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@k8s-master:/home/vagrant/HttpServerDemo# docker build -t httpserverdemo .
Sending build context to Docker daemon 6.144kB
Step 1/11 : FROM mcr.microsoft.com/dotnet/core/sdk:3.1 AS build-env
---> 4aa6a74611ff
Step 2/11 : WORKDIR /app
---> Using cache
---> e6fb8470c359
Step 3/11 : COPY *.csproj ./
---> Using cache
---> c6e7e3257ccd
Step 4/11 : RUN dotnet restore
---> Using cache
---> 073b0e6dcfac
Step 5/11 : COPY . ./
---> dbb416239305
Step 6/11 : RUN dotnet publish -c Release -o out
---> Running in cdccacf739ec
Microsoft (R) Build Engine version 16.5.0+d4cbfca49 for .NET Core
Copyright (C) Microsoft Corporation. All rights reserved.
Restore completed in 38.37 ms for /app/HttpServerDemo.csproj.
HttpServerDemo -> /app/bin/Release/netcoreapp3.1/HttpServerDemo.dll
HttpServerDemo -> /app/out/
Removing intermediate container cdccacf739ec
---> 29d5a30972d4
Step 7/11 : FROM mcr.microsoft.com/dotnet/core/sdk:3.1
---> 4aa6a74611ff
Step 8/11 : WORKDIR /app
---> Using cache
---> e6fb8470c359
Step 9/11 : COPY --from=build-env /app/out .
---> ff034e158a2e
Step 10/11 : RUN find -type d -name bin -prune -exec rm -rf {} \; && find -type d -name obj -prune -exec rm -rf {} \;
---> Running in e217c60056a6
Removing intermediate container e217c60056a6
---> f3755f21e57e
Step 11/11 : ENTRYPOINT ["dotnet", "HttpServerDemo.dll"]
---> Running in e49283dde769
Removing intermediate container e49283dde769
---> 9f2f48860257
Successfully built 9f2f48860257
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
Once we have the file, you can start the process as so:
Rolling Update Status
ubuntu@k8s-master:~$ kubectl apply -f deploy.yml Warning: kubectl apply should be used on resource created by either kubectl create --save-config or kubectl apply deployment.apps/hello-deploy configured
You can see the progress of the Rolling Update as follows:
Rolling Update Status
ubuntu@k8s-master:~$ kubectl rollout status deploy hello-deploy Waiting for deployment "hello-deploy" rollout to finish: 2 out of 10 new replicas have been updated... ^Cubuntu@k8s-master:~$ kubectl get pods NAME READY STATUS RESTARTS AGE hello-deploy-6cd458494-6mvt7 1/1 Running 0 80s hello-deploy-6cd458494-9bl7c 1/1 Running 0 80s hello-deploy-6cd458494-fvwvz 1/1 Running 0 80s hello-deploy-6cd458494-grp2w 1/1 Running 0 80s hello-deploy-6cd458494-ldsxq 1/1 Running 0 80s hello-deploy-6cd458494-lpgdj 1/1 Running 0 80s hello-deploy-6cd458494-mjsmh 1/1 Running 0 80s hello-deploy-6cd458494-rd58j 1/1 Running 0 80s hello-deploy-6cd458494-rrkhq 1/1 Running 0 80s hello-deploy-7f44bd8b96-k92sr 0/1 ContainerCreating 0 23s hello-deploy-7f44bd8b96-lqmdx 0/1 ContainerCreating 0 23s ubuntu@k8s-master:~$ kubectl rollout status deploy hello-deploy Waiting for deployment "hello-deploy" rollout to finish: 4 out of 10 new replicas have been updated... Waiting for deployment "hello-deploy" rollout to finish: 4 out of 10 new replicas have been updated... Waiting for deployment "hello-deploy" rollout to finish: 6 out of 10 new replicas have been updated... Waiting for deployment "hello-deploy" rollout to finish: 6 out of 10 new replicas have been updated... Waiting for deployment "hello-deploy" rollout to finish: 6 out of 10 new replicas have been updated... Waiting for deployment "hello-deploy" rollout to finish: 6 out of 10 new replicas have been updated... Waiting for deployment "hello-deploy" rollout to finish: 6 out of 10 new replicas have been updated... Waiting for deployment "hello-deploy" rollout to finish: 8 out of 10 new replicas have been updated... Waiting for deployment "hello-deploy" rollout to finish: 8 out of 10 new replicas have been updated... Waiting for deployment "hello-deploy" rollout to finish: 8 out of 10 new replicas have been updated... Waiting for deployment "hello-deploy" rollout to finish: 8 out of 10 new replicas have been updated... Waiting for deployment "hello-deploy" rollout to finish: 8 out of 10 new replicas have been updated... Waiting for deployment "hello-deploy" rollout to finish: 1 old replicas are pending termination... Waiting for deployment "hello-deploy" rollout to finish: 1 old replicas are pending termination... Waiting for deployment "hello-deploy" rollout to finish: 1 old replicas are pending termination... Waiting for deployment "hello-deploy" rollout to finish: 1 old replicas are pending termination...
We can also check the version which is currently being used:
Rolling Update Status
ubuntu@k8s-master:~$ kubectl get deploy hello-deploy
NAME READY UP-TO-DATE AVAILABLE AGE
hello-deploy 10/10 10 10 5m7s
ubuntu@k8s-master:~$ kubectl describe deploy hello-deploy
Name: hello-deploy
Namespace: default
CreationTimestamp: Sun, 03 May 2020 11:28:33 +0000
Labels: <none>
Annotations: deployment.kubernetes.io/revision: 2
Selector: app=hello-date
Replicas: 10 desired | 10 updated | 10 total | 10 available | 0 unavailable
StrategyType: RollingUpdate
MinReadySeconds: 10
RollingUpdateStrategy: 1 max unavailable, 1 max surge
Pod Template:
Labels: app=hello-date
Containers:
hello-pod:
Image: andonovj/httpserverdemo:edge <- We are using the "edge" version, which we have just compiled.
