Do280 management application deployment --rc

DO280 Manage application deployment –RC

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REPLICATION CONTROLLERS

RC summary

RC Make sure pod A specified number of copies are always running . If pod Killed or explicitly deleted by the administrator , The replication controller will automatically deploy the appropriate pod. Similarly , If it runs pod The quantity exceeds the quantity required , It will be removed as needed pod, To match the specified replica count .

RC The definition of :

• Number of copies required
• Use to create replication pod Of pod Definition
• Used to identify subsequent administrative operations selector

selector It's a group. label,RC All that's managed pod Must match these tags .RC Instantiated pod The definition must contain the same set of tags .RC Use this selector To determine how much is running pod example , In order to make adjustments as needed .

Be careful ： Do not perform auto zoom , Because it doesn't track load or traffic .

Even though Kubernetes Usually directly manage RC, but OpenShift The recommended approach is to manage the creation or change of RC Of DC.

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from DC establish RC

stay OpenShift The most common way to create an application in is to use oc new-app Order or web Console . Applications created in this way use DeploymentConfig Resources are created at run time RC To create an application pod.DeploymentConfig The resource definition defines the pod The number of copies of , And the pod The template of .

** Be careful ：** Don't put DeploymentConfig or ReplicationController In resources template Attribute mistaking OpenShift Template resource type ,OpenShift Template resources are used to build applications based on common language runtimes and frameworks .

① Specify the... To run pod Number of copies ( Or copies ).

② The replication controller uses selectors to count running pod The number of , It's like a service using selectors to find the one to load balance pod equally .

③ Created by controller pods Templates .

④ Created by replication controller pods The label on must match the label on the selector **.**

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pod Copy number control

DeploymentConfig or ReplicationController The number of copies in the resource can be used oc scale Command dynamic change .

$ oc get dc
NAME REVISION DESIRED CURRENT TRIGGERED BY
myapp   1         3        3      config,image(scaling:latest)
$ oc scale --replicas=5 dc myapp

DeploymentConfig Resources pass change information to ReplicationController, The controller creates a new pod( copy ) Or delete existing pod To respond to changes .

Although it can be operated directly ReplicationController resources , But the recommended practice is operation DeploymentConfig resources . When a deployment is triggered , Direct pair ReplicationController Changes made by resources may be lost , for example , Using a container image A new version of is recreated pod.

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Automatic telescopic pod

OpenShift Can pass HorizontalPodAutoscaler The resource type depends on the application pod The current load on automatically adjusts the deployment configuration .

HorizontalPodAutoscaler (HPA) Use of resources OpenShift metrics Performance metrics collected by subsystems , That is, if there is no degree quantum system （ modular ）, More specifically Heapster Components , Automatic scaling is not possible .

establish HorizontalPodAutoscaler The recommended method for resources is to use oc autoscale command , for example :

$ oc autoscale dc/myapp --min 1 --max 10 --cpu-percent=80

This command creates a HorizontalPodAutoscaler resources , The resource changes myapp Number of copies on deployment configuration , In order to pod Of CPU Usage is controlled to the total number of requests CPU Used amount 80% following .

oc autoscale Command to use DC As a parameter ( In the previous example myapp) Create a HorizontalPodAutoscaler resources .

HorizontalPodAutoscaler The maximum and minimum values of resources are used to accommodate burst loads , And avoid OpenShift Cluster overload . If the load on the application changes too fast , It is recommended to keep some spare ones pod To handle sudden user requests . contrary , Too much pod All cluster capacity will be exhausted , And affect sharing the same OpenShift Other applications in the cluster .

To get the HorizontalPodAutoscaler Information about resources , You can use oc get and oc describe command . for example

$ oc get hpa/frontend
$ oc describe hpa/frontend

Be careful ：HorizontalPodAutoscaler Resources are only applicable to those that define resource requests for reference performance metrics pod.

oc new-app Most of the pod There are no resource requests defined . therefore , Use OpenShift autoscaler You may need to create custom YAML or JSON Resource file , Or add resource scope resources to the project .

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Textbook exercises

Environmental preparation

[[email protected] ~]$ lab install-prepare setup
[[email protected] ~]$ cd /home/student/do280-ansible
[[email protected] do280-ansible]$ ./install.sh

Tips ： If you already have a complete environment , Don't execute .

