Use multiprocessing.managers for the Python runner

1 files changed, 77 insertions, 55 deletions

diff --git a/python/runner/main.py b/python/runner/main.py
index b9233cd..4e1af53 100755
--- a/python/runner/main.py
+++ b/python/runner/main.py
@@ -1,18 +1,23 @@
 #!/usr/bin/python3
 
-from http.server import BaseHTTPRequestHandler, HTTPServer
-from socketserver import ForkingMixIn
-
+from fcntl import fcntl, F_GETFL, F_SETFL
 import io
-import json
 import multiprocessing
+import multiprocessing.managers
+import os
+import subprocess
 import sys
+import threading
 import time
+import uuid
+
+interpreters = {}
+module_access_lock = threading.Lock()
 
 # Execute [code] and evaluate [expr]. Input is given by the string [stdin].
 # Return result of evaluation, the contents of stdout and stderr, and the
 # exception traceback.
-def run_exec(conn, code, expr=None, stdin=''):
+def _run_exec(conn, code, expr=None, stdin=''):
     result, out, err, exc = None, None, None, None
     sys.stdin = io.StringIO(stdin)
     sys.stdout = io.StringIO()
@@ -35,61 +40,78 @@ def run_exec(conn, code, expr=None, stdin=''):
         sys.stderr.close()
         conn.send((result, out, err, exc))
 
-# Call run_exec in a separate process for each input and return a list of
-# results from those calls. If a call times out, 'timed out' is returned in
-# place of exception traceback.
-def run(code, inputs, timeout):
-    # Launch processes.
-    futures = []
-    for expr, stdin in inputs:
-        conn_parent, conn_child = multiprocessing.Pipe()
-        p = multiprocessing.Process(target=run_exec, args=(conn_child, code, expr, stdin))
-        p.start()
-        futures.append((p, conn_parent))
+class Python(object):
+    # Call run_exec in a separate process for each input and return a list of
+    # results from those calls. If a call times out, 'timed out' is returned in
+    # place of exception traceback.
+    def run(self, code, inputs, timeout):
+        # Launch processes.
+        futures = []
+        for expr, stdin in inputs:
+            conn_parent, conn_child = multiprocessing.Pipe()
+            p = multiprocessing.Process(target=_run_exec, args=(conn_child, code, expr, stdin))
+            p.start()
+            futures.append((p, conn_parent))
 
-    # Wait for results.
-    results = []
-    start = time.monotonic()
-    for p, conn in futures:
-        now = time.monotonic()
-        real_timeout = max(0, timeout - (now - start))
-        if conn.poll(real_timeout):
-            results.append(conn.recv())
-        else:
-            results.append('timed out')
-        p.terminate()
+        # Wait for results.
+        results = []
+        start = time.monotonic()
+        for p, conn in futures:
+            now = time.monotonic()
+            real_timeout = max(0, timeout - (now - start))
+            if conn.poll(real_timeout):
+                results.append(conn.recv())
+            else:
+                results.append('timed out')
+            p.terminate()
+        return results
 
-    return results
+    # Start and return a new Python interpreter process.
+    def create(self):
+        directory = os.path.dirname(os.path.realpath(__file__))
+        script = os.path.join(directory, 'interpreter.py')
+        p = subprocess.Popen([script],
+                stdin=subprocess.PIPE,
+                stdout=subprocess.PIPE,
+                stderr=subprocess.STDOUT)
+        # Set the non-blocking flag for stdout.
+        flags = fcntl(p.stdout, F_GETFL)
+        fcntl(p.stdout, F_SETFL, flags | os.O_NONBLOCK)
 
-class RequestHandler(BaseHTTPRequestHandler):
-    def do_OPTIONS(self):
-        self.send_response(200)
-        self.end_headers()
+        interpreter_id = uuid.uuid4().hex
+        with module_access_lock:
+            interpreters[interpreter_id] = p
+        return interpreter_id
 
-    def do_GET(self):
-        reply = {'status': 'error'}
-        if self.path == '/run':
-            length = int(self.headers.get('Content-Length', 0))
-            text = self.rfile.read(length)
-            request = json.loads(text.decode('utf-8'))
-            results = run(request.get('code', ''),
-                          request.get('inputs', []),
-                          request.get('timeout', 1.0))
-            reply = {'status': 'ok', 'results': results}
+    # Read any available bytes from the interpreter's stdout.
+    def pull(self, interpreter_id):
+        with module_access_lock:
+            interpreter = interpreters[interpreter_id]
+        stdout = interpreter.stdout.read()
+        if stdout:
+            stdout = stdout.decode('utf-8')
+        return stdout
 
-        reply_text = json.dumps(reply).encode('utf-8')
-        self.send_response(200)
-        self.send_header('Content-Length', len(reply_text))
-        self.end_headers()
-        self.wfile.write(reply_text)
+    # Push a string to the interpreter's stdin.
+    def push(self, interpreter_id, stdin):
+        with module_access_lock:
+            interpreter = interpreters[interpreter_id]
+        interpreter.stdin.write(stdin.encode('utf-8'))
+        interpreter.stdin.flush()
 
-class ForkingHTTPServer(ForkingMixIn, HTTPServer):
+    # Kill an interpreter process.
+    def destroy(self, interpreter_id):
+        with module_access_lock:
+            interpreter = interpreters[interpreter_id]
+            del interpreters[interpreter_id]
+        interpreter.kill()
+
+class PythonManager(multiprocessing.managers.BaseManager):
     pass
 
-server = ForkingHTTPServer(('localhost', 3031), RequestHandler)
-print('Python engine started.')
-try:
-    server.serve_forever()
-except KeyboardInterrupt:
-    print('Keyboard interrupt received, exiting.')
-    server.server_close()
+PythonManager.register('Python', callable=Python)
+
+if __name__ == '__main__':
+    print('Python engine started.')
+    m = PythonManager(address=('localhost', 3031), authkey=b'c0d3q3y-python')
+    m.get_server().serve_forever()