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Overview
Deployments, finally we have reached to the last major object in Kubernetes. Deployments take everything we have being doing so far and encapusaltes it. What I mean is the following:
Of course you can have more than 1 pod in replica set. Yes, it is replica set when under Deployment, not replication controller. But the purpose is the same.
So let's create our Deployment now:
Configuration
To create a deployment again we have two ways:
- Iterative - With kubectl create and so on
- Declarative - Using YML / JSON file, I will be using this one.
As I am bored with the iterative way, let's clean our env and create a deployment. I won't delete my service as I will use it later.
Create Deployment (Declarative)
First, let's create our YML file:
Create Deployment YML file
apiVersion: apps/v1
kind: Deployment
metadata:
name: hello-deploy
spec:
replicas: 10
selector:
matchLabels:
app: hello-date
template:
metadata:
labels:
app: hello-date
spec:
containers:
- name: hello-pod
image: andonovj/httpserverdemo:latest
ports:
- containerPort: 1234
Bare in mind that the deployment have been moved from extensions/v1beta1 → apps/v1 and forward :) Also a little syntax changes compared to the old one, but nothing serious.
Once we have the YAML file, we can continue as follows:
Create deployment
ubuntu@k8s-master:~$ kubectl create -f deploy.yml
deployment.apps/hello-deploy created
ubuntu@k8s-master:~$ kubectl get deploy
NAME READY UP-TO-DATE AVAILABLE AGE
hello-deploy 1/10 10 1 26s
ubuntu@k8s-master:~$ kubectl describe deploy
Name: hello-deploy
Namespace: default
CreationTimestamp: Sat, 02 May 2020 15:54:34 +0000
Labels: <none>
Annotations: deployment.kubernetes.io/revision: 1
Selector: app=hello-date
Replicas: 10 desired | 10 updated | 10 total | 10 available | 0 unavailable
StrategyType: RollingUpdate
MinReadySeconds: 0
RollingUpdateStrategy: 25% max unavailable, 25% max surge
Pod Template:
Labels: app=hello-date
Containers:
hello-pod:
Image: andonovj/httpserverdemo:latest
Port: 1234/TCP
Host Port: 0/TCP
Environment: <none>
Mounts: <none>
Volumes: <none>
Conditions:
Type Status Reason
---- ------ ------
Available True MinimumReplicasAvailable
Progressing True NewReplicaSetAvailable
OldReplicaSets: <none>
NewReplicaSet: hello-deploy-6cd458494 (10/10 replicas created)
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal ScalingReplicaSet 8m59s deployment-controller Scaled up replica set hello-deploy-6cd458494 to 10
Again, we can check if our app is working:
Replica Sets
As already mentioned, deployments operate with Replicat Sets, NOT replication Controllers. Eventhough that is a new objects, it inherits a lot of stuff from the replication controller. You can check the Replica sets, almost the same as the replication controller and notice that we don't have Replication Controllers anymore…after I have deleted them in the past of course.
Check Replica Sets
ubuntu@k8s-master:~$ kubectl get rs
NAME DESIRED CURRENT READY AGE
hello-deploy-6cd458494 10 10 10 11m
ubuntu@k8s-master:~$ kubectl get rc
No resources found in default namespace.
