├── project.clj ├── src └── hey │ └── core.clj ├── perf.sh ├── Dockerfile ├── README.md └── LICENSE /project.clj: -------------------------------------------------------------------------------- 1 | (defproject hey "0.0.1" 2 | :dependencies [[org.clojure/clojure "1.9.0"] 3 | [http-kit "2.1.18"]] 4 | :plugins [[lein-jlink "0.2.0"]] 5 | 6 | ; -- todo cleanup: some of these might be redundant due to testing with ring/jetty 7 | :jlink-modules ["java.base" "java.logging" "java.sql" "java.naming" "java.desktop" "java.xml.bind"] 8 | 9 | ;; java.xml.bind belongs to J2EE and is not included in the SE JDK 10 | :jvm-opts ["--add-modules" "java.xml.bind"] 11 | :aot :all 12 | :main hey.core) 13 | -------------------------------------------------------------------------------- /src/hey/core.clj: -------------------------------------------------------------------------------- 1 | (ns hey.core 2 | (:gen-class) 3 | (:require [org.httpkit.server :as s])) 4 | 5 | (defn handler [my-name request] 6 | {:status 200 7 | :headers {"Content-Type" "text/html"} 8 | :body (format "Hello %s from Clojure, Docker, and Kubernetes." my-name)}) 9 | 10 | (defn -main [& args] 11 | (let [my-name (or (System/getenv "MY_NAME") 12 | "World") 13 | port (or (try (Long/parseLong (System/getenv "PORT")) (catch Exception _)) 14 | 3000)] 15 | (s/run-server (partial handler my-name) {:port port}))) 16 | -------------------------------------------------------------------------------- /perf.sh: -------------------------------------------------------------------------------- 1 | measure() { 2 | DELTA=0.01 3 | tm=0.0 4 | while kubectl get pods --selector $1 | grep "Pending"; do 5 | sleep "${DELTA}s"; 6 | tm=$(echo $tm + $DELTA); 7 | done 8 | 9 | echo $tm 10 | } 11 | 12 | delete() { 13 | running=$(kubectl get pods --selector $1 | grep "Running" | cut -d" " -f 1) 14 | kubectl delete pod $running >/dev/null 2>/dev/null; 15 | } 16 | 17 | doperf() { 18 | for i in $(seq 1 $1); do 19 | echo $(measure "name=hello-clj") 20 | delete "name=hello-clj"; 21 | done 22 | } 23 | 24 | echo $(doperf $1) -------------------------------------------------------------------------------- /Dockerfile: -------------------------------------------------------------------------------- 1 | FROM openjdk:10-jdk as build 2 | 3 | ENV LEIN_VERSION=2.8.1 4 | ENV LEIN_INSTALL=/usr/local/bin/ 5 | 6 | WORKDIR /tmp 7 | 8 | # Download the whole repo as an archive 9 | RUN mkdir -p $LEIN_INSTALL \ 10 | && wget -q https://raw.githubusercontent.com/technomancy/leiningen/$LEIN_VERSION/bin/lein-pkg \ 11 | && mv lein-pkg $LEIN_INSTALL/lein \ 12 | && chmod 0755 $LEIN_INSTALL/lein \ 13 | && wget -q https://github.com/technomancy/leiningen/releases/download/$LEIN_VERSION/leiningen-$LEIN_VERSION-standalone.zip \ 14 | && wget -q https://github.com/technomancy/leiningen/releases/download/$LEIN_VERSION/leiningen-$LEIN_VERSION-standalone.zip.asc \ 15 | && rm leiningen-$LEIN_VERSION-standalone.zip.asc \ 16 | && mkdir -p /usr/share/java \ 17 | && mv leiningen-$LEIN_VERSION-standalone.zip /usr/share/java/leiningen-$LEIN_VERSION-standalone.jar 18 | 19 | RUN wget https://github.com/oracle/graal/releases/download/vm-1.0.0-rc1/graalvm-ce-1.0.0-rc1-linux-amd64.tar.gz 20 | RUN tar zxvf graalvm-ce-1.0.0-rc1-linux-amd64.tar.gz 21 | # Leave some time for tar and coker to catch up, do something else... 22 | RUN apt-get update && \ 23 | apt-get -y install \ 24 | gcc \ 25 | zlib1g-dev 26 | # ..before returning to grall processing 27 | RUN mv graalvm-1.0.0-rc1 /opt/graal && \ 28 | rm graalvm-ce-1.0.0-rc1-linux-amd64.tar.gz 29 | 30 | ENV PATH=$PATH:$LEIN_INSTALL 31 | ENV LEIN_ROOT 1 32 | 33 | RUN mkdir -p /usr/src/app 34 | WORKDIR /usr/src/app 35 | COPY . /usr/src/app 36 | 37 | RUN lein jlink init 38 | RUN lein jlink assemble 39 | 40 | RUN /opt/graal/bin/native-image -H:+ReportUnsupportedElementsAtRuntime -cp target/jlink/hey.jar hey.core 41 | 42 | #NOTE: If you run jlink on ubuntu, you can't use the same jre on alpine, they have incompatible libc libraries! 