Log File does not generate complete logs although execution gets completed - file

Question

Please excuse me for a long post.
I am a newbie in logging implementations and I'm trying to read a log file which gets overwritten every time the build is run. The log file contains details of some workflow execution steps.
Configurations for log4j2.xml file :-
<appenders>
<File name="InfoLog" fileName="build/var/debug.log" bufferedIO="true" immediateFlush="false" append="false">
<PatternLayout pattern="%d{yyyy-MM-dd HH:mm:ss.SSS z}{UTC} ~ [%t] ~ %-5level ~ %logger{1} ~ %msg%n"/>
</File>
</appenders>
<loggers>
<Root level="Debug">
<AppenderRef ref="InfoLog"/>
</Root>
</loggers>
An example code snippet for my logger implementation :-
Note → I have api calls to other services and require those logs too
in my file, hence I used mu.KLogging library as it made it super
easy. I wasn’t able to get the logs from calls to other apis, using
java.util.logging or org.apache.log4j libraries.
import mu.KLogging
interface TestsLogger {
companion object {
val logger = KLogging().logger(" WORKFLOW STEPS ")
}
}
//In some class
logger.info { "Running ${(workflowMap.currentStep).toUpperCase()}" }
logger.error { workflowExecutionException }
Now, when I am trying to read the debug.log file (a few seconds after all steps have been executed), for some reason, not all logs are being read from the file.
TimeUnit.MILLISECONDS.sleep(5_000)
var lines: List<String> = Files.readAllLines(File("build/var/debug.log").toPath())
On diving deep into the cause of such behaviour, I found out that, when it tries to read the debug.log file, at that moment the log file does not have all the logs in it. For some reason, last few lines of the logs get appended to file at the moment, when my build gets complete. Although, the executions have already been happened for which I need information from the logs.
FYI -> I am using Gradle Build in Intellij
I am trying to understand why this strange behaviour? And how can I solve it such that logs are
generated correctly and my file reads all the logs generated till that moment ?

Answer 1

You have bufferedIo set to true and immediateFlush set to false. This is good for performance in long running apps that write logs frequently, but for an application that doesn't write much it means the log events will be sitting in a buffer waiting to be written. The buffers should be flushed at application shutdown, unless it is killed or has some other terminal error that doesn't allow it to terminate normally.