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Instant Netty startup using GraalVM's Native Image Generation
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README.md

Instant Netty startup using GraalVM's Native Image Generation

The purpose of this repository is to walk you through generating a native executable image from a simple Netty application using the GraalVM native-image tool.

Setting up the development environment

To set up your development environment you first need to download GraalVM. Either the Community Edition or the Enterprise Edition works for the purpose of this example. Note that after downloading a GraalVM release, the native-image tool needs to be installed using gu install native-image. Then you need to set your JAVA_HOME to point to GraalVM.

Now you can run the native-image tool:

> $JAVA_HOME/bin/native-image --help

GraalVM native-image building tool

This tool can be used to generate an image that contains ahead-of-time compiled Java code.
...

Alternatively, you could build native-image from source following the quick start guide.

For compilation native-image depends on the local toolchain, so please make sure: glibc-devel, zlib-devel (header files for the C library and zlib) and gcc are available on your system. On the OS that this demo was tested, Ubuntu 16.04, the following command was required to install zlib-devel, the rest of the dependencies being installed out-of-the-box:

$ sudo apt-get install zlib1g-dev

Setting up the project

For the purpose of this demo we copied the HttpHelloWorldServer example from the netty examples repo.

The example is built with Maven. The pom.xml file declares an svm.jar dependency:

<dependency>
  <groupId>com.oracle.substratevm</groupId>
  <artifactId>svm</artifactId>
  <version>19.2.0</version>
  <scope>provided</scope>
</dependency>

The svm.jar library contains all the code needed to compile the substitutions required for Netty. The other required library, graal-sdk.jar, is automatically added to the classpath when you run the javac command shipped with GraalVM.

Now you can build with:

$ mvn clean package

This will create a jar file with all dependencies embedded.

Run Netty on JVM

On the regular JVM you can run as usual using the java command:

> $JAVA_HOME/bin/java -jar target/netty-svm-httpserver-full.jar
Open your web browser and navigate to http://127.0.0.1:8080/

Run Netty with GraalVM Native Image

To build the native image we use the native-image tool:

> $JAVA_HOME/bin/native-image -jar target/netty-svm-httpserver-full.jar
Build on Server(pid: 17238, port: 45712)
[netty-svm-httpserver-full:17238]    classlist:     826.59 ms
[netty-svm-httpserver-full:17238]        (cap):     749.50 ms
[netty-svm-httpserver-full:17238]        setup:   1,375.75 ms
[netty-svm-httpserver-full:17238]   (typeflow):   5,834.62 ms
[netty-svm-httpserver-full:17238]    (objects):   5,493.09 ms
[netty-svm-httpserver-full:17238]   (features):     222.06 ms
[netty-svm-httpserver-full:17238]     analysis:  11,892.85 ms
[netty-svm-httpserver-full:17238]     (clinit):     188.83 ms
[netty-svm-httpserver-full:17238]     universe:     433.88 ms
[netty-svm-httpserver-full:17238]      (parse):     519.48 ms
[netty-svm-httpserver-full:17238]     (inline):   1,110.96 ms
[netty-svm-httpserver-full:17238]    (compile):  10,625.70 ms
[netty-svm-httpserver-full:17238]      compile:  12,985.27 ms
[netty-svm-httpserver-full:17238]        image:     910.28 ms
[netty-svm-httpserver-full:17238]        write:     185.13 ms
[netty-svm-httpserver-full:17238]      [total]:  28,682.93 ms

This creates an executable file that is abut 11 MByte in size:

> ls -Gg --block-size=k netty-svm-httpserver-full
-rwxrwxr-x 1 11328K Aug 26 20:48 netty-svm-httpserver-full

We can now run the executable:

> ./netty-svm-httpserver-full
Open your web browser and navigate to http://127.0.0.1:8080/
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