[samples] R sample with R server

community/samples/README.md

@@ -12,9 +12,9 @@ something isn't working, lend a helping hand and fix it in a PR.
 
 Knative Serving sample apps.
 
-| Sample Name | Description                                                                   | Language(s)                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
-| ----------- | ----------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
-| Hello World | A quick introduction to Knative Serving that highlights how to deploy an app. | [Clojure](./serving/helloworld-clojure/README.md), [Dart](./serving/helloworld-dart/README.md), [Elixir](./serving/helloworld-elixir/README.md), [Haskell](./serving/helloworld-haskell/README.md), [Java - Micronaut](./serving/helloworld-java-micronaut/README.md), [Java - Quarkus](./serving/helloworld-java-quarkus/README.md), [Rust](./serving/helloworld-rust/README.md), [Swift](./serving/helloworld-swift/README.md), [Vertx](./serving/helloworld-vertx/README.md) |
+| Sample Name | Description | Language(s) |
+| ----------- | ----------- | ----------- |
+| Hello World | A quick introduction to Knative Serving that highlights how to deploy an app. | [Clojure](./serving/helloworld-clojure/README.md), [Dart](./serving/helloworld-dart/README.md), [Elixir](./serving/helloworld-elixir/README.md), [Haskell](./serving/helloworld-haskell/README.md), [Java - Micronaut](./serving/helloworld-java-micronaut/README.md), [Java - Quarkus](./serving/helloworld-java-quarkus/README.md), [R - Go Server](./serving/helloworld-r/README.md), [R](./serving/hellowolrd-rserver/README.md), [Rust](./serving/helloworld-rust/README.md), [Swift](./serving/helloworld-swift/README.md), [Vertx](./serving/helloworld-vertx/README.md) |
 
 
 #### Eventing and Eventing Resources samples

community/samples/serving/helloworld-rserver/Dockerfile

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+# The official R base image
+# https://hub.docker.com/_/r-base
+FROM r-base:3.6.0
+
+# Copy local code to the container image.
+WORKDIR /usr/src/app
+COPY . .
+
+# Install R packages
+RUN Rscript -e "install.packages('plumber', repos='http://cran.us.r-project.org/')"
+
+# Run the web service on container startup.
+CMD ["Rscript", "server.R"]

community/samples/serving/helloworld-rserver/HelloWorld.R

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+#' HelloWorld function
+#' @get /
+#' @html
+function() {
+  TARGET <- Sys.getenv("TARGET", "World")
+
+  message = paste("Hello ", TARGET, "!", sep = "")
+  print(message)
+}

