k8s_basic_deployments [My wiki]

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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:


{{:deploymentoverview.jpg?500|}}


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:

<Code: bash|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
</Code>


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:

<Code: bash|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

</Code>


Again, we can check if our app is working:

{{:deploymenttest.jpg?400|}}


====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.

<Code: bash|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.
</Code>

=====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====
<Code: C#|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));
            }
        }
    }
}
</Code>

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===
<Code: bash|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
</Code>

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:

<Code: bash| 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
</Code>

Once we have the file, you can start the process as so:

<Code: bash|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
</Code>


You can see the progress of the Rolling Update as follows:
<Code: bash|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...
</Code>

We can also check the version which is currently being used:

<Code: bash|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

</Code>

=====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:

<Code: bash| Check Change History>
ubuntu@k8s-master:~$ kubectl rollout history deploy hello-deploy
deployment.apps/hello-deploy
REVISION  CHANGE-CAUSE
1         <none>
2         <none>
</Code>

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:

<Code: bash| Rollback>
ubuntu@k8s-master:~$ kubectl rollout undo deployment hello-deploy --to-revision=1
deployment.apps/hello-deploy rolled back
ubuntu@k8s-master:~$
</Code>

Of course we can monitor it with the same command as before:

<Code: bash| 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
</Code>

====Rollupdate with Record====
Let's again apply the RollUpdate WITH the record this time:

<Code: bash|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
</Code>

Now, we can see that, the record is there and we can see the history of changes.