---

Create an

[[email protected] ~]$ oc login -u developer -p redhat https://master.lab.example.com
[[email protected] ~]$ oc new-project scaling
[[email protected] ~]$ oc new-app -o yaml -i php:7.0 \
http://registry.lab.example.com/scaling > ~/scaling.yml		# To be deployed yaml Export to local 
[[email protected] ~]$ vim ~/scaling.yml
……
  spec:
    replicas: 3
    selector:
      app: scaling
      deploymentconfig: scaling				# Number of modified copies 
……
[[email protected] ~]$ oc create -f ~/scaling.yml	# To modify the number of copies yaml Deploy the application 

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Monitor deployment

[[email protected] ~]$ watch -n 3 oc get builds
Every 3.0s: oc get builds                                                                     Wed Mar  3 21:31:11 2021

NAME        TYPE      FROM          STATUS     STARTED              DURATION
scaling-1   Source    [email protected]   Complete   About a minute ago   29s 
[[email protected] ~]$ oc get pods
NAME              READY     STATUS      RESTARTS   AGE
scaling-1-9dd8r   1/1       Running     0          1m
scaling-1-build   0/1       Completed   0          2m
scaling-1-r97zl   1/1       Running     0          1m
scaling-1-z4zdg   1/1       Running     0          1m

---

Exposure Services

[[email protected] ~]$ oc expose service scaling --hostname=scaling.apps.lab.example.com

---

web Check out the information

Browser access https://master.lab.example.com, Use developer Users and redhat Password login . choice scaling project .

---

Test load balancing

[[email protected] ~]$ oc get pod -o wide
NAME              READY     STATUS      RESTARTS   AGE       IP             NODE
scaling-1-9dd8r   1/1       Running     0          1h        10.128.0.189   node1.lab.example.com
scaling-1-build   0/1       Completed   0          1h        10.128.0.187   node1.lab.example.com
scaling-1-r97zl   1/1       Running     0          1h        10.129.0.253   node2.lab.example.com
scaling-1-z4zdg   1/1       Running     0          1h        10.128.0.188   node1.lab.example.com


[[email protected] ~]$ for i in {
    1..5};do curl -s http://scaling.apps.lab.example.com | grep IP;done
<br/> Server IP: 10.128.0.189 
 <br/> Server IP: 10.129.0.253 
 <br/> Server IP: 10.128.0.188 
 <br/> Server IP: 10.128.0.189 
 <br/> Server IP: 10.129.0.253

Browsers may not be able to strictly check the balance , because OpenShift route There is session affinity ( Also known as sticky conversation ). From the same one web All requests from the browser will go to the same pod.

---

Expansion application

[[email protected] ~]$ oc describe dc scaling | grep Replicas
Replicas:	3
	Replicas:	3 current / 3 desired
[[email protected] ~]$ oc scale --replicas=5 dc scaling

[[email protected] ~]$ oc get pod -o wide
NAME              READY     STATUS      RESTARTS   AGE       IP             NODE
scaling-1-9dd8r   1/1       Running     0          1h        10.128.0.189   node1.lab.example.com
scaling-1-build   0/1       Completed   0          1h        10.128.0.187   node1.lab.example.com
scaling-1-hmzk8   1/1       Running     0          33s       10.129.0.254   node2.lab.example.com
scaling-1-pf9bh   1/1       Running     0          33s       10.129.0.255   node2.lab.example.com
scaling-1-r97zl   1/1       Running     0          1h        10.129.0.253   node2.lab.example.com
scaling-1-z4zdg   1/1       Running     0          1h        10.128.0.188   node1.lab.example.com

---

Test load balancing

[[email protected] ~]$ for i in {
    1..5};do curl -s http://scaling.apps.lab.example.com | grep IP;done
 <br/> Server IP: 10.128.0.188 
 <br/> Server IP: 10.128.0.189 
 <br/> Server IP: 10.129.0.253 
 <br/> Server IP: 10.129.0.254 
 <br/> Server IP: 10.129.0.255

---

Clear the experiment

[[email protected] ~]$ oc delete project scaling
project "scaling" deleted

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summary

RHCA Certification requires experience 5 Study and examination of the door , It still takes a lot of time to study and prepare for the exam , Come on , Can GA 🤪.

That's all 【 Brother goldfish 】 Yes Chapter vii. DO280 Manage application deployment –RC Brief introduction and explanation of . I hope it can be helpful to the little friends who see this article .

Red hat Certification Column series ：
RHCSA special column ： entertain RHCSA authentication
RHCE special column ： entertain RHCE authentication
This article is included in RHCA special column ：RHCA memoir

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