community/samples/serving/helloworld-rserver/README.md

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+---
+title: "Hello World - R server"
+linkTitle: "R server"
+weight: 1
+type: "docs"
+---
+
+A simple web app created with R package, [plumber](https://www.rplumber.io).
+plumber creates a REST API by adding annotations to your R code. The R script
+reads an environment variable `TARGET` and prints `Hello ${TARGET}!`. If the
+`TARGET` environment variable is not specified, the script uses `World`.
+
+Follow the steps below to create the sample code and then deploy the app to your
+cluster. You can also download a working copy of the sample, by running the
+following commands:
+
+```shell
+git clone -b "{{< branch >}}" https://github.com/knative/docs knative-docs
+cd knative-docs/docs/serving/samples/hello-world/helloworld-r
+```
+
+## Before you begin
+
+- A Kubernetes cluster with Knative installed. Follow the
+  [installation instructions](../../../../install/README.md) if you need to
+  create one.
+- [Docker](https://www.docker.com) installed and running on your local machine,
+  and a Docker Hub account configured (we'll use it for a container registry).
+
+## Recreating the sample code
+
+1. Create a new file named `HelloWorld.R` and paste the following script:
+
+   ```R
+   #' HelloWorld function
+   #' @get /
+   #' @html
+   function() {
+     TARGET <- Sys.getenv("TARGET", "World")
+
+     message = paste("Hello ", TARGET, "!", sep = "")
+     print(message)
+   }
+   ```
+
+   This file defines the endpoint `/`, using plumber annotations.
+
+   1. Create a new file named `server.R` and paste the following code:
+
+      ```R
+      library(plumber) # https://www.rplumber.io/
+
+      # Translate the HelloWorld file into a Plumber API
+      r <- plumb("HelloWorld.R")
+      # Get the PORT env var
+      PORT <- strtoi(Sys.getenv("PORT", 8080))
+      # Run the API
+      r$run(port=PORT, host="0.0.0.0")
+      ```
+
+   1. Create a new file named `Dockerfile` and paste the following code:
+
+      ```docker
+      # The official R base image
+      # https://hub.docker.com/_/r-base
+      FROM r-base:3.6.0
+
+      # Copy local code to the container image.
+      WORKDIR /usr/src/app
+      COPY . .
+
+      # Install R packages
+      RUN Rscript -e "install.packages('plumber', repos='http://cran.us.r-project.org/')"
+
+      # Run the web service on container startup.
+      CMD ["Rscript", "server.R"]
+      ```
+
+
+1. Create a new file, `service.yaml` and copy the following service definition
+   into the file. Make sure to replace `{username}` with your Docker Hub
+   username.
+
+   ```yaml
+   apiVersion: serving.knative.dev/v1alpha1
+   kind: Service
+   metadata:
+     name: helloworld-rserver
+     namespace: default
+   spec:
+     template:
+       spec:
+         containers:
+         - image: docker.io/{username}/helloworld-rserver
+           env:
+           - name: TARGET
+             value: "R Server Sample v1"
+   ```
+
+## Building and deploying the sample
+
+Once you have recreated the sample code files (or used the files in the sample
+folder) you're ready to build and deploy the sample app.
+
+1. Use Docker to build the sample code into a container. To build and push with
+   Docker Hub, run these commands replacing `{username}` with your Docker Hub
+   username:
+
+   ```shell
+   # Build the container on your local machine
+   docker build -t {username}/helloworld-rserver .
+
+   # Push the container to docker registry
+   docker push {username}/helloworld-rserver
+   ```
+
+1. After the build has completed and the container is pushed to docker hub, you
+   can deploy the app into your cluster. Ensure that the container image value
+   in `service.yaml` matches the container you built in the previous step. Apply
+   the configuration using `kubectl`:
+
+   ```shell
+   kubectl apply --filename service.yaml
+   ```
+
+1. Now that your service is created, Knative performs the following steps:
+
+   - Create a new immutable revision for this version of the app.
+   - Network programming to create a route, ingress, service, and load balance
+     for your app.
+   - Automatically scale your pods up and down (including to zero active pods).
+
+1. Run the following command to find the external IP address for your service.
+   The ingress IP for your cluster is returned. If you just created your
+   cluster, you might need to wait and rerun the command until your service gets
+   asssigned an external IP address.
+
+   ```shell
+   kubectl get svc knative-ingressgateway --namespace istio-system
+   ```
+
+   Example:
+
+   ```shell
+   NAME                     TYPE           CLUSTER-IP     EXTERNAL-IP      PORT(S)                                      AGE
+   knative-ingressgateway   LoadBalancer   10.23.247.74   35.203.155.229   80:32380/TCP,443:32390/TCP,32400:32400/TCP   2d
+
+   ```
+
+1. Run the following command to find the domain URL for your service:
+
+   ```shell
+   kubectl get ksvc helloworld-r  --output=custom-columns=NAME:.metadata.name,URL:.status.url
+   ```
+
+   Example:
+
+   ```shell
+   NAME                URL
+   helloworld-r    http://helloworld-r.default.example.com
+   ```
+
+1. Test your app by sending it a request. Use the following `curl` command with
+   the domain URL `helloworld-rserver.default.example.com` and `EXTERNAL-IP`
+   address that you retrieved in the previous steps:
+
+   ```shell
+   curl -H "Host: helloworld-rserver.default.example.com" http://{EXTERNAL_IP_ADDRESS}
+   ```
+
+   Example:
+
+   ```shell
+   curl -H "Host: helloworld-rserver.default.example.com" http://35.203.155.229
+   [1] "Hello R Sample v1!"
+   ```
+
+   > Note: Add `-v` option to get more detail if the `curl` command failed.
+
+## Removing the sample app deployment
+
+To remove the sample app from your cluster, delete the service record:
+
+```shell
+kubectl delete --filename service.yaml
+```

community/samples/serving/helloworld-rserver/server.R

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+library(plumber) # https://www.rplumber.io/
+
+# Translate the HelloWorld file into a Plumber API
+r <- plumb("HelloWorld.R")
+# Get the PORT env var
+PORT <- strtoi(Sys.getenv("PORT", 8080))
+# Run the API
+r$run(port=PORT, host="0.0.0.0")

community/samples/serving/helloworld-rserver/service.yaml

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+apiVersion: serving.knative.dev/v1alpha1
+kind: Service
+metadata:
+  name: helloworld-rserver
+  namespace: default
+spec:
+  template:
+    spec:
+      containers:
+      - image: docker.io/{username}/helloworld-rserver
+        env:
+        - name: TARGET
+          value: "R Server Sample v1"