This repository contains time measurements of different ways to call logger methods in Kotlin.
Calling log with string parameter is the worst way to log. String value is calculated regardless of active log level.
log.trace("it=$it random=${Random()}")
Calling log method with template and separate parameters is much better. toString() method of each provided parameter is called depending on active log level. However object instance itself still has to be created in order to be passed as a parameter.
log.trace("it={} random={}", it, Random())
Lambda calls like this (note curly braces {} instead of ()) is the best way. Object instances specified inside lambda block are not created if active log level does not match.
log.trace { "it=${it} random=${Random()}" }
Unfortunately lambda calls are only available for log4j, not for logback.
There is yet another option that works with both log4j and logback - surround log call with if statement.
Looks ugly but performs very well.
if (log.isTraceEnabled) { log.trace("it=$it random=${Random()}") }
11:48:48.816 [Test worker] ERROR logStringIf - iterations: 100000000 time: 95 ms
11:48:53.760 [Test worker] ERROR logTemplate - logTemplate iterations: 100000000 time: 4940 ms
11:49:16.937 [Test worker] ERROR logString - logString iterations: 100000000 time: 23175 ms
https://github.com/ludenus/test-log/blob/master/test-log4j/app/src/test/kotlin/test/log4j/LogTest.kt
11:47:11.963 [Test worker] ERROR logStringIf - iterations: 100000000 time: 179 ms
11:47:17.149 [Test worker] ERROR logTemplate - iterations: 100000000 time: 5180 ms
11:47:17.588 [Test worker] ERROR logLambda - iterations: 100000000 time: 435 ms
11:47:39.613 [Test worker] ERROR logString - iterations: 100000000 time: 22024 ms