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This article mainly explains "how to build a project with .NET Core+Kubernetes". The content in the article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn how to build a project with .NET Core+Kubernetes.

In Kubernetes, controllers such as Deployment, Replicaset and Daemonset of Pod resources are often used to manage stateless applications. The corresponding IP, name, start and stop order of the Pod they manage are random, and there is no relationship between Pod. In fact, when deploying an application cluster, instances may need to be associated with each other (startup sequence, role), such as MySQL and MongoDB, so StatefulSet is a type of resource introduced to run stateful services. StatefulSet maintains a unique and fixed identifier for each Pod, creates a dedicated storage volume for it if necessary, and retains the original identifier and storage volume when the Pod is rebuilt.

A complete StatefulSet usually consists of three parts: StatefulSet, VolumeClaimTemplate, and Headless Service.

StatefulSet is used for the definition and control of Pod resources. In StatefulSet mode, Pod has its own fixed naming rules (StatfulSet name + index where Pod was created). Assuming that the StatefulSet name set is k8sdemothesis replicas is 3, the corresponding Pod names will be k8sdemo-0, k8sdemo-1 and k8sdemo-0, respectively. At the same time, the Pod replica can be scaled up and down by sequence number.

VolumeClaimTemplate is used to define the PVC declaration of storage required by Pod, and PVC binds with PV to provide proprietary fixed storage volumes.

Headless Service (clusterIP: None) is used to generate resolvable DNS domain name records for Pod. Based on the ordered rules of Pod names, Pod domain names will not change (Pod name .serviceName), which also ensures the stability of Pod network identity.

Let's continue to take the beckjin/k8sdemo:1.2.0 image built by the .NET Core project as an example, adding the ability of the interface to access logging. The API access log is recorded by integrating log4net, and the log is output to the / Data/ directory, and each Pod has its own log file (this is only a hypothetical scenario, so don't take it seriously. In fact, log recording generally uses a unified log collection tool).

Define resources

K8sdemo-statefulset.yaml:

ApiVersion: apps/v1

Kind: StatefulSet

Metadata:

Name: k8sdemo

Spec:

ServiceName: "k8sdemo-service" # needs to be consistent with the created service name

Replicas: 3

Selector:

MatchLabels:

Name: k8sdemo

Template:

Metadata:

Labels:

Name: k8sdemo

Spec:

Containers:

-name: k8sdemo

Image: beckjin/k8sdemo:1.2.0

ImagePullPolicy: IfNotPresent

VolumeMounts:

-name: data

MountPath: / app/Data # Mount the Data directory in the container

VolumeClaimTemplates: # define template and automatically create PVC

-metadata:

Name: data

Spec:

AccessModes:

-ReadOnlyMany

Resources:

Requests:

Storage: 100Mi

StorageClassName: "k8sdemo-sc" # will automatically bind to the PV that matches the storageClassName in the cluster

K8sdemo-service.yaml:

ApiVersion: v1

Kind: Service

Metadata:

Name: k8sdemo-service

Spec:

ClusterIP: None

Ports:

-port: 80

TargetPort: 80

Selector:

Name: k8sdemo

The serviceName field needs to be set in StatefulSet mode to tell the StatefulSet controller which service to use to parse the Pod it manages. At the same time, the PVC is defined through the volumeClaimTemplates field, and the StatefulSet controller automatically creates the name of the PVC,PVC corresponding to the Pod as (volumeClaimTemplateName)-(podName), and then the PVC is automatically bound to the PV that meets the requirements. If the PV does not support automatic creation, it can be done manually. In addition, when Pod is deleted, PVC and PV will still be retained, and the corresponding PVC and PV will be re-associated when Pod is rebuilt.

Here, we also use the NFS to create PV to implement storage, and create 3 (data-k8sdemo-pv- [1 / 3]) PV that meet the definition requirements, as follows:

ApiVersion: v1

Kind: PersistentVolume

Metadata:

Name: data-k8sdemo-pv-1

Spec:

Nfs:

Server: 192.168.124.21

Path: / statefulset/data1

AccessModes:

-ReadOnlyMany

Capacity:

Storage: 100Mi

StorageClassName: k8sdemo-sc

Deployment and testing

Create PV and StatefulSet:

Kubectl apply-f k8sdemo-statefulset-pv1.yaml

Kubectl apply-f k8sdemo-statefulset-pv2.yaml

Kubectl apply-f k8sdemo-statefulset-pv3.yaml

Kubectl apply-f k8sdemo-statefulset.yaml

Note: the PV naming order does not represent the binding order of the PVC, and there is no relationship between the two, so there is no need to question the numerical number correspondence of the figure above.

Create a Service:

Kubectl apply-f k8sdemo-service.yaml

Because Service defines Headless mode, you need to enter the Pod for API access testing. For example, kubectl exec-it k8sdemo-0 bash enters the Pod of k8sdemo-0 and accesses it through the domain name Pod. ServiceName, as follows:

Curl k8sdemo-0.k8sdemo-service/weatherforecast

Curl k8sdemo-1.k8sdemo-service/weatherforecast

Curl k8sdemo-2.k8sdemo-service/weatherforecast

View the API access log in the NFS mount directory. The following is the log in Pod k8sdemo-1:

2020-09-20 06 k8sdemo-1 01 http://k8sdemo-1.k8sdemo-service/weatherforecast 17451 [17] INFO [k8sdemo-1]-Request starting HTTP/1.1 GET

2020-09-20 06 INFO [17] INFO [k8sdemo-1]-Executing endpoint 'T.K8SDemo.Controllers.WeatherForecastController.Get (T.K8SDemo)'

2020-09-20 06 Route matched with 01 INFO [k8sdemo-1]-Route matched with {action = "Get", controller = "WeatherForecast"}. Executing controller action with signature system. Collection. Generic.IEnumerable`1 [T.K8SDemo.WeatherForecast] Get () on controller T.K8SDemo.Controllers.WeatherForecastController (T.K8SDemo).

