A self-sufficient system is a system capable of healing and adaptation. Healing means that the cluster will always be in the designed state. As an example, if a replica of a service goes down, the system needs to bring it back up again. Adaptation, on the other hand, is about modifications of the desired state so that the system can deal with changed conditions. A simple example would be increased traffic. When it happens, services need to be scaled up. When healing and adaptation are automated, we get self-healing and self-adaptation. Together, they both a self-sufficient system that can operate without human intervention.
How does a self-sufficient system look? What are its principal parts? Who are the actors?
The third installment in The DevOps Toolkit Series is public! Even though, while I'm writing this post, only 20% of The DevOps 2.2 Toolkit: Self-Healing Clusters is finished, I hope you'll pick it up and send me your feedback. I need your help in setting the direction of the book. I need you to help me shape it into something great. I need you to help me make this book a community effort.
Please get it from leanpub.com/the-devops-2-2-toolkit. I'm waiting for your feedback.
What follows is the preface to The DevOps 2.2 Toolkit: Self-Healing Clusters book.
Docker 1.13 introduced a set of features that allow us to centrally manage secrets and pass them only to services that need them. They provide a much-needed mechanism to provide information that should be hidden from anyone except designated services.
A secret (at least from Docker's point of view) is a blog of data. A typical use case would be a certificate, SSH private keys, passwords, and so on. Secrets should stay secret meaning that they should not be stored unencrypted or transmitted over a network.
I am continuously getting questions about blue-green releases inside a Docker Swarm cluster. Viktor, in your The DevOps 2.0 Toolkit book you told us to use blue-green deployment. How do we do it with services running inside a Swarm cluster? My answer is usually something along the following lines. With the old Swarm, blue-green releases were easier than rolling updates (neither were supported out of the box). Now we got rolling updates. Use them! The reaction to that is often that we still want blue-green releases.
This post is my brainstorming on this subject. I did not write it as a result of some deep thinking. There is no great wisdom in it. I just wrote what was passing through my mind while I was trying to answer another one of the emails containing blue-green deployment questions. What follows might not make much sense. Don't be harsh on me.
Bells are ringing! Docker v1.13 is out!
The most common question I receive during my Docker-related talks and workshops is usually related to Swarm and Compose.
Someone: How can I use Docker Compose with Docker Swarm?
Me: You can't! You can convert your Compose files into a Bundle that does not support all Swarm features. If you want to use Swarm to its fullest, be prepared for
docker service create commands that contain a never ending list of arguments.
I published The DevOps 2.1 Toolkit: Docker Swarm on LeanPub early. I think that only around 20% was written when it went public. That allowed you to get early access to the material, and me to get your feedback. The result is fantastic. Many send me their notes, reported bugs, proposed suggestions for improvements, recommended tools and processes that should be explored, and so on.
In the Forwarding Logs From All Containers Running Anywhere Inside A Docker Swarm Cluster article, we managed to add centralized logging to our cluster. Logs from any container running inside any of the nodes are shipped to a central location. They are stored in ElasticSearch and available through Kibana. However, the fact that we have easy access to all the logs does not mean that we have all the information we would need to debug a problem or prevent it from happening in the first place. We need to complement our logs with the rest of the information about the system. We need much more than what logs alone can provide.
In this article, we'll discuss a way to forward logs from containers created as Docker Swarm services inside our clusters. We'll use the ELK stack. They'll be forwarded from containers to LogStash and, from there, to ElasticSearch. Once in the database, they will be available through Kibana.
In this article, we'll discuss a way to create a Jenkins service inside a Docker Swarm cluster and some of the benefits such a service provides.