43 | 44 | FROM debian:sid-slim 45 | 46 | RUN mkdir -p /opt/hey 47 | COPY --from=build /usr/src/app/hey.core /opt/hey 48 | 49 | ENTRYPOINT /opt/hey/hey.core 50 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # clj-on-k8s-quickstart 2 | 3 | Minimal HttpKit web server compiled into a 10 MB dockerized native binary. 4 | 5 | ## Relevance 6 | 7 | As somebody who used to be a hardcore systems guy but fell into the comfort 8 | and nicety of the JVM and later on the joy of Clojure, I have always been 9 | interested in a systems-oriented Clojure version (call it LLVM-Clojure, 10 | Clojure to C, whatever), which in itself is somewhat contradictory since 11 | the garbage collection and memory allocation that the JVM (very efficiently) 12 | does for us must be reimplemented. Expectedly, maybe because of the previous 13 | reason, no such Clojure systems implementation exists yet. 14 | 15 | [Graal](https://github.com/oracle/graal) has made a way possible. And probably, 16 | the best possible way. 17 | 18 | No wonder Clojure communities are excited over this. Graal, with its `native-image` 19 | tool compiles bytecode to native machine versions, embedding the JVM and your code 20 | into a single binary native file that can be handled directly by the OS. 21 | 22 | The next question is the need to reduce the size of the final executable. Enters 23 | Java 10 and its modules. So I started working, 24 | forked from [clj-on-k8s-quickstart](https://github.com/jwhitlark/clj-on-k8s-quickstart) 25 | and built on top of it. 26 | 27 | The product is a dockerized native webserver implemented in Clojure with 28 | all the abstraction it provides which stats up with no down time. 29 | 30 | ## Instructions 31 | 32 | * Build your Docker image 33 | 34 | ```bash 35 | docker image build -t clj-on-k8s/hey:0.0.2 . 36 | ``` 37 | 38 | * Assuming you have a Kubernetes set up (and the image placed in the 39 | correct ECR) 40 | 41 | ```bash 42 | kubectl run hello-clj --image clj-on-k8s/hey:0.0.2 --port 3000 --env="MY_NAME=Clojure" --labels name=hello-clj 43 | ``` 44 | 45 | This works for Minikube. This should also work in vanilla Docker. 46 | 47 | * Connect to the web server inside the container 48 | ```bash 49 | kubectl port-forward $(kubectl get pods --no-headers -o name --selector "name=hello-clj") 3000:3000 50 | ``` 51 | 52 | ## Goals and Rational 53 | 54 | ### [Original goals](https://github.com/jwhitlark/clj-on-k8s-quickstart) 55 | 56 | It's an exciting time. 57 | 58 | Clojure has always been a clean and powerful language with nice interop with the JVM 59 | 60 | Clojure.spec has added exciting capabilities that are very relevant to microservices. 61 | 62 | With JDK9, the JVM has become modular, allowing us to greatly shrink the size of our images. 63 | 64 | With JDK10, the JVM has become a much better docker citizen. 65 | 66 | With Kubernetes, we now have a great platform to build microservices on. 67 | 68 | Istio on K8s gives us new ways to easily visualize, monitor and trace our traffic flows between services. It also simplifies many security tasks, and gives us new abilities to control traffic. 69 | 70 | ### Extra goals 71 | 72 | Graal makes it possible extra-fast native Clojure programs 73 | 74 | 75 | ## Important changes 76 | 77 | I needed to switch from Ring/Jetty to HttpKit because of an Eclipse project 78 | class not found by Graal that I could not resolve. The class was indeed present 79 | in the produced Jar, but it looks like a more general problem with Graal. The 80 | Eclipse ecosystem is apparently affected by this. 81 | 82 | Also I needed to get rid of several cryptographic signature checks that I had no time to fix. 83 | 84 | 85 | ## Thanks! 86 | 87 | * [The original work](https://github.com/jwhitlark/clj-on-k8s-quickstart) and trainsitively those thanked there. 88 | * [Graal team](https://github.com/oracle/graal) 89 | * The guys on the [Clojure subreddit](https://www.reddit.com/r/Clojure/) 90 | * ... and many more!!! -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | 2 | Apache License 3 | Version 2.0, January 2004 4 | http://www.apache.org/licenses/ 5 | 6 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 7 | 8 | 1. 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