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-7f44bd8b96 (10/10 replicas created)
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal ScalingReplicaSet 5m11s deployment-controller Scaled up replica set hello-deploy-6cd458494 to 10
Normal ScalingReplicaSet 4m14s deployment-controller Scaled up replica set hello-deploy-7f44bd8b96 to 1
Normal ScalingReplicaSet 4m14s deployment-controller Scaled down replica set hello-deploy-6cd458494 to 9
Normal ScalingReplicaSet 4m14s deployment-controller Scaled up replica set hello-deploy-7f44bd8b96 to 2
Normal ScalingReplicaSet 2m18s deployment-controller Scaled down replica set hello-deploy-6cd458494 to 7
Normal ScalingReplicaSet 2m18s deployment-controller Scaled up replica set hello-deploy-7f44bd8b96 to 4
Normal ScalingReplicaSet 2m3s deployment-controller Scaled down replica set hello-deploy-6cd458494 to 5
Normal ScalingReplicaSet 2m3s deployment-controller Scaled up replica set hello-deploy-7f44bd8b96 to 6
Normal ScalingReplicaSet 108s deployment-controller Scaled down replica set hello-deploy-6cd458494 to 3
Normal ScalingReplicaSet 82s (x4 over 108s) deployment-controller (combined from similar events): Scaled down replica set hello-deploy-6cd458494 to 0
Rolling Back
Now, before we continue, let's speak a little bit about Change History. We can check the history of all changes as follows:
Check Change History
ubuntu@k8s-master:~$ kubectl rollout history deploy hello-deploy deployment.apps/hello-deploy REVISION CHANGE-CAUSE 1 <none> 2 <none>
The reason why you don't see anything in the “change-cause” is because we didn't use “-record” when we applied the change. But let's reverse our changes and apply them again. We can reverse our changes using the following command:
Rollback
ubuntu@k8s-master:~$ kubectl rollout undo deployment hello-deploy --to-revision=1 deployment.apps/hello-deploy rolled back ubuntu@k8s-master:~$
Of course we can monitor it with the same command as before:
Rollback
ubuntu@k8s-master:~$ kubectl rollout status deploy hello-deploy
Waiting for deployment "hello-deploy" rollout to finish: 4 out of 10 new replicas have been updated...
Waiting for deployment "hello-deploy" rollout to finish: 4 out of 10 new replicas have been updated...
Waiting for deployment "hello-deploy" rollout to finish: 6 out of 10 new replicas have been updated...
Waiting for deployment "hello-deploy" rollout to finish: 6 out of 10 new replicas have been updated...
Waiting for deployment "hello-deploy" rollout to finish: 6 out of 10 new replicas have been updated...
Waiting for deployment "hello-deploy" rollout to finish: 6 out of 10 new replicas have been updated...
Waiting for deployment "hello-deploy" rollout to finish: 6 out of 10 new replicas have been updated...
Waiting for deployment "hello-deploy" rollout to finish: 8 out of 10 new replicas have been updated...
Waiting for deployment "hello-deploy" rollout to finish: 8 out of 10 new replicas have been updated...
Waiting for deployment "hello-deploy" rollout to finish: 8 out of 10 new replicas have been updated...
Waiting for deployment "hello-deploy" rollout to finish: 8 out of 10 new replicas have been updated...
Waiting for deployment "hello-deploy" rollout to finish: 8 out of 10 new replicas have been updated...
Waiting for deployment "hello-deploy" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "hello-deploy" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "hello-deploy" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "hello-deploy" rollout to finish: 1 old replicas are pending termination...
deployment "hello-deploy" successfully rolled out
ubuntu@k8s-master:~$ kubectl describe deploy
Name: hello-deploy
Namespace: default
CreationTimestamp: Sun, 03 May 2020 11:28:33 +0000
Labels: <none>
Annotations: deployment.kubernetes.io/revision: 3
Selector: app=hello-date
Replicas: 10 desired | 10 updated | 10 total | 10 available | 0 unavailable
StrategyType: RollingUpdate
MinReadySeconds: 10
RollingUpdateStrategy: 1 max unavailable, 1 max surge
Pod Template:
Labels: app=hello-date
Containers:
hello-pod:
Image: andonovj/httpserverdemo:latest <- We are back to the old deployment.
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 45m deployment-controller Scaled up replica set hello-deploy-6cd458494 to 10
Normal ScalingReplicaSet 44m deployment-controller Scaled up replica set hello-deploy-7f44bd8b96 to 1
Normal ScalingReplicaSet 44m deployment-controller Scaled down replica set hello-deploy-6cd458494 to 9
Rollupdate with Record
Let's again apply the RollUpdate WITH the record this time:
Rollupdate with Record
ubuntu@k8s-master:~$ kubectl apply -f deploy.yml --record deployment.apps/hello-deploy configured ubuntu@k8s-master:~$ ubuntu@k8s-master:~$ kubectl rollout history deploy hello-deploy deployment.apps/hello-deploy REVISION CHANGE-CAUSE 3 <none> 4 kubectl apply --filename=deploy.yml --record=true
Now, we can see that, the record is there and we can see the history of changes.