Disallowing the dynamic loading of agents by default

[Rafael Winterhalter]

I try to be supportive of the rather disruptive changes that Java 9
introduces but this one would really do more harm than good.

I work a lot with customers that build tools, many of them would be
affected by this change in a negative way. Did you evaluate the use of the
dynamic attachment API? Dynamic attachment has been around for more than
ten years and you are attempting to cripple this feature in a footnote. I
really believe that you are underestimating the impacts of this change.

The entire point of a Java agent is to attach to a process after it was
already started. I know of numerous use cases where the need for an agent
is only discovered after a Java process is already running and the
attachment is used as a means to adjusting a process without restarting it.
And please bear in mind that tools departments or vendors do often not
control the deployment procedure for Java processes and cannot dicatate
start-up parameters as the one you suggest. It is an important feature of a
Java agent to work independently of the JVM's deployment which you are
taking away. (This is in particularly true for microservice setups where
there are too many JVMs and not interfering with the deployment supports
dev-ops culture.)

Security was always a big argument for justifing these change but as
dynamic attachment requires running as the same user, there is no security
benefit to gain in this context. And I do not see how the integrity
argument adds a notable benefit.

Migrating to Java 9 is already imposing a big challange and this change
will make it even harder. Please do not add this constraint.