Add support for concatenated plugin caches #2887
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`Log4j2Plugins.dat` descriptors cause problems while shading an application that uses Log4j Core, since they need a specialized resource transformer to be merged. We maintain such a resource transformer for the Maven Shade Plugin and Gradle Up Shadow also contains a similar tool. Both of them have open issues. The remaining shading build tools, such as SBT Assembly, however, don't have any resource transformer capable of dealing with the `Log4j2Plugins.dat` format. This PR extends the `Log4j2Plugins.dat` format to allow it to contain `\n`-separated lists of serialized `PluginCache` objects. This will allow users to merge plugin caches using more standard tools.
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Together with this PR, we will have 3 plugin descriptor formats:
Can we instead backport I understand the temptation for this easy fix and I am aware that backporting
Last minute edit: Though backporting |
vy
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enhancement
There is no pressing need for this PR, I only created it as a response to this I find shading a bad practice too:
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While I like the I agree with Volkan here that having three formats is not ideal, and even two formats is annoying enough (I had hoped to eliminate support for the .dat format in 3.0, but that's the only thing that allows for 2.x plugins to still be loadable due to annotation changes). Could we have some sort of compromise where the .dat parser can work in a lax mode or something where it tries to continue parsing a concatenated .dat file? |
That is exactly what this PR does: the |
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Even though I find it helpful, I am not in favor of this hack relaxed-mode for following reasons:
- PR is developed in response to a user trying to implement a JTL pretty-printer in a shaded application built using SBT. This is wrong in two major ways:
- She is doing wrong by trying to pretty-print JTL (already explained this to her)
- She is doing wrong by using shading
- PR further complicates the officially accepted Log4j plugin descriptor file format
- We haven't received a single legitimate complaint from SBT users. I don't see a pressing need. This is important and a sensitive point, in particular, given Log4j is known for its bloat. We already massively revamped the docs. Let's first collect some user feedback before settling down on a solution.
These said, PR is technically sound. If there is a consensus from other maintainers to get this in, I won't stop in the way.
| == Merging plugin descriptors | ||
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| The plugin descriptor is located in a JAR file at the following fixed location: | ||
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| You can use the | ||
| https://github.com/GradleUp/shadow/blob/main/src/main/groovy/com/github/jengelman/gradle/plugins/shadow/transformers/Log4j2PluginsCacheFileTransformer.groovy[`Log4j2PluginsCacheFileTransformer`]. | ||
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| * Since version `2.24.0` you can any resource transformer capable of concatenating files using `\n` as separator. |
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| * Since version `2.24.0` you can any resource transformer capable of concatenating files using `\n` as separator. | |
| * Since version `2.24.0`, you can employ any resource transformer capable of concatenating files using `\n` as separator. |
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| assertThat(actual) | ||
| .as("Deserialized plugin cache") | ||
| .isEqualTo(createSampleCache().getAllCategories()); |
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Nit: I'd prefer createSampleCache() accept categories and entries, instead of assuming hardcoded values will be identical in multiple places.
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I agree with Volkan still. No strong feelings from me on whether we should support this. |
Although I am the author of the PR, I also agree with Volkan. So we have consensus! |
Log4j2Plugins.datdescriptors cause problems while shading an application that uses Log4j Core, since they need a specialized resource transformer to be merged.We maintain such a resource transformer for the Maven Shade Plugin and Gradle Up Shadow also contains a similar tool. Both of them have open issues.
The remaining shading build tools, such as SBT Assembly, however, don't have any resource transformer capable of dealing with the
Log4j2Plugins.datformat.This PR extends the
Log4j2Plugins.datformat to allow it to contain\n-separated lists of serializedPluginCacheobjects.This will allow users to merge plugin caches using more standard tools.