Is it possible to use Log4j Kotlin

Question

Is it possible to use Log4j Kotlin <https logging apache org log4j kotlin index html> with Ktor

napperley · Answer

Doesn t seem possible since Ktor doesn t support Log4j 2 slightly frowning face

rocketraman · Answer

Ktor uses slf4j which supports log4j2 as a logging backend That being said I m not sure I really understand your question you can absolutely use log4j2 s kotlin api in your own code thereby having both Ktor and your own logging go to the same backend logging system

napperley · Answer

When I tried to get Log4j 2 working with Ktor the framework wouldn t recognise the library even when the log4j to slf4j library was used

rocketraman · Answer

That s the wrong library `log4j to slf4j` directs log4j logs to slf4j which then use a different logging backend You want `log4j slf4j impl` to direct logging using slf4j to log4j2

napperley · Answer

Tried using log4j slf4j impl however nothing is being logged to the terminal Even Netty log messages aren t being logged

rocketraman · Answer

What does your `log4j2 xml` look like

rocketraman · Answer

You also removed `log4j to slf4j` right I have to ask slightly smiling face

napperley · Answer

Below are the contents of the Log4j 2 configuration file

napperley · Answer

Yes I have removed log4j to slf4j

rocketraman · Answer

Forgeting about ktor for a second do you get logs straight from log4j2

napperley · Answer

No the logs aren t coming through from log4j2

napperley · Answer

Now getting log messages outputted to the console however there are multiple errors appearing about the message format which is strange ``` 2019 02 01 13 31 10 440 main ERROR Unrecognized format specifier p 2019 02 01 13 31 10 441 main ERROR Unrecognized conversion specifier p starting at position 28 in conversion pattern 2019 02 01 13 31 10 442 main ERROR Unrecognized format specifier c 2019 02 01 13 31 10 442 main ERROR Unrecognized conversion specifier c starting at position 34 in conversion pattern 2019 02 01 13 31 10 442 main ERROR Unrecognized format specifier L 2019 02 01 13 31 10 442 main ERROR Unrecognized conversion specifier L starting at position 37 in conversion pattern 2019 02 01 13 31 10 443 main ERROR Unrecognized format specifier m 2019 02 01 13 31 10 443 main ERROR Unrecognized conversion specifier m starting at position 42 in conversion pattern 2019 02 01 13 31 10 443 main ERROR Unrecognized format specifier n 2019 02 01 13 31 10 443 main ERROR Unrecognized conversion specifier n starting at position 44 in conversion pattern ```

napperley · Answer

Wondering if there are class path issues aka Ktor s own version of log4j is interfering with the program s log4j2 <https stackoverflow com questions 44480197 log4j2 error unrecognized format specifier t>

napperley · Answer

Below is the contents of the dependencies block from build gradle kts ``` val kotlinVer = 1 3 20 val ktorVer = 1 1 2 val mariaDbVer = 2 3 0 val jooqVer = 3 10 0 val jacksonKotlinModuleVer = 2 9 6 val log4jVer = 2 11 1 implementation kotlin module = stdlib jdk8 version = kotlinVer implementation io ktor ktor server core $ktorVer implementation io ktor ktor server netty $ktorVer implementation io ktor ktor jackson $ktorVer implementation org apache logging log4j log4j slf4j impl $log4jVer implementation org jooq jooq $jooqVer implementation org mariadb jdbc mariadb java client $mariaDbVer implementation com fasterxml jackson module jackson module kotlin $jacksonKotlinModuleVer ```

rocketraman · Answer

Ktor doesn t have its own version of log4j2 it uses slf4j as stated before I haven t used the properties config in a while but it looks like you might be using a 1 x properties rather than a 2 x properties not the same see Configuration with Properties at <https logging apache org log4j 2 x manual configuration html>

rocketraman · Answer

In any case your issue appears to have nothing to do with Ktor as even straight logging does not work in your environment so you d do better asking on the log4j2 users list