Improve error handling (#433)

python/sglang/lang/interpreter.py

@@ -29,7 +29,7 @@ from sglang.lang.ir import (
     SglVarScopeBegin,
     SglVarScopeEnd,
 )
-from sglang.utils import encode_image_base64
+from sglang.utils import encode_image_base64, get_exception_traceback
 
 
 def run_internal(state, program, func_args, func_kwargs, sync):
@@ -195,6 +195,7 @@ class StreamExecutor:
         self.variable_event = {}  # Dict[name: str -> event: threading.Event]
         self.meta_info = {}  # Dict[name: str -> info: str]
         self.is_finished = False
+        self.error = None
 
         # For completion
         self.text_ = ""  # The full text
@@ -310,17 +311,39 @@ class StreamExecutor:
         self.backend.end_program(self)
 
     def _thread_worker_func(self):
+        error = None
+
         while True:
             expr = self.queue.get()
             if expr is None:
                 self.queue.task_done()
                 break
 
-            self._execute(expr)
+            try:
+                self._execute(expr)
+            except Exception as e:
+                print(f"Error in stream_executor: {get_exception_traceback()}")
+                error = e
+                break
             self.queue.task_done()
             if self.stream_text_event:
                 self.stream_text_event.set()
 
+        # Clean the queue and events
+        if error is not None:
+            try:
+                while True:
+                    self.queue.task_done()
+                    self.queue.get_nowait()
+            except queue.Empty:
+                pass
+            for name in self.variable_event:
+                self.variable_event[name].set()
+            if self.stream_var_event:
+                for name in self.stream_var_event:
+                    self.stream_var_event[name].set()
+            self.error = error
+
         if self.stream_text_event:
             self.stream_text_event.set()
 
@@ -679,7 +702,9 @@ class ProgramState:
         return self.stream_executor.messages()
 
     def sync(self):
-        return self.stream_executor.sync()
+        ret = self.stream_executor.sync()
+        self.error = self.stream_executor.error
+        return ret
 
     def text_iter(self, var_name: Optional[str] = None):
         if self.stream_executor.stream:
@@ -769,6 +794,9 @@ class ProgramState:
     def __setitem__(self, name, value):
         self.set_var(name, value)
 
+    def __contains__(self, name):
+        return name in self.stream_executor.variables
+
     def __del__(self):
         self.stream_executor.end()