Skip to main content

Kubernetes: Node Time Like Show Time

The title was initially 'Bring Back the Node', but I didn't think people would get the reference. Applause if you did!




Making a deployment in the previous post made a POD for our application to be hosted in.

($POD_NAME variable)

Pods are an abstraction that represent 1 or more containers and shared resources for them, like Volumes, what the page describes as

‘Networking, as a unique cluster IP address’ (Sounds exciting, like a distant relative of subnetting or vlans)

 and instructions on  how to actually run the containers.





A Pod can hold the application and something that is closely coupled to it. The example given is a Node.js app and the data to be read by it.

Pods hold containers, and the containers share an IP address / Port space
Are co-located and scheduled, and
Run in a shared context on the same Node.

When we create a Deployment, that Deployment creates Pods with Containers inside of them.

The hierarchy reminds me a bit of Forests/Trees. Or Matryoshka dolls.

Pods run on Nodes, a virtual or physical worker machine in Kubernetes, and is managed by the Master.

Nodes = Multiple pods, Master schedules pods automatically across Nodes in the cluster.

Every Node runs at least a Kubelet and a container runtime, that pulls the container image from a registry, unpackets it, and runs it.

I’m just going to link to the image they provide. It looks like a cell.

So;

* Nodes hold pods and pods hold volumes and containerized apps.
* and there are some processes on the node.

Let’s troubleshoot with kubectl.

The syntax is kubectl [action]

- get [resource]; Lists resources
- describe; Show details about a resource
- logs; Print logs from a container
- exec; Execute a command on a podded container.
And those are what we’re going to be using in today’s tutorial!

Just putting in kubectl get with no specifics lists a lot of things.

Whoa nelly. 

adding pods gives us just the one.



But what’s in our pod? Describe it.


That’s not even all of the information!

Time to debug through a proxy in another terminal window.


We’re going to store this into the POD_NAME variable.

the curl request shows the output
{curl http://localhost:8001/api/vi/namespaces/default/pods/$POD_NAME/proxy}
The very long Pod name is in that variable, we don’t have to type it out, just $POD_NAME. Nice.

If there was more than one Pod, it wouldn't work.

What about our container logs? Let’s use
kubectl logs $POD_NAME


"Where are you running? WHERE are you running?"

Cool, now let’s execute a command.

The pod should be up and running, and we use the exec variable instead of get.



(env = enviroment variables, I think. I looked it up.)
(using SSL port 443)

Let’s start a bash in the Pod container with kubectl exec -ti $POD_NAME bash

Oh, we’ve moved to the root of our container! See the prompt over there?


 Now we can run the application with cat [where the source code is stored].
And check it again with a curl command. Close the container with an exit command.

Comments

Popular posts from this blog

Making KPI Dashboards with PowerBI

 While this is the free tier, I cannot share or collaborate with others, nor can I publish content to other people's workspaces, but they will not stop me from screenshooting and recording these self-taught adventures,so! I'm doing this because I idly searched "Mattel careers" and "Information Technology", and seeing a bulletpoint saying the following: Analytical and reporting skills such as creating dashboards and establishing KPIs such as experience with PowerBI, Cognos, Tableau, and Google Data Lake/AWS is preferred And thought "Well, I've used Tableau, and I've heard about PowerBI,  even if its in-demandness is questionable , so how similar is it? And can I write about it?"  First, PowerBI (PIB) does have a downloadable, local version, but apparently Windows-only. I could download the .exe but I couldn't run it / drag it to applications on my MacBook.  Not a problem, we'll use the online SaaS version, and a dataset found here, ...

Connecting IoT Devices to a Registration Server (Packet Tracer, Cisco)

 If you're seeing this post, I'm helping you, and you probably have LI presence: React and share this post to help me in return.   In Packet Tracer, a demo software made by Cisco Systems. It certainly has changed a lot since 2016. It's almost an Olympic feat to even get started with it now, but it does look snazzy. This is for the new CCNA, that integrates, among other things, IoT and Automation, which I've worked on here before. Instructions here . I don't know if this is an aspect of "Let's make sure people are paying attention and not simply following blindly", or an oversight - The instructions indicate a Meraki Server, when a regular one is the working option here. I have to enable the IoT service on this server. Also, we assign the server an IPv4 address from a DHCP pool instead of giving it a static one. For something that handles our IoT business, perhaps that's safer; Getting a new IPv4 address every week or so is a minimal step against an...

AWS Infrastructure Composer

 A very brief look. The text says; Drag and drop any CloudFormation resource on a visual canvas Connect and configure enhanced components to automatically build IaC for an application architecture Seamlessly transition between authoring workflows visually with Step Functions Workflow Studio and defining resources with Infrastructure Composer Integrate your browser with your project through “local sync” or use Composer in the AWS Toolkit for Visual Studio Code In 2019 there was a similar tool to build infrastructure that would be converted to code. Nice to know they bought it back. When you enter the Composer, it's a blank space with a background reminiscent to the screen for Cloud Formation. Infrastructure Objects are to the left in a drawer;  I've selected a bucket that I can rename. I went to connect a bucket to a Dynamo DB Table, and it's not available yet. It also lost a bucket somewhere in the ether of the GUI. Ah well. I couldn't find the EC2 instance in the...