StatusLogger: Write to stderr by default #3666
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ppkarwasz
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May 15, 2025
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`StatusLogger` messages used to be written to stderr by default. Since 2.23.0, they are being written to stdout. This is a significant regression. As a rule, stderr is for humans, and stdout is for programs. The pipe operator redirects stdout by default, and a CLI utility can have its output corrupted because Log4j2 emitted a status message to stdout. For example, consider a program that emits JSON and has its output piped to `jq`: after upgrading to Log4j 2.23.0 or later, this program will cease to work correctly unless the StatusLogger is reconfigured to not emit anything, or is explicitly configured to write to stderr. This regression can be fixed by calling the two-parameter constructor variant of `StatusConsoleListener` from `StatusLogger`. A simple test case has been added that captures stdout/stderr and ensures that the default `StatusLogger` is not emitting anything to stdout. Fixes apache#3665.
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StatusLoggermessages used to be written to stderr by default. Since 2.23.0, they are being written to stdout. This is a significant regression. As a rule, stderr is for humans, and stdout is for programs. The pipe operator redirects stdout by default, and a CLI utility can have its output corrupted because Log4j2 emitted a status message to stdout. For example, consider a program that emits JSON and has its output piped tojq: after upgrading to Log4j 2.23.0 or later, this program will cease to work correctly unless the StatusLogger is reconfigured to not emit anything, or is explicitly configured to write to stderr.This regression can be fixed by calling the two-parameter constructor variant of
StatusConsoleListenerfromStatusLogger. A simple test case has been added that captures stdout/stderr and ensures that the defaultStatusLoggeris not emitting anything to stdout.Fixes #3665.