How netty supports native-image ?

[yswdqz]

Hi team.

My project uses netty4 and graal-metadata-repository. When I try to compile with native-image, I find that it doesn't work. This may be related to the fact that my project uses the maven shade plugin. I have shaded the metadata-repository configuration as well, but it still doesn't work. So I'm wondering if there are other configurations of netty that are broken by the maven shade plugin?

[chrisvest]

If you can try it out without shading Netty, and see how it goes, I think that would be a good experiment to make.

[yswdqz]

Thank you for your help ! I will take a try later.

By the way, I found that there are also some configuration files that are not part of the metadata-repository (such as native-image.properties) that are in the native-image folder, is that normal?

[violetagg]

@yswdqz I don't have experience with the shaded graalvm reachability metadata repository, but when it is not shaded I can see this

[INFO] Downloaded GraalVM reachability metadata repository from file:/.../.m2/repository/org/graalvm/buildtools/graalvm-reachability-metadata/0.9.23/graalvm-reachability-metadata-0.9.23-repository.zip
[INFO] [graalvm reachability metadata repository for io.netty:netty-buffer:4.1.94.Final]: Configuration directory not found. Trying latest version.
[INFO] [graalvm reachability metadata repository for io.netty:netty-buffer:4.1.94.Final]: Configuration directory is io.netty/netty-buffer/4.1.80.Final
[INFO] [graalvm reachability metadata repository for io.netty:netty-common:4.1.94.Final]: Configuration directory not found. Trying latest version.
[INFO] [graalvm reachability metadata repository for io.netty:netty-common:4.1.94.Final]: Configuration directory is io.netty/netty-common/4.1.80.Final
[INFO] [graalvm reachability metadata repository for io.netty:netty-codec-http:4.1.94.Final]: Configuration directory not found. Trying latest version.
[INFO] [graalvm reachability metadata repository for io.netty:netty-codec-http:4.1.94.Final]: Configuration directory is io.netty/netty-codec-http/4.1.80.Final
[INFO] [graalvm reachability metadata repository for io.netty:netty-transport:4.1.94.Final]: Configuration directory not found. Trying latest version.
[INFO] [graalvm reachability metadata repository for io.netty:netty-transport:4.1.94.Final]: Configuration directory is io.netty/netty-transport/4.1.80.Final
[INFO] [graalvm reachability metadata repository for io.netty:netty-codec-http2:4.1.94.Final]: Configuration directory not found. Trying latest version.
[INFO] [graalvm reachability metadata repository for io.netty:netty-codec-http2:4.1.94.Final]: Configuration directory is io.netty/netty-codec-http2/4.1.80.Final
[INFO] [graalvm reachability metadata repository for io.netty:netty-handler:4.1.94.Final]: Configuration directory not found. Trying latest version.
[INFO] [graalvm reachability metadata repository for io.netty:netty-handler:4.1.94.Final]: Configuration directory is io.netty/netty-handler/4.1.80.Final
[INFO] [graalvm reachability metadata repository for io.netty:netty-resolver-dns:4.1.94.Final]: Configuration directory not found. Trying latest version.
[INFO] [graalvm reachability metadata repository for io.netty:netty-resolver-dns:4.1.94.Final]: Configuration directory is io.netty/netty-resolver-dns/4.1.80.Final

And then I see that some configurations are excluded when one uses graalvm reachability metadata repository

[INFO] Executing: /.../graalvm-ce-19/Contents/Home/bin/native-image ... 
-H:ConfigurationFileDirectories=/.../target/graalvm-reachability-metadata/3483486ffed5a63ebf85ee5fdefdf41eba5d30d5/io.netty/netty-handler/4.1.80.Final,... 
--exclude-config \Q/.../.m2/repository/io/netty/netty-buffer/4.1.94.Final/netty-buffer-4.1.94.Final.jar\E ^/META-INF/native-image/ 
--exclude-config \Q/.../.m2/repository/io/netty/netty-common/4.1.94.Final/netty-common-4.1.94.Final.jar\E ^/META-INF/native-image/ 
--exclude-config \Q/.../.m2/repository/io/netty/netty-codec-http/4.1.94.Final/netty-codec-http-4.1.94.Final.jar\E ^/META-INF/native-image/ 
--exclude-config \Q/.../.m2/repository/io/netty/netty-transport/4.1.94.Final/netty-transport-4.1.94.Final.jar\E ^/META-INF/native-image/ 
--exclude-config \Q/.../.m2/repository/io/netty/netty-codec-http2/4.1.94.Final/netty-codec-http2-4.1.94.Final.jar\E ^/META-INF/native-image/ 
--exclude-config \Q/.../.m2/repository/io/netty/netty-handler/4.1.94.Final/netty-handler-4.1.94.Final.jar\E ^/META-INF/native-image/ 
--exclude-config \Q/.../.m2/repository/io/netty/netty-resolver-dns/4.1.94.Final/netty-resolver-dns-4.1.94.Final.jar\E ^/META-INF/native-image/

[yswdqz]

Thank you, may be I need to write a transformer to exclude the original config of netty.

But I also have 2 questions:

1. If netty's original config always needed to be removed, why does it still exist?
2. Many frameworks have code similar to NettySubtitutions (such as quarkus), what does it do, and if I want my project to support native-image, do I need to add such code too?

[violetagg]

If netty's original config always needed to be removed, why does it still exist?

Check this #12601

[yswdqz]

Got it. So just for netty4, I also need to write a NettySubtitutions.java to avoid some errors?