaries and libraries – are much larger in size.
- VMs can also be slow to boot.
- start in minutes
- tend to hang around longer – treated more like pets in your DevOps service model.
By combining Containers and VMs in your infrastructure provide a great deal of flexibility in deploying and managing your application.
Sitecore Docker Repo
The Sitecore Docker Repo contains docker files for a plethora of Sitecore versions and their variants including: JSS, SXA, SPE. Also necessary scripts, tools and supporting documentation to help you build Sitecore Docker images and ultimately run a containerized instance of Sitecore.
Lets backup for those of you that may not be familiar with some of these terms:
- Dockerfile – is a text document that contains all the commands you would normally execute manually in order to build a Docker image.
Docker can build images automatically by reading the instructions from a Dockerfile.
- Docker Images – are the basis of containers. An Image is an ordered collection of root filesystem changes and the corresponding execution parameters for use within a container runtime. An image typically contains a union of layered filesystems stacked on top of each other. An image does not have state and it never changes.
- Docker Container– is a runtime instance of a docker image.
Thanks to the hardwork and dedication to the individuals in our community that contribute to the Sitecore Docker repo. Which is continually evolving.
The ability to monitor your Sitecore instances is essential. Knowing your application is available and performing in production as expected is critical. To be proactive and respond to changes in performance as opposed to reactive after an incident has occurred, you need a continuous overview of the state of the application and the underlying infrastructure. This involves gathering metrics like CPU, memory usage, and storage consumption as well as any application-related metrics. However, when monitoring a containerized Sitecore instance we cannot apply our usual methods and tools to provide us with all the data we need. In this post, I will show you some of the native tools to help you monitor Sitecore containers.
The docker stats command display a live stream (updated every second) of running containers resource usage statistics docker stats:
- CPU % – the percentage of the host’s CPU the container is using.
- PRIV WORKING SET – refers to the total physical memory (RAM) used by the process.
- NET I/O – the amount of data the container has sent and received over its network interface.
- BLOCK I/O – the amount of data the container has read to and written from block devices on the host.
In this post, I will show you some useful commands and tips for managing your Sitecore containers, images and other docker resources that get created when standing up your containers. The Docker documentation is awesome but it is fairly extensive so I’ll cover some useful commands you should be familiar with.
PS> docker container ls – lists running containers by default, you need to use -a flag to list all containers not just running containers. You can use -f flag to filter containers.
PS> docker container ls -f “name=93x*”
If you want to see the most recently created use -l flag.
If you have built your Sitecore container images and they reside locally and you want to share them with your team the recommended approach is a private registry and there are a few services available. However, Azure Container Registry (ACR) allows you to store docker images in repositories and can take advantage of the azure pipelines to automatically rebuild these images when they need to be updated. In this post, I will show you how to push your local images to a private ACR. This also works if you need to move your images from one private registry to another.
If you are running Sitecore in a container then you’ve most likely switched Docker desktop to Windows container mode. But what if you want to run a Linux container simultaneously? For example, you might want to fire up, JMeter and Grafana on Linux containers. It turns out this is possible in your local development environment and is fairly straightforward.
Don’t worry this is not another post about running Sitecore in a container! No this is a post about getting the Sitecore HabitatHome demo solution up and running quickly and I mean quickly without too much effort. I just happen to use docker in the process. HabitatHome is a solution built using SXA on Sitecore XP following Helix principles. It is extremely useful if you need to showcase SXA capabilities to an existing or a potential new customer.
This is where my good friend Andy Uzick found himself a few weeks ago but had already started down the path of standing up the SXA HabitatHome demo on a temporary Azure PAAS instance not using docker. I thought with docker surely this would be much easier.
Okay, so we all know the difference between Renderings and Final Renderings right? Final renderings were introduced in Sitecore 8 to make it possible to have different layouts for the various language and versions of an Item. Awesome!!
- __Renderings – a shared field where you specify the common layout for all languages and versions of the item.
- __Final Renderings – a versioned field where you specify individual layouts for languages and versions of the item.
I ran into an issue where I needed to modify the __Final Renderings for specific templates. A parameter of a component for a specific language in use on a site, needed to be updated. Continue reading