[jira] [Commented] (LOG4J2-1369) "xz" compression results in plaintext, uncompressed files.

["Remko Popma (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LOG4J2-1369?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15245926#comment-15245926 ] 

Remko Popma commented on LOG4J2-1369:
-------------------------------------

This looks almost like a typo: we wrote "xy" when we should have written "xz". The Commons Compress library likely does not handle xy... 

Can you provide a patch?

> "xz" compression results in plaintext, uncompressed files.
> ----------------------------------------------------------
>
>                 Key: LOG4J2-1369
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-1369
>             Project: Log4j 2
>          Issue Type: Bug
>          Components: Appenders, Core, Documentation
>    Affects Versions: 2.5
>         Environment: Java SE 1.7
>            Reporter: Alex Birch
>
> _Note: see [associated StackOverflow problem|https://stackoverflow.com/questions/36695617/enabling-lzma2-i-e-xz-compression-in-log4j2]_
> h2. Current state of world
> Currently our `RollingFileAppender` in `log4j2.xml` uses Gzip compression:
> {code:xml}
> <RollingFile name="RollingFile"
>              fileName="logs/engine.log"
>              filePattern="logs/engine.log.%i.gz">
> {code}
> h2. Goal
> I would like to switch to LZMA(2) (i.e. `.xz`) compression, to enjoy an improved compression ratio.
> h2. Attempt
> I have tried changing {{engine.log.%i.gz}} to {{engine.log.%i.xz}} — as per [the documentation|https://logging.apache.org/log4j/2.x/manual/appenders.html#DefaultRolloverStrategy]:
> bq. If the file pattern ends with {{.gz}}, {{.zip}}, {{.bz2}}, {{.deflate}}, {{.pack200}}, or {{.xz}} the resulting archive will be compressed using the compression scheme that matches the suffix. The formats bzip2, Deflate, Pack200 and XZ require Apache Commons Compress. In addition, XZ requires [XZ for Java](http://tukaani.org/xz/java.html).
> Additionally I have ensured that I have a runtime dependency on [XZ for Java|http://tukaani.org/xz/java.html] — via {{pom.xml}}:
> {code:xml}
> <dependency>
>     <!-- Support Log4j2 Log compression schemes: ".gz", ".zip", ".bz2", ".deflate", ".pack200", [".xz" (part 1 of 2)] -->
>     <groupId>org.apache.commons</groupId>
>     <artifactId>commons-compress</artifactId>
>     <version>1.11</version>
> </dependency>
> <dependency>
>     <!-- Support Log4j2 Log compression scheme [".xz" (part 2 of 2)] -->
>     <groupId>org.tukaani</groupId>
>     <artifactId>xz</artifactId>
>     <version>1.5</version>
> </dependency>
> {code}
> h2. Result
> When the RollingFileAppender is triggered: the archive created is indeed _named_ `engines.log.1.xz` — as required.
> **However**, its contents are incorrect:
> h3. Expectation
> `engines.log.1.xz` should contain LZMA(2) compressed text
> h3. Actual
> `engines.log.1.xz` instead contains plain, uncompressed text.
> h2. Sanity checks
> I confirm that the `org.tukaani:xz` and `org.apache.commons:commons-compress` successfully made it into the classpath of my jar:
> {code:none}
> 🍔 jar tf mycooljar.jar | grep tukaani
> org/tukaani/
> org/tukaani/xz/
> ...
> 🍔 jar tf mycooljar.jar | grep org/apache/commons/compress
> org/apache/commons/compress/
> org/apache/commons/compress/changes/
> ...
> {code}
> This Java program is not deployed to a J2EE webserver. I believe its class loading is straightforward.
> h2. Summary
> I have correctly followed the instructions necessary to create `.gz` archives.
> I believe the only additional step required to create `.xz` archives is: I must provide at runtime the [XZ for Java](http://tukaani.org/xz/java.html) artefact. I have done this.
> Am I missing something here? I am tempted to believe one of the following:
>  - The functionality is broken
>  - The docs are incomplete/incorrect
>  - log4j2 fails to discover the class at runtime
> h2. Leads so far
> I was able to find [some evidence](https://git-wip-us.apache.org/repos/asf?p=logging-log4j2.git;a=blob;f=log4j-core/src/main/java/org/apache/logging/log4j/core/appender/rolling/DefaultRolloverStrategy.java;h=e3b8ffe3c9a0cf83f4392c17786e8dc47f5046b5;hb=HEAD#l125) that perhaps I am expected to input `.xy` instead of `.xz`. If I use `.xy`: the log4j2 `RollingAppender` fails to produce archives. That is: it creates blank `.xy` files, and retains the unarchived plaintext as a `.log` file. It smells like a buggy implementation.
> Here is the code I present as evidence from `org.apache.logging.log4j.core.appender.rolling.DefaultRolloverStrategy`:
> {code:title=org.apache.logging.log4j.core.appender.rolling.DefaultRolloverStrategy.java|borderStyle=solid}
> static enum FileExtensions {
>     XY(".xy") {
>         @Override
>         Action createCompressAction(final String renameTo, final String compressedName, final boolean deleteSource,
>                  final int compressionLevel) {
>              // One of "gz", "bzip2", "xz", "pack200", or "deflate".
>              return new CommonsCompressAction("xy", source(renameTo), target(compressedName), deleteSource);
>         }
>     }
> }
> {code}



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