[
https://issues.apache.org/jira/browse/HADOOP-18500?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17620550#comment-17620550
]
ASF GitHub Bot commented on HADOOP-18500:
-----------------------------------------
rshkv opened a new pull request, #5045:
URL: https://github.com/apache/hadoop/pull/5045
### Description of PR
Upgrade maven-shade-plugin to 3.3.0. This avoids unnecessary rewrites of
class files during relocation.
### How was this patch tested?
I built Hadoop locally and compared the byte code of the class files before
and after the upgrade. Before, the byte code is different between classes
inside relocated JARs and non-relocated JARs (e.g. in `hadoop-client-runtime`
vs `hadoop-shaded-guava`). After, the byte code is the same.
### For code changes:
- [ ] Does the title or this PR starts with the corresponding JIRA issue id
(e.g. 'HADOOP-17799. Your PR title ...')?
- [ ] Object storage: have the integration tests been executed and the
endpoint declared according to the connector-specific documentation?
- [ ] If adding new dependencies to the code, are these dependencies
licensed in a way that is compatible for inclusion under [ASF
2.0](http://www.apache.org/legal/resolved.html#category-a)?
- [ ] If applicable, have you updated the `LICENSE`, `LICENSE-binary`,
`NOTICE-binary` files?
> Upgrade maven-shade-plugin to 3.3.0
> -----------------------------------
>
> Key: HADOOP-18500
> URL: https://issues.apache.org/jira/browse/HADOOP-18500
> Project: Hadoop Common
> Issue Type: Improvement
> Components: build
> Reporter: Willi Raschkowski
> Assignee: Ashutosh Gupta
> Priority: Minor
>
> Maven-shade-plugin rewrites classes when moving them into {{hadoop-client}}
> JARs. That's true even when it doesn't actually need to modify the byte code
> of the classes, say for shading.
> We use a tool that checks for classpath duplicates that don't have equal byte
> codes. We noticed that it flags classes brought in via Hadoop, where one JAR
> containing them is {{hadoop-client-api}} and {{{}hadoop-client-runtime{}}},
> and the other JAR is {{hadoop-common}} or {{{}hadoop-shaded-guava{}}}. The
> byte code for the same class is indeed different between the relocated and
> non-relocated JARs.
> This is because maven-shade-plugin, before 3.3.0, was rewriting class files
> even when the relocation was a "no-op". See MSHADE-391 and
> [apache/maven-shade-plugin#95|https://github.com/apache/maven-shade-plugin/pull/95].
> {quote}
> Maven Shade internally uses [ASM's
> {{ClassRemapper}}|https://asm.ow2.io/javadoc/org/objectweb/asm/commons/ClassRemapper.html]
> and defines a custom {{Remapper}} subclass, which takes care of relocation,
> partially doing the work by itself and partially delegating to the ASM parent
> class. An ASM {{ClassReader}} reads each class file from the original JAR and
> *unconditionally* writes it into a {{{}ClassWriter{}}}, plugging in the
> transformer.
> This transformation, even if not a single relocation (package name mapping)
> takes place, often leads to binary differences between original class and
> transformed class, because constant pool or stack map frames have been
> adjusted, not changing the functionality of the class, but making it look
> like something changed when comparing class files before and after the
> relocation process.
> {quote}
> Upgrading to maven-shade-plugin 3.3.0 fixes the unnecessary rewrite of
> classes.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
