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Create Hello World program with Kotlin (#381) 

* Create Hello World program with Kotlin

* Modify Readme by addressing Grant's comments

* Update to gradle official image

* Update dockerfile by addressing ivan's comment

* Read port from env by addressing samodell's comment

* Update Readme by addressing samodell's comment

* svc->service
This commit is contained in:
Zhiming Peng 2018-10-26 11:34:32 -07:00 committed by Knative Prow Robot
parent 70455a3cda
commit c9430eece7
6 changed files with 294 additions and 1 deletions
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serving/samples/README.md
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| Name | Description | Languages |
| ---- | ----------- |:---------:|
| Hello World | A quick introduction that highlights how to deploy an app using Knative Serving. | [C#](helloworld-csharp/README.md), [Clojure](helloworld-clojure/README.md), [Go](helloworld-go/README.md), [Java](helloworld-java/README.md), [Node.js](helloworld-nodejs/README.md), [PHP](helloworld-php/README.md), [Python](helloworld-python/README.md), [Ruby](helloworld-ruby/README.md), [Rust](helloworld-rust/README.md) |
| Hello World | A quick introduction that highlights how to deploy an app using Knative Serving. | [C#](helloworld-csharp/README.md), [Clojure](helloworld-clojure/README.md), [Go](helloworld-go/README.md), [Java](helloworld-java/README.md), [Kotlin](helloworld-kotlin/README.md), [Node.js](helloworld-nodejs/README.md), [PHP](helloworld-php/README.md), [Python](helloworld-python/README.md), [Ruby](helloworld-ruby/README.md), [Rust](helloworld-rust/README.md) |
| Advanced Deployment | Simple blue/green-like application deployment pattern illustrating the process of updating a live application without dropping any traffic. | [YAML](blue-green-deployment.md) |
| Autoscale | A demonstration of the autoscaling capabilities of Knative. | [Go](autoscale-go/README.md) |
| Private Repo Build | An example of deploying a Knative Serving Service using a Github deploy-key and a DockerHub image pull secret. | [Go](build-private-repo-go/README.md) |

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FROM gradle
ADD build.gradle ./build.gradle
ADD src ./src
RUN gradle clean build
ENTRYPOINT ["java","-jar","-Djava.security.egd=file:/dev/./urandom","/home/gradle/build/libs/gradle.jar"]

