Demystifying
the Nuts & Bolts of
Kubernetes
Architecture
2
Who Am I?
• Principal Systems Development Engineer at DellEMC
• Worked with VMware & CGI
• Docker Captain | Docker Community Leader
• Collabnix Slack – 1800+ Members
• DockerLabs – 500+ tutorials
http://www.collabnix.com
Let’s start with an analogy..
A Cargo Ship…
Carries containers across the sea
A Cargo Ship…
Host Application as Containers ~ Worker Nodes
6
Overview
Worker Node-1
7
Control Ships..
Managing & Monitoring of the cargo ships
8
Control Ships..
Manage, Plan, Schedule, Monitor ~ Master
9
Overview
Worker Node-1
Master
Let’s talk about Master
Components..
11
Ship Cranes
Identifies the placement of containers
12
Ship Cranes
Identifies the right node to place a containers ~ Kube-Scheduler
13
Overview
Worker Node-1
Master
Scheduler
14
Cargo Ship Profiles
HA database ~ Which containers on which ships? When was it loaded?
15
Cargo Ship Profiles
HA database ~ Which containers on which ships? When was it loaded? ~ The ETCD Cluster
16
Overview
Worker Node-1
Master
Scheduler
ETCD
17
Offices in Dock
- Operation Team Office ~ Ship Handling, Control
- Cargo Team Office ~ verify if containers are damaged, ensure that new containers are rebuilt
- IT & Communication Office – Communication in between various ships
18
Controllers
- Node Controllers – Takes care of Nodes | Responsible for onboarding new nodes in a
cluster | Availability of Nodes
- Replicas Controller – Ensures that desired number of containers are running at all times
- Controller Manager - Manages all these controllers in place
19
Overview
Worker Node-1
Master
Scheduler
ETCD
Controller
Manager
20
How does each of these service communicate with
each other?
21
Kube API Server
API Server
- A primary management component of k8s
- Responsible for orchestrating all operations within a cluster
- Exposes K8s API ,used by external users to perform management operation in
the cluster and number of controller to monitor the state of the cluster
22
Overview
Worker Nodes
Master
Scheduler
ETCD
Controller
Manager
API Server
API
kubectl
UI
23
In nutshell…
$kubectl get componentstatus
[node1 install]$ kubectl get nodes -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-
RUNTIME
node1 Ready master 92s v1.14.2 192.168.0.18 <none> CentOS Linux 7 (Core) 4.4.0-141-generic docker://18.9.6
node2 Ready <none> 57s v1.14.2 192.168.0.17 <none> CentOS Linux 7 (Core) 4.4.0-141-generic docker://18.9.6
node3 NotReady <none> 39s v1.14.2 192.168.0.16 <none> CentOS Linux 7 (Core) 4.4.0-141-generic docker://18.9.6
node4 NotReady <none> 32s v1.14.2 192.168.0.15 <none> CentOS Linux 7 (Core) 4.4.0-141-generic docker://18.9.6
[node1 install]$ kubectl get componentstatus
NAME STATUS MESSAGE ERROR
scheduler Healthy ok
controller-manager Healthy ok
etcd-0 Healthy {"health":"true"}
Let’s talk about Worker
Components..
25
Overview
A Worker Node
Master
Scheduler
ETCD
Controller
Manager
API Server
API
kubectl
UI
26
Captain of the Ship
- Manages all sort of activity on the ship
- Let master ship knows they are interested to join
- Sending reports back to master about the status of the ship
- Sending reports about the status of the containers
27
Captain of the Ship ~ Kubelet
Agent which runs on each nodes of the container
28
Overview
Worker Node-1
Master
Scheduler
ETCD
Controller
Manager
API Server
Kubelet
API
kubectl
UI
29
Communication between Cargo Ships
How does two cargo ships communicate with each other?
30
Kube-proxy Service
How will web server running on one worker node reach out to DB server
on another worker node?
Communication between worker nodes
Kube-proxy
31
Overview
Worker Node-1
Master
Scheduler
ETCD
Controller
Manager
API Server
Kubelet
Kube-proxy
Internet
Let’s talk about Pods..
33
Overview
Worker Node-1
Master
Scheduler
ETCD
Controller
Manager
API Server
Kubelet
Kube-proxy
Internet
Pod
34
Overview
Worker Node-1
Master
Scheduler
ETCD
Controller
Manager
API Server
Kubelet
Kube-proxy
Internet
Pod
Container
35
Docker Containers
A popular Container Runtime
36
Overall Kubernetes Architecture
Worker Node
Master
Scheduler
ETCD
Controller
Manager
API Server
Kubelet
Kube-proxy
Internet
Pod
Container
API
kubectl
UI
37
Demo
• Setting up 5 Node Kubernetes Cluster on PWK