Controller and Agent stop logging when used with OpenTelemetry Java Agent

We received the following problem report:

Summary

When the JS7 Controller (2.8.3) is started with the OpenTelemetry Java agent (-javaagent:/opt/opentelemetry-javaagent.jar), every log event triggers a java.lang.UnsupportedOperationException: entrySet originating from JS7's own js7.base.log.log4j.Log4jMap.

Environment

• JS7 Controller: 2.8.3
• OpenTelemetry Java agent: 2.29.0
• Log4j: 2.24.3

Root Cause

JS7's Log4jMap intentionally does not implement entrySet():

def entrySet(): util.Set[Map.Entry[String, String]] =
  throw new UnsupportedOperationException("entrySet")

The OpenTelemetry agent's Log4j context-data (MDC) instrumentation injects trace/span context into Log4j's ThreadContext. Log4j's ThreadContextDataInjector then calls HashMap.putMapEntries → Log4jMap.entrySet(), which throws.

Impact

• Log events (ControllerInitialized, ControllerReady, Prometheus /metrics startup, etc.) are not written to the log.
• Appender creation also fails: Could not create plugin ... RollingRandomAccessFileAppender: UnsupportedOperationException: entrySet.
• The controller still starts and becomes ready, but logging is kinda broken while the OTel agent is active.

Steps to Reproduce

1. Start the JS7 Controller with:
   JAVA_OPTIONS=-javaagent:/opt/opentelemetry-javaagent.jar
2. Observe repeated UnsupportedOperationException: entrySet stack traces in the container output.
3. Removing the -javaagent option eliminates the errors.

Workaround

Disable the OTel Log4j context-data injection (tracing/metrics remain functional) by use of the environment variable:
OTEL_INSTRUMENTATION_LOG4J_CONTEXT_DATA_ENABLED=false