Licensing of org.opensearch.core.common.logging.LoggerMessageFormat.java

[ker2x]

While documenting code i noticed that :
libs/core/src/main/java/org/opensearch/core/common/logging/LoggerMessageFormat.java

is an almost identical copy of :
https://github.com/qos-ch/slf4j/blob/master/slf4j-api/src/main/java/org/slf4j/helpers/MessageFormatter.java
which is under the MIT License.

It's pretty much a non-issue since, as far as i know, it's not forbidden by the MIT License. But i'm not a licensing expert.

This code have both elasticsearch and opensearch license header (both Apache 2.0)

I wanted to add this in the javadoc :

/**
 * Format string for OpenSearch log messages.
 * <p>
 * This class is almost a copy of {@code org.slf4j.helpers.MessageFormatter}<p>
 * The original code is licensed under the MIT License and is available at :
 * <a href="https://github.com/qos-ch/slf4j/blob/7c164fab8d54f823dd55c01a5a839c153f578297/slf4j-api/src/main/java/org/slf4j/helpers/MessageFormatter.java">MessageFormatter.java</a>
 *
 * @opensearch.internal
 */

but it's a little bit weird to have this in the javadoc and i'd appreciate some feedback.

Thank you.

[ker2x]

added to #9976
The licensing issue in itself may or may not be a problem.

[dblock]

None of as are licensing experts, but I know someone who is. Let me figure out the right thing to do here.

[hyandell]

Digging into this, it looks like there was a 2010 fork of code from sfl4j that went on quite a journey from there. Kudos to GitHub for letting me walk back through the codebases, this stuff gets ugly when you can't easily skip back along file renames :)

MIT doesn't add any additional conditions to OpenSearch (for example it's on the ASF's Category A list on https://www.apache.org/legal/resolved.html), but the original source header should have been maintained to the forked files.

Action item on me to propose a source header update.

[hyandell]

Okay, here's the proposed license header:

/*
 * This code is based on code from SFL4J 1.5.11
 * Copyright (c) 2004-2007 QOS.ch
 * All rights reserved.
 * SPDX-License-Identifier: MIT
 */

The original commit that introduced this was elastic/elasticsearch@bda476e

While many files were affected then, it looks like https://github.com/opensearch-project/OpenSearch/blob/main/libs/core/src/main/java/org/opensearch/core/common/logging/LoggerMessageFormat.java is the descendant of these files today.

[dblock]

Thanks for PRing it @hyandell.

[ker2x]

Nice ! thx !