Alex Xu Profile picture
Dec 2 9 tweets 3 min read
/1 What is k8s (Kubernetes)?

k8s is a container orchestration system. It is used for container deployment and management. Its design is greatly impacted by Google’s internal system Borg. Image
/2 A k8s cluster consists of a set of worker machines, called nodes, that run containerized applications. Every cluster has at least one worker node. [1]
/3 The worker node(s) host the Pods that are the components of the application workload. The control plane manages the worker nodes and the Pods in the cluster. [1]
/4 🔹 Control Plane Components

1. API Server
The API server talks to all the components in the k8s cluster. All the operations on pods are executed by talking to the API server.

2. Scheduler
The scheduler watches the workloads on pods and assigns loads on newly created pods. Image
/5 3. Controller Manager
The controller manager runs the controllers, including Node Controller, Job Controller, EndpointSlice Controller, and ServiceAccount Controller.

4. etcd
etcd is a key-value store used as Kubernetes' backing store for all cluster data. Image
/6 🔹 Nodes

1. Pods
A pod is a group of containers and is the smallest unit that k8s administers. Pods have a single IP address applied to every container within the pod.

2. Kubelet
An agent that runs on each node in the cluster. It ensures containers are running in a Pod. [1] Image
/7 3. Kube Proxy
kube-proxy is a network proxy that runs on each node in your cluster. It routes traffic coming into a node from the service. It forwards requests for work to the correct containers.
/8 👉 Over to you: Do you know why Kubernetes is called “k8s”?

Reference:
[1] kubernetes.io/docs/concepts/…
/9 I hope you've found this thread helpful.

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More from @alexxubyte

Nov 30
1/ What are the differences between monolithic and microservice architecture?

The diagram compares monolithic and microservice architecture in the ideal world.
2/ Suppose we have an eCommerce website that needs to handle the functions below:

🔹 User Management
🔹 Procurement Management
🔹 Order Management
🔹 Inventory Management
🔹 Payments
🔹 Logistics
3/ In a monolithic architecture, all the components are deployed in one single instance. The service calls are within the same process, and no RPCs. The data tables relating to each component are usually deployed in the same database.
Read 9 tweets
Nov 23
1/10 Session, cookie, JWT, token, SSO, and OAuth 2.0 - what are they? Image
2/10 These terms are all related to user identity management. When you log into a website, you declare who you are (identification). Your identity is verified (authentication), and you are granted the necessary permissions (authorization).
3/10 Many solutions have been proposed in the past, and the list keeps growing.
Read 10 tweets
Nov 22
/1 Last week, Ticketmaster halted public ticket sales of Taylor Swift’s tour due to extraordinarily high demands on ticketing systems. Image
/2 It’s an interesting problem, so we did some research on this topic. The diagram below shows the evolution of the online China Train ticket booking system.
/3 The China Train tickets booking system has 𝐬𝐢𝐦𝐢𝐥𝐚𝐫 𝐜𝐡𝐚𝐥𝐥𝐞𝐧𝐠𝐞𝐬 as the Ticketmaster system:

1️⃣ Very high concurrent visits during peak hours.
2️⃣ The QPS for checking remaining tickets and orders is very high
3️⃣ A lot of bots Image
Read 10 tweets
Nov 21
/1 Do we have 𝐚𝐧 𝐚𝐥𝐭𝐞𝐫𝐧𝐚𝐭𝐢𝐯𝐞 for Twitter services?

What is 𝐝𝐞𝐜𝐞𝐧𝐭𝐫𝐚𝐥𝐢𝐳𝐞𝐝 𝐬𝐨𝐜𝐢𝐚𝐥 𝐧𝐞𝐭𝐰𝐨𝐫𝐤 service?

The diagram below shows a comparison between Twitter and Mastodon. Image
/2 It is said that Trump's new social media platform Truth Social was using the Mastodon.

Mastodon runs 𝐬𝐞𝐥𝐟-𝐡𝐨𝐬𝐭𝐞𝐝 services. It is free and 𝐡𝐚𝐬 𝐧𝐨 𝐚𝐝𝐬. It's MAU increased from 500k in Oct to 1 million in Nov, after Elon Musk’s takeover of Twitter. Image
/3 Unlike Twitter, whose servers belong to the Twitter company, Mastodon’s servers do not belong to any company. Its network is composed of servers (instances) from different organizations.
Read 7 tweets
Nov 18
/1 One picture is worth more than a thousand words. In this post, we will take a look at what happens when Alice sends an 𝐄𝐦𝐚𝐢𝐥 to Bob. Image
/2 1. Alice logs in to her Outlook client, composes an email, and presses “send”. The email is sent to the Outlook mail server. The communication protocol between the Outlook client and mail server is SMTP. Image
/3 2. Outlook mail server queries the DNS (not shown in the diagram) to find the address of the recipient’s SMTP server. In this case, it is Gmail’s SMTP server. Next, it transfers the email to the Gmail mail server. The communication protocol between the mail servers is SMTP. Image
Read 12 tweets
Nov 16
Code First v.s. API First - A change of software development philosophy.

The diagram below shows the differences between code-first development and API-first development. Why do we want to consider API first design?

1 of 10
🔹Microservices increase system complexity

We have separate services to serve different functions of the system. While this kind of architecture facilitates decoupling and segregation of duty, we need to handle the various communications among services.

2 of 10
It is better to think through the system's complexity before writing the code and carefully defining the boundaries of the services.

3 of 10
Read 10 tweets

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