apache/beam

[Feature Request]: Add a native Logging transform to Java SDK

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#38.528 geöffnet am 18. Mai 2026

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P2good first issuejavanew feature

Beschreibung

What would you like to happen?

AFAIK the Java SDK doesn't have an easy utility to print/log the outputs of a PCollection. I've always had to hack something together like:

    rows.apply(MapElements.into(strings()).via(row -> {
      System.out.println("row: " + row);
      return "";
    }));

Would be nice to have an easy utility that can be used like:

    rows.apply(Log.info());

The Python SDK has something like this: https://github.com/apache/beam/blob/26c6ec7cb749d60455c9895aa1be49d5cf552a75/sdks/python/apache_beam/transforms/util.py#L2183-L2197

Issue Priority

Priority: 2 (default / most feature requests should be filed as P2)

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Contributor Guide

Tech Stack
java
Domain
backendobservability
Issue Type
feature
SchwierigkeitGeschätzte Implementierungsschwierigkeit für neue Contributors, von 1 für sehr kleine Änderungen bis 5 für Expertenarbeit.
2
Geschätzte ZeitEin grober Zeitrahmen, um zu recherchieren, zu implementieren, zu testen und einen Pull Request vorzubereiten.
1-3 hours
AktivitätsstatusWie verfügbar das Issue gerade wirkt: frisch, aktiv, stale, blockiert oder wartet auf Maintainer-Input.
active
KlarheitWie klar das Issue die erwartete Änderung, Akzeptanzkriterien und den nächsten Schritt erklärt.
clear
Voraussetzungen
JavaApache Beam basicsBeam PTransform understanding
EinsteigerfreundlichkeitEin Score von 1 bis 100, der schätzt, wie zugänglich dieses Issue für First-Time Contributors ist.
60
Research-Richtung
Examine the Python SDK's Log transform implementation at https://github.com/apache/beam/blob/26c6ec7cb749d60455c9895aa1be49d5cf552a75/sdks/python/apache beam/transforms/util.py#L2183 L2197. Identify the appropriate location for a Java equivalent, likely in sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/. Review existing PTransform patterns like MapElements. Implement a Log class with static methods like Log.info(). Ensure it uses the standard logging framework (SLF4J). Add unit tests.