ubuntu@k8s-master:~$ kubectl describe rs
Name: hello-deploy-6cd458494
Namespace: default
Selector: app=hello-date,pod-template-hash=6cd458494
Labels: app=hello-date
pod-template-hash=6cd458494
Annotations: deployment.kubernetes.io/desired-replicas: 10
deployment.kubernetes.io/max-replicas: 13
deployment.kubernetes.io/revision: 1
Controlled By: Deployment/hello-deploy
Replicas: 10 current / 10 desired
Pods Status: 10 Running / 0 Waiting / 0 Succeeded / 0 Failed
Pod Template:
Labels: app=hello-date
pod-template-hash=6cd458494
Containers:
hello-pod:
Image: andonovj/httpserverdemo:latest
Port: 1234/TCP
Host Port: 0/TCP
Environment: <none>
Mounts: <none>
Volumes: <none>
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal SuccessfulCreate 16m replicaset-controller Created pod: hello-deploy-6cd458494-mjtw9
Normal SuccessfulCreate 16m replicaset-controller Created pod: hello-deploy-6cd458494-m9bgx
Normal SuccessfulCreate 16m replicaset-controller Created pod: hello-deploy-6cd458494-44jvs
Normal SuccessfulCreate 16m replicaset-controller Created pod: hello-deploy-6cd458494-6v8lt
Normal SuccessfulCreate 16m replicaset-controller Created pod: hello-deploy-6cd458494-zwh4l
Normal SuccessfulCreate 16m replicaset-controller Created pod: hello-deploy-6cd458494-jf594
Normal SuccessfulCreate 16m replicaset-controller Created pod: hello-deploy-6cd458494-vd7mt
Normal SuccessfulCreate 16m replicaset-controller Created pod: hello-deploy-6cd458494-nq2wx
Normal SuccessfulCreate 16m replicaset-controller Created pod: hello-deploy-6cd458494-f8j5f
Normal SuccessfulCreate 16m replicaset-controller (combined from similar events): Created pod: hello-deploy-6cd458494-dxqh7
ubuntu@k8s-master:~$ kubectl get rc
No resources found in default namespace. <- We don't have Replication Controllers anymore.
Rolling-Updates
Now, we have deployed application, which is totally scalable and redundancy is provided as Hell :) But what if want to fix couple bugs, or present new version.
What we do then ? Well, let's edit our application, let's add “v2” into our awesome app:
Edit Software
Edit Source
namespace HttpServerDemo
{
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Threading;
class Program
{
public async static Task Main(string[] args)
{
TcpListener tcpListener = new TcpListener(IPAddress.Any, 1234);
tcpListener.Start();
while (true)
{
TcpClient tcpClient = await tcpListener.AcceptTcpClientAsync();
await ProcessClientAsync(tcpClient);
}
}
public static async Task ProcessClientAsync(TcpClient tcpClient)
{
const string NewLine = "\r\n";
using (var networkStream = tcpClient.GetStream())
{
byte[] requestBytes = new byte[1000000]; //TODO USE Buffer
int bytesRead = await networkStream.ReadAsync(requestBytes, 0, requestBytes.Length);
string request = Encoding.UTF8.GetString(requestBytes, 0, bytesRead);
string responseText = @"<h1>Working... v2</h1>" + <- Updated this line with "v2" :)
$"<form> <h1> Time is: {System.DateTime.Now} </h1> </form>";
string response = "HTTP/1.1 200 OK" + NewLine
+ "Server: SoftuniServer/1.0 " + NewLine
+ "Content-Type: text/html" + NewLine
+ "Content-Length: " + responseText.Length + NewLine + NewLine
+ responseText;
byte[] responseBytes = Encoding.UTF8.GetBytes(response);
await networkStream.WriteAsync(responseBytes, 0, responseBytes.Length);
Console.WriteLine(request);
Console.WriteLine(new string('=', 60));
}
}
}
}
You see that “v2” after “Working”, yes, I just added it now. Let's rebuild via docker, upload it and edit our edition to v2 :) The Rebuild part you can see in the Docker section, but I will put the output here as well:
