Quest For "Unbreakable Java" Unites ABAP & Java

jg21 writes "Writing an article about "A Java Server That Never Goes Down" is pure hubris, but a German developer who says he's been "eating, sleeping, and drinking Java" for 8 years doesn't seem to care and his article brings to light the aspects of VM we rarely think of as he introduces "user isolation" and tells about some interesting work SAP in Germany is doing in that area, merging the Java and the ABAP worlds."

Comments

Throw it in jail

[SIGALRM]

Inside the VM, parallelism is implemented using threads with no separation regarding memory or other resources. In this respect Java has not changed since its invention in the early nineties.

I agree that ABAP's dispatcher is an excellent model for per-process isolation. Going further in Java, I would suggest adding a portable root jail to the API. This could allow chroot to isolate and/or run the I/O of native subprocesses through a Java SecurityManager, using a user mode filesystem mechanism. In this way you could secure a Java language service... a handy way of adding a final wrapper to the security provided by the JVM.

So basically...

[bill_mcgonigle]

• run fewer users per VM
• run more VM's
• use "shared closures" (fast oo serialization) to get idle users out of the VM's and,
• use Apple's Shared Classes to reduce memory footprint (needs java 1.5)

This sound like it's at least as much about fast and effective recovery on crash as it is crash prevention. Which to a web user is the same thing.

All VM's have bugs so crash-proof is a tall order.

Crash-only software

[Earlybird]

Ladies and germs, I give you crash-only software.

• Crash-only programs crash safely and recover quickly. There is only one way to stop such software -- by crashing it -- and only one way to bring it up -- by initiating recovery. Crash-only systems are built from crash-only components, and the use of transparent component-level retries hides intra-system component crashes from end users. In this paper we advocate a crash-only design for Internet systems, showing that it can lead to more reliable, predictable code and faster, more effective recovery. We present ideas on how to build such crash-only Internet services, taking successful techniques to their logical extreme.

Check out the Isolation JSR

[AdamInParadise]

There is already a JSR for that would define a standard for Jail-like compartments in a single JVM process:
JSR 121: Application Isolation API Specification

Problem is, this JSR is going nowhere. There are some big corps onboard, but no one seem's interested in defining a common API. Sun's management is clearly not interested (more precisely, "Sun's managment has decided not to commit any resources to this project in the short term.") So there are lots of research papers, prototypes and Master's thesis, which are all very interesting, but no working implementation that everyone can use.

That's really sucks because with an implementation of this JSR, the JVM could get a lot more OS-like. Too bad.