davsclaus commented on code in PR #26311:
URL: https://github.com/apache/camel/pull/26311#discussion_r3989772222
##########
components/camel-python/src/main/java/org/apache/camel/language/python/PythonLanguage.java:
##########
@@ -75,19 +75,22 @@ public <T> T evaluate(String script, Map<String, Object>
bindings, Class<T> resu
}
}
- try {
- if (bindings != null) {
- bindings.forEach(compiler::set);
- }
- PyObject out = compiler.eval(code);
- if (out != null) {
- String value = out.toString();
- return
getCamelContext().getTypeConverter().convertTo(resultType, value);
+ // the interpreter is shared by every caller of this method: bind, run
and clean up under one lock
+ synchronized (compiler) {
Review Comment:
**The compile a few lines above this is on the same shared interpreter, but
outside the lock.**
`PythonInterpreter.compile(Reader, String)` is not a pure function of its
argument — it reads `this.cflags`, passes that same mutable `CompilerFlags`
instance into `ParserFacade.parseExpressionOrModule(...)` (which writes back
any `from __future__` flags it finds), and then calls `setSystemState()`, which
installs this interpreter's `PySystemState` as the *thread's* current one.
So two threads missing the cache on different scripts mutate one
`CompilerFlags`, and a compiling thread races the `setSystemState()`/`eval` of
a thread already inside this `synchronized` block. Same
shared-mutable-interpreter race the PR fixes on the evaluation path, just on
the compile path.
Pulling the cache miss inside the lock closes it and also makes the
double-checked lookup honest:
```java
synchronized (compiler) {
PyCode code = getCompiledScriptFromCache(script);
if (code == null) {
try {
code = compiler.compile(script);
addCompiledScriptToCache(script, code);
} catch (Exception e) {
throw new ExpressionIllegalSyntaxException(script, e);
}
}
try {
...
```
(`PythonExpression`'s constructor compiles against its own private
interpreter before the expression is published, so that one is fine as-is.)
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