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# Hello World - Kotlin sample
A simple web app written in Kotlin using [Ktor](https://ktor.io/) that you can use for testing.
It reads in an env variable `TARGET` and prints "Hello ${TARGET}". If
TARGET is not specified, it will use "World" as the TARGET.
## Prerequisites
* A Kubernetes cluster with Knative installed. Follow the
[installation instructions](https://github.com/knative/docs/blob/master/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).
## Steps to recreate the sample code
While you can clone all of the code from this directory, hello world apps are
generally more useful if you build them step-by-step.
The following instructions recreate the source files from this folder.
1. Create a new directory and cd into it:
```shell
mkdir hello
cd hello
```
2. Create a file named `Main.kt` at `src/main/kotlin/com/example/hello` and copy the code block below into it:
```shell
mkdir -p src/main/kotlin/com/example/hello
```
```kotlin
package com.example.hello
import io.ktor.application.*
import io.ktor.http.*
import io.ktor.response.*
import io.ktor.routing.*
import io.ktor.server.engine.*
import io.ktor.server.netty.*
fun main(args: Array<String>) {
val target = System.getenv("TARGET") ?: "World"
val port = System.getenv("PORT") ?: "8080"
embeddedServer(Netty, port.toInt()) {
routing {
get("/") {
call.respondText("Hello $target", ContentType.Text.Html)
}
}
}.start(wait = true)
}
```
3. Switch back to `hello` directory
4. Create a new file, `build.gradle` and copy the following setting
```groovy
buildscript {
ext.kotlin_version = '1.2.61'
ext.ktor_version = '0.9.4'
repositories {
mavenCentral()
}
dependencies {
classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
}
}
apply plugin: 'java'
apply plugin: 'kotlin'
apply plugin: 'application'
sourceCompatibility = 1.8
compileKotlin {
kotlinOptions.jvmTarget = "1.8"
}
compileTestKotlin {
kotlinOptions.jvmTarget = "1.8"
}
repositories {
jcenter()
maven { url "https://dl.bintray.com/kotlin/ktor" }
}
mainClassName = 'com.example.hello.MainKt'
jar {
manifest {
attributes 'Main-Class': mainClassName
}
from { configurations.compile.collect { it.isDirectory() ? it : zipTree(it) } }
}
dependencies {
compile "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
compile "io.ktor:ktor-server-netty:$ktor_version"
testCompile group: 'junit', name: 'junit', version: '4.12'
}
```
5. Create a file named `Dockerfile` and copy the code block below into it.
```docker
FROM gradle
ADD build.gradle ./build.gradle
ADD src ./src
RUN gradle clean build
ENTRYPOINT ["java","-jar","-Djava.security.egd=file:/dev/./urandom","/home/gradle/build/libs/gradle.jar"]
```
6. 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-kotlin
namespace: default
spec:
runLatest:
configuration:
revisionTemplate:
spec:
container:
image: docker.io/{username}/helloworld-kotlin
env:
- name: TARGET
value: "Kotlin Sample v1"
```
## Build and deploy this 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-kotlin .
# Push the container to docker registry
docker push {username}/helloworld-kotlin
```
2. 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 -f service.yaml
```
3. Now that your service is created, Knative will perform 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).
4. To find the IP address for your service, use
`kubectl get service knative-ingressgateway -n istio-system` to get the ingress IP for your
cluster. If your cluster is new, it may take sometime for the service to get assigned
an external IP address.
```shell
kubectl get service knative-ingressgateway -n istio-system
```
```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
```
5. To find the URL for your service, use
```shell
kubectl get services.serving.knative.dev helloworld-kotlin -o=custom-columns=NAME:.metadata.name,DOMAIN:.status.domain
```
```shell
NAME DOMAIN
helloworld-kotlin helloworld-kotlin.default.example.com
```
6. Now you can make a request to your app to see the result. Replace `{IP_ADDRESS}`
with the address you see returned in the previous step.
```shell
curl -H "Host: helloworld-kotlin.default.example.com" http://{IP_ADDRESS}
```
```shell
Hello Kotlin Sample v1
```
## Remove the sample app deployment
To remove the sample app from your cluster, delete the service record:
```shell
kubectl delete -f service.yaml
```

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buildscript {
ext.kotlin_version = '1.2.61'
ext.ktor_version = '0.9.4'
repositories {
mavenCentral()
}
dependencies {
classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
}
}
apply plugin: 'java'
apply plugin: 'kotlin'
apply plugin: 'application'
sourceCompatibility = 1.8
compileKotlin {
kotlinOptions.jvmTarget = "1.8"
}
compileTestKotlin {
kotlinOptions.jvmTarget = "1.8"
}
repositories {
jcenter()
maven { url "https://dl.bintray.com/kotlin/ktor" }
}
mainClassName = 'com.example.hello.MainKt'
jar {
manifest {
attributes 'Main-Class': mainClassName
}
from { configurations.compile.collect { it.isDirectory() ? it : zipTree(it) } }
}
dependencies {
compile "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
compile "io.ktor:ktor-server-netty:$ktor_version"
testCompile group: 'junit', name: 'junit', version: '4.12'
}

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apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
name: helloworld-kotlin
namespace: default
spec:
runLatest:
configuration:
revisionTemplate:
spec:
container:
image: docker.io/{username}/helloworld-kotlin
env:
- name: TARGET
value: "Kotlin Sample v1"

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serving/samples/helloworld-kotlin/src/main/kotlin/com/example/hello/Main.kt Normal file
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package com.example.hello
import io.ktor.application.*
import io.ktor.http.*
import io.ktor.response.*
import io.ktor.routing.*
import io.ktor.server.engine.*
import io.ktor.server.netty.*
fun main(args: Array<String>) {
val target = System.getenv("TARGET") ?: "World"
val port = System.getenv("PORT") ?: "8080"
embeddedServer(Netty, port.toInt()) {
routing {
get("/") {
call.respondText("Hello $target", ContentType.Text.Html)
}
}
}.start(wait = true)
}