Dockerize, Tag & Push
Dockerize, Tag & Push
[root@postgresqlmaster httpserverdemo]# ls -lart total 16 -rw-r--r--. 1 root root 178 Jan 15 11:29 HttpServerDemo.csproj -rw-r--r--. 1 root root 405 Jan 24 07:20 Dockerfile -rw-r--r--. 1 root root 1904 May 2 12:19 Program.cs dr-xr-x---. 7 root root 4096 May 2 12:39 .. drwxr-xr-x. 2 root root 71 May 2 12:45 . [root@postgresqlmaster httpserverdemo]# docker build -t httpserverdemo . Sending build context to Docker daemon 5.632kB Step 1/10 : FROM mcr.microsoft.com/dotnet/core/sdk:3.1 AS build-env ---> 4aa6a74611ff Step 2/10 : WORKDIR /app ---> Using cache ---> b7f1f954c7e2 Step 3/10 : COPY *.csproj ./ ---> Using cache ---> eb10b9d797fa Step 4/10 : RUN dotnet restore ---> Using cache ---> 7db569180b05 Step 5/10 : COPY . ./ ---> c1d5d3f3ebb4 Removing intermediate container 56e2e79130b2 Step 6/10 : RUN dotnet publish -c Release -o out ---> Running in 8d0859d775dd Microsoft (R) Build Engine version 16.5.0+d4cbfca49 for .NET Core Copyright (C) Microsoft Corporation. All rights reserved. Restore completed in 49.81 ms for /app/HttpServerDemo.csproj. HttpServerDemo -> /app/bin/Release/netcoreapp3.1/HttpServerDemo.dll HttpServerDemo -> /app/out/ ---> b70ac7b2e6d8 Removing intermediate container 8d0859d775dd Step 7/10 : FROM mcr.microsoft.com/dotnet/core/aspnet:2.2 2.2: Pulling from dotnet/core/aspnet 804555ee0376: Already exists 970251047358: Pull complete f3d4c41a4fd1: Pull complete bd391c46585f: Pull complete Digest: sha256:08277d629af9d5324b63420a650cd96f86e73c4cfdcef6ea3c45912e7578956d Status: Downloaded newer image for mcr.microsoft.com/dotnet/core/aspnet:2.2 ---> e7e3b238011c Step 8/10 : WORKDIR /app ---> ceb374fc780a Removing intermediate container d77bfe0f6d8f Step 9/10 : COPY --from=build-env /app/out . ---> ee079c0d9469 Removing intermediate container 9bb39a98ec96 Step 10/10 : ENTRYPOINT dotnet HttpServerDemo.dll ---> Running in 99cf13dd6c77 ---> 452b7f6a095c Removing intermediate container 99cf13dd6c77 Successfully built 452b7f6a095c Successfully tagged httpserverdemo:latest [root@postgresqlmaster httpserverdemo]# [root@postgresqlmaster httpserverdemo]# docker image ls REPOSITORY TAG IMAGE ID CREATED SIZE httpserverdemo latest 452b7f6a095c About a minute ago 261MB [root@postgresqlmaster httpserverdemo]# docker tag 452b7f6a095c andonovj/httpserverdemo:v2 [root@postgresqlmaster httpserverdemo]# docker push andonovj/httpserverdemo:v2 The push refers to a repository [docker.io/andonovj/httpserverdemo] 9411dc505491: Pushed e595e200408f: Pushed 579a8f1d6a12: Pushed 15e45d99c926: Pushed 0cf75cb98eb2: Pushed 814c70fdae62: Pushed v2: digest: sha256:f83ed7e653ec409ba00e3710391608d124aac397b1abf6dab5c0482447137cdf size: 1579 [root@postgresqlmaster httpserverdemo]#
aaaaand….we are done :) We have edited our awesome software and uploaded it to docker hub.
Let's now update the containers in the pods :)
Perform the Update
For that purpose, we have to edit the YAML file with couple more values like:
- Strategy: RollingUpdate(default)
- maxUnavailable: 1 - Never have more than 1 unavailable
- maxSurge: 1 - Never have more than 1 additional. In our case, never have more than 11 pods
So, our YAML file should look as follows:
Updated YAML file
apiVersion: apps/v1
kind: Deployment
metadata:
name: hello-deploy
spec:
replicas: 10
minReadySeconds: 10
strategy:
type: RollingUpdate
rollingUpdate:
maxUnavailable: 1
maxSurge: 1
selector:
matchLabels:
app: hello-date
template:
metadata:
labels:
app: hello-date
spec:
containers:
- name: hello-pod
image: andonovj/httpserverdemo:v2
ports:
- containerPort: 1234