nashorn CompiledScript graalvm equivalent

I have a fairly big file that needs to often be evaluated,

with nashorn I used to do something like that :

CompiledScript compiledScript = ((Compilable) engine).compile(text);

and later on, I could call many times the following :

Context context = new SimpleScriptContext();
compiledScript.eval(context);

this was quite fast.

Using the new Polyglot API, I do :

Source source = Source.newBuilder("js", myFile).build();

then :

Context context = Context.newBuilder("js").option("js.nashorn-compat", "true").build();
context.eval(source)

Using jmh, I have a big performance difference between the two

Benchmark                     Mode  Cnt   Score    Error  Units
JmhBenchmark.testEvalGraal    avgt    5  42,855 ± 11,118  ms/op
JmhBenchmark.testEvalNashorn  avgt    5   2,739 ±  1,101  ms/op

If I do the eval on the same context, it is working properly, but I don't want to have a shared context between two consecutive eval (unless the concept of Context of Graal is not the same as the one from Nashorn).

Solution

To reproduce your ScriptEngine setup with GraalVM, you should re-use the same Engine (org.graalvm.polyglot.Engine) and .close() the context after use:

Source source = Source.newBuilder("js", myFile).build();
Engine engine = Engine.create();

and later:

Context context = Context.newBuilder("js")
                         .engine(engine)
                         .option("js.nashorn-compat", "true").build();
context.eval(source);
context.close();

Quoting the Context.Builder.engine documentation:

Explicitly sets the underlying engine to use. By default, every context has its own isolated engine. If multiple contexts are created from one engine, then they may share/cache certain system resources like ASTs or optimized code by specifying a single underlying engine.