Introduction

Many applications send logs to standard error by default, which becomes noisy in shells, pipelines, and monitoring systems that treat stderr as a failure channel. The right fix is usually to reroute or narrow those logs rather than blindly silencing everything.

Understand Why Logs Reach stderr

A lot of runtimes and logging frameworks choose stderr as the default target for console output. That is convenient during development, but it can interfere with:

• shell pipelines that reserve stderr for failures
• monitoring systems that alert on any stderr activity
• command-line tools that need machine-readable stdout

Before changing anything, decide whether you want to:

• move logs to stdout
• send them to files or a collector
• suppress only specific noisy loggers
• discard stderr entirely as a last resort

Those are different operational choices.

Python: Route Logs to stdout

In Python, logging.StreamHandler defaults to stderr unless you provide a stream explicitly.

1import logging
2import sys
3
4logger = logging.getLogger("app")
5logger.setLevel(logging.INFO)
6
7stdout_handler = logging.StreamHandler(stream=sys.stdout)
8stdout_handler.setFormatter(logging.Formatter("%(asctime)s %(levelname)s %(message)s"))
9
10logger.handlers = [stdout_handler]
11logger.propagate = False
12
13logger.info("service started")
14logger.error("error log now also goes to stdout")

This keeps logs visible while freeing stderr for explicit failure output when that distinction matters.

Python: Suppress Only Noisy Libraries

Sometimes the real problem is not your application logger but a third-party library that floods stderr.

1import logging
2
3logging.getLogger("urllib3").setLevel(logging.CRITICAL)
4logging.getLogger("botocore").setLevel(logging.CRITICAL)

Targeted suppression is usually safer than disabling all logging globally.

Java With Logback

In Java services, Logback commonly controls whether console logs go to System.err or System.out.

1<configuration>
2  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
3    <target>System.out</target>
4    <encoder>
5      <pattern>%d{yyyy-MM-dd HH:mm:ss} %-5level %logger - %msg%n</pattern>
6    </encoder>
7  </appender>
8
9  <root level="INFO">
10    <appender-ref ref="STDOUT" />
11  </root>
12</configuration>

Switching the console appender target is usually better than turning the logger off entirely.

Shell-Level Redirection

If you cannot change the application quickly, shell redirection can be a temporary workaround.

Redirect stderr to stdout:

./my_app 2>&1

Discard stderr completely:

./my_app 2>/dev/null

Discarding stderr should be used carefully. It can hide real error diagnostics and make production issues much harder to investigate.

Containers and Observability

In containers, stdout and stderr are often collected separately but both end up in a logging pipeline. Changing which stream logs use can affect downstream parsing, routing, and alerts.

Before rolling out a stream change, verify:

• collector behavior
• alert rules based on stderr
• dashboards that depend on stream labels
• whether crash traces still remain visible

A stream change is an observability change, not just a code cleanup. It can alter alert volume, parser behavior, retention rules, and the way operators distinguish ordinary logs from true failures during an incident.

Common Pitfalls

The biggest mistake is disabling all logging globally and losing incident diagnostics.

Another issue is redirecting stderr to /dev/null in production without another place for errors to go.

A third problem is changing logger streams without updating monitoring rules and then assuming the logging change was harmless. Even a small stream redirect can change how log shippers classify events and how incident responders triage them.

Summary

• stderr logging is often a framework default, not a requirement.
• Prefer rerouting logs to stdout or a file over blind suppression.
• Use framework-specific configuration for a durable fix.
• Treat stream changes as observability changes, not only formatting changes.
• Keep critical failures visible even if routine logs no longer go to stderr.