Cloud-Native Learn-by-Doing Platforms (part 2) ✏️

I closely reviewed 10+ platforms providing a hands-on learning experience to study:

- Linux
- Containers
- Orchestration
- other Cloud-Native stuff

My findings (thread) 🔽

#kubernetes #docker #containers #linux #sre #devops
1. A Cloud Guru (acloudguru .com)

A really massive platform for individuals and businesses.

- 360+ courses and 1,600+ hands-on labs
- Clouds: AWS, GCP, etc.
- Tech: Kubernetes, Docker, Serverless

- Servers
- Temporary cloud accounts

2. Developer Sandbox for Red Hat OpenShift (developers.redhat .com/developer-sandbox)

A free platform with a private OpenShift playground:
7 GB RAM, 15GB storage 🔥

Almost no educational content, but combines well with kubebyexample .com.
3. Katacoda (katacoda .com)

Interactive learning and training platform for software engineers.

Katacoda is multipurpose. It provides:

- An extensive set of learning materials
- Environment to create your own hands-on labs (eg. envoyproxy. io/try)

Learning content is FREE!
4. KodeKloud (kodekloud .com)

One of my favorites ❤️

KodeKloud focuses on providing a truly immersive learning experience with the combination of video lectures and gamified hands-on labs.

Check out The Game of Pods, it's free!

20+ courses

5. Play with Docker (play-with-docker .com)

Try out Docker without installing it on the personal machine.

The resource also includes a set of interactive hands-on labs and quizzes from the beginner to the advanced level.
Check out the complete overview of Cloud-Native Learn-by-Doing platforms on my blog.…

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More from @iximiuz

30 Aug
iptables - a userspace program to configure IP packets filtration and modification rules.

It's a dated but still widely used tool:

- Linux firewall
- Container egress (SNAT) and port publishing (DNAT)
- Kubernetes service discovery
- Service Mesh transparent injection
- etc. 🔽 Image
iptables comes with its own terminology:

- tables
- chains
- rules
- targets
- policies

...that might be challenging to grasp. Here is how I approach it.

1. Come up with a logical model of packet processing inside the Linux kernel. Give meaningful names to stages. Image
2. Understand possible packet paths through the kernel.

Packet from a local process:

Packet to a local process:

Packet forwarded between interfaces:
Read 6 tweets
22 Aug
How to Expose Multiple Containers On the Same Port

First off, why you may need it:

- Load Balancing - more containers mean more capacity
- Redundancy - if one container dies, there won't be downtime
- Single Facade - run multiple apps behind one frontend

Interested? Read on!🔽
Docker doesn't support binding multiple containers to the same host port.

Instead, it suggests using an extra container with a reverse proxy like Nginx, HAProxy, or Traefik.

Here are two ways you can trick Docker and avoid adding the reverse proxy:

2. iptables
Multiple Containers On the Same Port w/o Proxy (I)

1) Use SO_REUSEPORT sockopt for your server sockets
2) Run containers with `--network host` and the same port

SO_REUSEPORT allows binding diff processes to the same port.
--network host puts all containers on one network stack.
Read 8 tweets
21 Aug
Containers are Virtual Machines (controversial thread)

Some mental gymnastics. Bear with me.

Person A comes to Containers with prior VM experience.
Dockerfiles start FROM debian/centos/etc.
docker run/exec feels like SSH-ing sessions into servers.

Containers are VMs!
A container starts in less than a second
A VM takes tens of seconds to start

A bare-metal server can run hundreds of containers
Only a few VMs can coexist on a server

How come?

Person A starts digging into the internals to understand the difference between containers and VMs.
Person A: Aha! Containers are just isolated and restricted Linux processes + OS-level virtualization!

Person A starts sharing the finding with friends and colleagues - seasoned backend devs. Everyone instantly grasps the idea.

Then a Person B comes by. W/o prior VM experience.
Read 7 tweets
15 Aug
Grasping Kubernetes Networking (Mega Thread)

- What is Kubernetes Service?
- When to use ClusterIP, NodePort, or LoadBalancer?
- How does multi-cluster service work?
- Why both Ingress and Ingress Controller?

The answers become clear when things are explained bottom-up! 🔽
1. Low-level Kubernetes Networking Guarantees

To make Pods mimicking traditional VMs, Kubernetes defines its networking model as follows:

- Every Pod gets its own IP address
- Pods talk to other Pods directly (no visible sNAT)
- Containers in a pod communicate via localhost
2. Kubernetes does nothing for low-level networking!

It delegates the implementation to Container Runtimes and networking plugins.

A typical example: cri-o (CR) connects pods on a node to a shared Linux bridge; flannel (plugin) puts nodes into an overlay network.
Read 13 tweets
10 Aug
How to become a server-side ninja (thread)

1. Try different programming paradigms

My personal recommendation

- PHP - simplest, traditional
- Python - more generic, traditional
- JavaScript - enter the async world!
- Go - learn goroutines
- Scala/Clojure - functional
2. Try different server-side frameworks

Don't try to learn all ins and outs. Instead, learn what's common for all frameworks.

- Request handling - processes, threads, coroutines
- Request routing - how to bind code to requests attrs
- Templating
- ORM integrations
3. Learn your platform

Linux basics - sockets, i/o, filesystem
Network basics - Ethernet, IP, TCP, HTTP
DNS - hostnames are only for humans
TLS, HTTPS - how X.509 certificates work

Learn SysAdmin craft - how to install packages, configure servers, troubleshoot perf issues.
Read 5 tweets
9 Aug
The idea of Kubernetes Operators is simple and attractive.

But as it usually happens, the devil is in the details. I've been working on an operator for the past few weeks, and the learning curve is quite steep, actually.

Here are some projects that may help 🔽
1. kubernetes-sigs/kubebuilder

GitHub says it's an "SDK for building Kubernetes APIs using CRDs."

But you can scaffold an operator project with it.
2. operator-framework/operator-sdk

Much like kubebuilder, this project allows you to scaffold an operator real quick.

The difference is that it comes with batteries included:

- support of Ansible and Helm operators
- simplifies releasing operators (OLM)
- e2e testing
- linting
Read 7 tweets

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