Logs creation in parallel test execution
TestNG has it's own custom logging framework similar. To control testNG logging you can add "log4testng.properties" to your classpath.
However as per documentation, there is no way to specify appenders or to control logging programmatically.
For logs which are not from TestNG you can use other logging framework than TestNG's default, like log4J. In that case refer similar question using-different-log-files-for-every-thread-created