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https://github.com/jeffgbutler/csharp-payment-calculator


https://github.com/jeffgbutler/csharp-payment-calculator

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# C# Payment Calculator



.Net application that implements a loan payment calculator. The application includes a hit counter that can

either use an in-memory cache, or connect to Redis.



Use the following page to simulate traffic: https://jeffgbutler.github.io/payment-calculator-client/



## Steeltoe



This application uses the Steeltoe (https://steeltoe.io/) package to add these specific capabilities:



1. We use the Steeltoe Management extension (https://docs.steeltoe.io/api/v3/management/) to add URL endpoints

   useful for monitoring the application. These endpoints are also used by several Tanzu consoles to report application

   health and to enable other capabilities. 

2. We use the Steeltoe Redis connector (https://docs.steeltoe.io/api/v3/connectors/redis.html) to attach the application

   to a Redis database when running in production. The connector will use a Kubernetes service binding if one is

   available.



## Application Environments and Redis



When the application is run in the "Development" environment, then the application will use an in-memory cache

for a hit counter. This is used to demonstrate the dangers of doing such a thing - if multiple instances run then

the hit counters will not be in sync and the hit counter will not persist.



In other environments, the application will attempt to connect to a Redis instances for the hit counter. By default,

the application will attempt to connect to redis at "localhost:6379". We will show how to change that where appropriate.



Also note that the application will respect a service binding (https://servicebinding.io/) if one is available on a

Kubernetes cluster.



- [Build the Image](#build-an-image-with-cloud-native-buildpacks)

- [Run in Docker without Redis](#run-the-application-in-docker-without-redis)

- [Run in Docker with Redis](#run-the-application-in-docker-with-redis)

- [Run in Kubernetes](#run-the-application-in-kubernetes)

  - [Run in Kubernetes without Redis](#run-the-application-in-kubernetes-without-redis)

  - [Run in Kubernetes with Redis](#run-the-application-in-kubernetes-with-redis)



## Build an Image with Cloud Native Buildpacks



**Important:** .Net builds are not currently supported on Macs with Apple Silicon!



### Pre-requisites



Docker must be installed!



Install the pack CLI:



```shell

brew install buildpacks/tap/pack

```



### Build the Application



This will create/update an image named "csharp-payment-calculator" in your local Docker registry:



```shell

pack build csharp-payment-calculator --builder paketobuildpacks/builder-jammy-base

```



## Run the Application in Docker Without Redis



This is used for a quick test and does not connect to Redis:



```shell

docker run --detach --publish 8080:8080 --env ASPNETCORE_ENVIRONMENT=Development csharp-payment-calculator

```



Sample URLs:



- http://localhost:8080/swagger/index.html

- http://localhost:8080/actuator



## Run the Application in Docker With Redis



Create a Docker network:



```shell

docker network create payment-calculator-network

```



Deploy redis:



```shell

docker run --name redis --detach --network payment-calculator-network redis

```



Deploy the application. This command tells the application where to find Redis. By default, the Steeltoe connector

will look for Redis at "localhost:6379", so we'll need to change that.



(See this page for details about the properties that can be specified for the Redis

connector: https://docs.steeltoe.io/api/v3/connectors/redis.html)



```shell

docker run --detach --publish 8080:8080 --network payment-calculator-network \

  --env Redis__Client__Host=redis csharp-payment-calculator

```



Sample URLs:



- http://localhost:8080/swagger/index.html

- http://localhost:8080/actuator



## Run the Application in Kubernetes



Push app into an accessible registry. I'm using a private Harbor installation, change the following as applicable for

your environment:



```shell

docker login harbor.tanzuathome.net



docker tag csharp-payment-calculator:latest \

  harbor.tanzuathome.net/library/csharp-payment-calculator:latest



docker push harbor.tanzuathome.net/library/csharp-payment-calculator:latest

```



### Run the Application in Kubernetes Without Redis



Deploy app with in memory cache (you will need to change the image link for your registry):



```shell

kubectl apply -f Kubernetes/deployment-in-memory.yaml

```



If you have a loadBalancer service available, then:



```shell

kubectl apply -f Kubernetes/service.yaml

```



Else:



```shell

kubectl port-forward deployment/payment-calculator 28015:8080

```



Test URLs:



If you have a LoadBalancer, you can hit the following URLs:



- http://<external ip>/swagger/index.html

- http://<external ip>/actuator



Else, you can curl at the port forward:



```shell

curl localhost:28015/actuator/health



curl "localhost:28015/Payment?amount=100000&rate=2&years=30"

```



When you run the payment service with an in-memory cache, the hit counter will start at 1.



### Run the Application in Kubernetes with Redis



(This can be done in Kind)



Install cert manager:



```shell

kubectl apply -f https://github.com/cert-manager/cert-manager/releases/download/v1.15.2/cert-manager.yaml

```



Install the service binding operator:



```shell

kubectl apply -f https://github.com/servicebinding/runtime/releases/download/v1.0.0/servicebinding-runtime-v1.0.0.yaml

```



Install Redis - we're using the Bitnami helm chart here because it will create the secret needed for the service binding:



```shell

helm install my-redis oci://registry-1.docker.io/bitnamicharts/redis \

  --set serviceBindings.enabled=true,architecture=standalone,auth.enabled=false 

```



Deploy app with Redis (you will need to change the image link for your registry):



```shell

kubectl apply -f Kubernetes/deployment-redis.yaml

```



Add the service binding to Redis:



```shell

kubectl apply -f Kubernetes/serviceBinding.yaml

```



If you have a load balancer service available, then:



```shell

kubectl apply -f Kubernetes/service.yaml

```



Else:



```shell

kubectl port-forward deployment/payment-calculator 28015:8080

```



Test URLs:



If you have a LoadBalancer, you can hit the following URLs:



- http://<external ip>/swagger/index.html

- http://<external ip>/actuator



Else, you can curl at the port forward:



```shell

curl localhost:28015/actuator/health



curl "localhost:28015/Payment?amount=100000&rate=2&years=30"

```



When you run the payment service with an in-memory cache, the hit counter will start at 5000.



## Redis Debug



Run redis command line in Docker:



```shell

kubectl run redis-cli -it --image=redis --restart=Never --rm=true -- sh



redis-cli -h my-redis-master -p 6379

```