[ 
https://issues.apache.org/jira/browse/LOG4J2-1369?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Alex Birch updated LOG4J2-1369:
-------------------------------
    Description: 
_Note: see [associated StackOverflow 
problem](https://stackoverflow.com/questions/36695617/enabling-lzma2-i-e-xz-compression-in-log4j2)_

== 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}

== Goal

I would like to switch to LZMA(2) (i.e. `.xz`) compression, to enjoy an 
improved compression ratio.

== 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}

== Result

When the RollingFileAppender is triggered: the archive created is indeed 
_named_ `engines.log.1.xz` — as required.

**However**, its contents are incorrect:

=== Expectation

`engines.log.1.xz` should contain LZMA(2) compressed text

=== Actual

`engines.log.1.xz` instead contains plain, uncompressed text.

== Sanity checks

I confirm that the `org.tukaani:xz` and `org.apache.commons:commons-compress` 
successfully made it into the classpath of my jar:

```
🍔 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/
...
```

This Java program is not deployed to a J2EE webserver. I believe its class 
loading is straightforward.

== 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

== 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}

  was:
_Note: see [associated StackOverflow 
problem](https://stackoverflow.com/questions/36695617/enabling-lzma2-i-e-xz-compression-in-log4j2)_

== Current state of world

Currently our `RollingFileAppender` in `log4j2.xml` uses Gzip compression:

```
<RollingFile name="RollingFile"
             fileName="logs/engine.log"
             filePattern="logs/engine.log.%i.gz">
```

== Goal

I would like to switch to LZMA(2) (i.e. `.xz`) compression, to enjoy an 
improved compression ratio.

== 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`:

```
<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>
```

== Result

When the RollingFileAppender is triggered: the archive created is indeed 
_named_ `engines.log.1.xz` — as required.

**However**, its contents are incorrect:

=== Expectation

`engines.log.1.xz` should contain LZMA(2) compressed text

=== Actual

`engines.log.1.xz` instead contains plain, uncompressed text.

== Sanity checks

I confirm that the `org.tukaani:xz` and `org.apache.commons:commons-compress` 
successfully made it into the classpath of my jar:

```
🍔 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/
...
```

This Java program is not deployed to a J2EE webserver. I believe its class 
loading is straightforward.

== 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

== 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`:
```
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);
        }
    }
}
```


> "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)_
> == 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}
> == Goal
> I would like to switch to LZMA(2) (i.e. `.xz`) compression, to enjoy an 
> improved compression ratio.
> == 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}
> == Result
> When the RollingFileAppender is triggered: the archive created is indeed 
> _named_ `engines.log.1.xz` — as required.
> **However**, its contents are incorrect:
> === Expectation
> `engines.log.1.xz` should contain LZMA(2) compressed text
> === Actual
> `engines.log.1.xz` instead contains plain, uncompressed text.
> == Sanity checks
> I confirm that the `org.tukaani:xz` and `org.apache.commons:commons-compress` 
> successfully made it into the classpath of my jar:
> ```
> 🍔 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/
> ...
> ```
> This Java program is not deployed to a J2EE webserver. I believe its class 
> loading is straightforward.
> == 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
> == 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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