To test, start a server, hit a URL, edit the CF code to cause a recompile and hit the same URL again in the browser. Update 242 to java 8 when using a JRE breaks the JVM attach process necessary for instrumentation to work. Using a JDK does not produce the error. Rolling back to Java 8 update 232 also does not error. The issue only happens on a JRE that is Java 8 specifically update 242.
I've seen a number of reports come in from Lucee users and here are the test I ran just now on Windows 7 with CommandBox.
Lucee 5.2.9 openjdk 8 u242 JDK - Works without error
Lucee 5.2.9 open jdk 8 u242 JRE - Web page errors and is unusable - Instrumentation;no providers installed;com.sun.tools.attach.AttachNotSupportedException
Lucee 5.2.9 OpenJDK 8 u232 JRE - Works without error
Lucee 5.3.4 open jdk 8 u242 JRE - No error in web page, but logs fill with this exception: no providers installed;no providers installed;com.sun.tools.attach.AttachNotSupportedException
Lucee 5.3.4 open jdk 8 u242 JDK - Works without error
I don't know if this is a bug in Java 8 update 242 or an issue with the way Lucee is using the attach provider, but I've does lots of googling and can't find any JDK bugs so I want to document this somewhere since so many Lucee users have been hitting the issue.
Below are the commands in CommandBox to start up each server from above along with the full error from the web context's application log file.