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https://issues.apache.org/jira/browse/LOG4J2-1369?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15246060#comment-15246060
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Remko Popma commented on LOG4J2-1369:
-------------------------------------
Yes, I suspect that simply passing the correct String to the Commons
CompressAction will solve this issue. I also believe the same typo was made
multiple times. I don't think renaming the XY enum value will cause any
problems.
> "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
> Labels: trivial
>
> _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=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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