2020-09-20 06 INFO [k8sdemo-1]-Executing ObjectResult, writing value of type 'T.K8SDemo.WeatherForecast []'.

2020-09-20 06 Executed action T.K8SDemo.Controllers.WeatherForecastController.Get 01 Executed action T.K8SDemo.Controllers.WeatherForecastController.Get 17460 [17] INFO [k8sdemo-1]-Executed action T.K8SDemo.Controllers.WeatherForecastController.Get (T.K8SDemo) in 2.3627ms

2020-09-20 06 Executed endpoint 01V 17460 [17] INFO [k8sdemo-1]-Executed endpoint 'T.K8SDemo.Controllers.WeatherForecastController.Get (T.K8SDemo)'

2020-09-20 06 Request finished in 9.9194ms 01 application/json; charset=utf-8 17461 [17] INFO [k8sdemo-1]-200 application/json; charset=utf-8

Execute kubectl delete pod k8sdemo-1 to delete Pod k8sdemo-1, wait for a while, k8sdemo-1 will automatically restore, and then revisit curl k8sdemo-1.k8sdemo-service/weatherforecast, and the log will still be appended to the original file, which means that the original state has been retained.

2020-09-20 06 k8sdemo-1 01 http://k8sdemo-1.k8sdemo-service/weatherforecast 17451 [17] INFO [k8sdemo-1]-Request starting HTTP/1.1 GET

2020-09-20 06 INFO [17] INFO [k8sdemo-1]-Executing endpoint 'T.K8SDemo.Controllers.WeatherForecastController.Get (T.K8SDemo)'

2020-09-20 06 Route matched with 01 INFO [k8sdemo-1]-Route matched with {action = "Get", controller = "WeatherForecast"}. Executing controller action with signature system. Collection. Generic.IEnumerable`1 [T.K8SDemo.WeatherForecast] Get () on controller T.K8SDemo.Controllers.WeatherForecastController (T.K8SDemo).

2020-09-20 06 INFO [k8sdemo-1]-Executing ObjectResult, writing value of type 'T.K8SDemo.WeatherForecast []'.

2020-09-20 06 Executed action T.K8SDemo.Controllers.WeatherForecastController.Get 01 Executed action T.K8SDemo.Controllers.WeatherForecastController.Get 17460 [17] INFO [k8sdemo-1]-Executed action T.K8SDemo.Controllers.WeatherForecastController.Get (T.K8SDemo) in 2.3627ms

2020-09-20 06 Executed endpoint 01V 17460 [17] INFO [k8sdemo-1]-Executed endpoint 'T.K8SDemo.Controllers.WeatherForecastController.Get (T.K8SDemo)'

2020-09-20 06 Request finished in 9.9194ms 01 application/json; charset=utf-8 17461 [17] INFO [k8sdemo-1]-200 application/json; charset=utf-8

2020-09-20 06 k8sdemo-1 17 Request starting HTTP/1.1 GET 06467 [12] INFO [k8sdemo-1]-Request starting HTTP/1.1 GET

2020-09-20 06 INFO [12] INFO [k8sdemo-1]-Executing endpoint 'T.K8SDemo.Controllers.WeatherForecastController.Get (T.K8SDemo)'

2020-09-20 06 INFO [12] INFO [k8sdemo-1]-Route matched with {action = "Get", controller = "WeatherForecast"}. Executing controller action with signature system. Collection. Generic.IEnumerable`1 [T.K8SDemo.WeatherForecast] Get () on controller T.K8SDemo.Controllers.WeatherForecastController (T.K8SDemo).

2020-09-20 06 INFO [12] INFO [k8sdemo-1]-Executing ObjectResult, writing value of type 'T.K8SDemo.WeatherForecast []'.

2020-09-20 06 INFO [12] INFO [k8sdemo-1]-Executed action T.K8SDemo.Controllers.WeatherForecastController.Get (T.K8SDemo) in 17.1904ms

2020-09-20 06 INFO [12] INFO [k8sdemo-1]-Executed endpoint 'T.K8SDemo.Controllers.WeatherForecastController.Get (T.K8SDemo)'

2020-09-20 06 Request finished in 84.3414ms 1715 06550 [12] INFO [k8sdemo-1]-200 application/json; charset=utf-8

In addition, the effect is the same when scaling a copy of Pod, which maintains the state that Pod has. Of course, the example in this paper is different from the cluster deployment of some components, such as MySQL, where data synchronization is performed among instances to achieve data consistency, and eventually each instance is associated with its own data storage volume.

Thank you for reading, the above is the content of "how to build a project with .NET Core+Kubernetes". After the study of this article, I believe you have a deeper understanding of how to build a project with .NET Core+Kubernetes, and the specific usage needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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