Symptoms:

In the log, there will be an error that looks similar to the following:

Failed to deserialize event: SystemLogMonitor

This will be followed by a long string, with a caused by that may read:

Caused by: java.lang.reflect.InaccessibleObjectException: Unable to make field private java.lang.String java.lang.Throwable.detailMessage accessible: module java.base does not "opens java.lang" to unnamed module @2525ff7e

Explanation:

With the expanded use of the Java Platform Module System in the newer versions of Java, some of the modules and methods being used by SymmetricDS have begun only allowing access under certain conditions. As a result of this, in the newer versions of Java (15+), SymmetricDS will try to access methods in a way that has not been explicitly allowed within that method's module.

Resolution:

To remedy this, you will add the following to the sym_service.conf on all nodes running Java 15+ and then restart SymmetricDS:

wrapper.java.additional=--add-opens
wrapper.java.additional=java.base/java.lang=ALL-UNNAMED