Hi,
thanks for experimenting with Nashorn!
As far as your example is concerned, Nashorn is not thread safe by design.
Indeed, if you evaluate
new NashornScriptEngineFactory().getParameter("THREADING")
it'll return null, which means "the engine implementation is not thread safe,
and cannot be used to execute scripts concurrently on multiple threads" -- see
<http://docs.oracle.com/javase/7/docs/api/javax/script/ScriptEngineFactory.html#getParameter(java.lang.String)>
Nashorn library internals themselves are thread safe to the degree that we're
using synchronized and concurrent data structures for various internal static
caches et cetera, but JavaScript programs executing within a single engine
instance are not thread safe.
As I said, this is by design. ECMAScript 5.1 language specification doesn't
define multithreading semantics for programs written in the language; they are
inherently single threaded. If we were to make them thread safe, we'd be
sacrificing single threaded performance for a behavior that falls outside of
the specification. You can always create one script engine per thread using the
same factory - that should work in a multithreaded scenario.
Actually, in your above example, since the JavaScript program has no explicit
guarding of concurrent access to variable `i` you seem like you would actually
even expect to have an engine that has "THREAD-ISOLATED" as its threading model
instead of the simpler "MULTITHREADED" - that' very rare in an engine, usually
hard to implement efficiently (do you clone all of the data up front? do you
implement a copy-on-write semantics?) , and is functionally simpler to just
have a non-threadsafe engine and let the users manage their own thread
isolation by creating one engine instance per thread.
Cheers,
Attila.
On Jul 9, 2013, at 10:01 AM, Tobias Schlottke <[email protected]>
wrote:
>
> Hi there,
>
> we're currently planning to switch our infrastructure from Rhino to Nashorn
> but are experiencing some threading Issues that nobody addressed so far.
> I tweeted with Jim Laskey and he kindly asked me to post it to this list.
>
> Example:
>
> https://gist.github.com/tobsch/5955518
>
> Could could you check this example and check if this really is a problem in
> your eyes or if it is supposed to be this way?
>
> Best,
>
> Tobias
>
