Just for reference...this seems to be
https://stackoverflow.com/questions/45578426/lock-contention-in-groovy-shell-interpreter-under-high-load
more inline
On 09.08.2017 18:58, Aman Jain wrote:
Hello,
We are evaluating GroovyShell
<http://groovy-lang.org/download.html> interpreter (v2.4) in our
application for dynamically executing standard Java syntax.
Earlier, we were using Java BeanShell Interpreter for it, but it has an
issue
<https://stackoverflow.com/questions/45450947/lock-contention-in-java-beanshell-interpreter-under-high-load/45451768#45451768> under
high load which prompted us to look for an alternative such as Groovy.
We are seeing thread lock contention when multiple threads execute the
below sample code simultaneously. We have multiple threads in the
blocked state which is degrading application performance.
I am missing the counter part, the one that owns the lock. but looking at
java.lang.Thread.State: BLOCKED (on object monitor)
at java.lang.ClassLoader.loadClass(ClassLoader.java:404)
- waiting to lock <0x00000007bc425e40> (a java.lang.Object)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
at java.lang.ClassLoader.loadClass(ClassLoader.java:411)
my strong assumption would be, that the counter part is also in
java.lang.ClassLoader. My guess would be, that we are currently trying
to load a class, probably from some other thread. If you have code like
static String script = "int y = x * x; System.out.println(\"** value of y ** :: \" +
y ); ";
GroovyShell gs = new GroovyShell();
Script evalScript = gs.parse("void evalMethod() {" + script + "}");
// bind variables
Binding binding = new Binding();
binding.setVariable("x", 5);
evalScript.setBinding(binding);
// invoke eval method
evalScript.invokeMethod("evalMethod", null);
you would with each thread execution do a new compilation, which is
where the majority of those class look-ups is coming from. The script
form example contains System, which will be looked-up in maybe 10
variants before the compiler is happy. That makes 9 false look-ups.
Multiply this with a hundred threads and you get 900 look-ups for
classes, that actually do not exist. So the goal would be reuse. My
suggestion would be then:
for all threads:
static String script = "int y = x * x; System.out.println(\"** value of y ** :: \" +
y ); ";
GroovyShell gs = new GroovyShell();
Script evalScript = gs.parse("void evalMethod() {" + script + "}");
in each thread:
// bind variables
Binding binding = new Binding();
binding.setVariable("x", 5);
Script threadEvalScript =
InvokerHelper.createScript(evalScript.getClas(), binding);
// invoke eval method
threadEvalScript.invokeMethod("evalMethod", null);
Even better would be of course to make a pool of script instances and
use them from there
My questions are:
1. Has anyone experienced such problem? If yes, can you please suggest
any possible resolution for it? I googled around for this problem
and few blogs suggested to cache groovy |Script| object. Is
|Script| object thread-safe? Moreover, I need to bind variables to
|Script|object (via groovy |Binding| object, which is different for
each execution in different threads), so I don't think caching
groovy |Script| object is a viable option.
You have to understand that there is the script and the binding. Ideally
the script itself stores all the state in the binding. Then you need one
combination of script and binding per thread that is concurrently
running. How you can do that I tried to show above already a bit.
btw, Binding is not thread-safe, but nothing prevents you from
implementing your own Binding, that is. But given your statement, that
the Binding is different each time I do not think there is a problem
with this.
2. Are there any best practices that I need to follow while using
Groovy Shell interpreter with Java?
Biggest problem normally is the delayed clean-up of the generated
classes and meta classes, but this should not concern you here, once you
managed to reuse the script class.
bye Jochen
