Finally figured out twisted concurrency

examples/counter.py

@@ -0,0 +1,45 @@
+"""
+An endpoint that streams incrementing numbers forever.
+
+This is an example of how a jetforce application can respond with a generator
+function instead of plain text/bytes. The server will iterate over the
+generator and write the data to the socket in-between each iteration. This can
+be useful if you want to serve a large response, like a binary file, without
+loading the entire response into memory at once.
+
+The server will schedule your application code to be run inside of a separate
+thread, using twisted's built-in thread pool. So even though the counter
+function contains a sleep(), it will not block the server from handling other
+requests. Try requesting this endpoint over two connections simultaneously.
+
+> jetforce-client gemini://localhost
+> jetforce-client gemini://localhost
+"""
+
+import time
+
+from jetforce import GeminiServer, JetforceApplication, Response, Status
+
+
+def counter():
+    """
+    Generator function that counts to ∞.
+    """
+    x = 0
+    while True:
+        time.sleep(1)
+        x += 1
+        yield f"{x}\r\n"
+
+
+app = JetforceApplication()
+
+
+@app.route()
+def index(request):
+    return Response(Status.SUCCESS, "text/plain", counter())
+
+
+if __name__ == "__main__":
+    server = GeminiServer(app)
+    server.run()

jetforce/protocol.py

@@ -5,7 +5,8 @@ import typing
 import urllib.parse
 
 from twisted.internet.address import IPv4Address, IPv6Address
-from twisted.internet.defer import inlineCallbacks
+from twisted.internet.defer import ensureDeferred
+from twisted.internet.threads import deferToThread
 from twisted.protocols.basic import LineOnlyReceiver
 
 from .__version__ import __version__
@@ -64,10 +65,10 @@ class GeminiProtocol(LineOnlyReceiver):
         connection without managing any state.
         """
         self.request = line
-        return self._handle_request_noblock()
+        return ensureDeferred(self._handle_request_noblock())
+
+    async def _handle_request_noblock(self):
 
-    @inlineCallbacks
-    def _handle_request_noblock(self):
         try:
             self.parse_header()
         except Exception:
@@ -79,9 +80,15 @@ class GeminiProtocol(LineOnlyReceiver):
 
         try:
             environ = self.build_environ()
-            for data in self.app(environ, self.write_status):
-                self.write_body(data)
-                yield  # Yield control to the event loop
+            response_generator = await deferToThread(
+                self.app, environ, self.write_status
+            )
+            while True:
+                try:
+                    data = await deferToThread(response_generator.__next__)
+                    self.write_body(data)
+                except StopIteration:
+                    break
         except Exception:
             self.write_status(Status.CGI_ERROR, "An unexpected error occurred")
         finally:
@@ -163,16 +170,14 @@ class GeminiProtocol(LineOnlyReceiver):
         self.meta = meta
         self.response_buffer = f"{status}\t{meta}\r\n"
 
-    def write_body(self, data: typing.Union[str, bytes, None]) -> None:
+    def write_body(self, data: typing.Union[str, bytes]) -> None:
         """
         Write bytes to the gemini response body.
         """
-        if data is None:
-            return
-
-        self.flush_status()
         if isinstance(data, str):
             data = data.encode()
+
+        self.flush_status()
         self.response_size += len(data)
         self.transport.write(data)
 

jetforce_client.py

@@ -7,6 +7,7 @@ A dead-simple gemini client intended to be used for server development and testi
 import argparse
 import socket
 import ssl
+import sys
 import urllib.parse
 
 context = ssl.create_default_context()
@@ -25,11 +26,11 @@ def fetch(url: str, host: str = None, port: str = None):
     with socket.create_connection((host, port)) as sock:
         with context.wrap_socket(sock) as ssock:
             ssock.sendall((url + "\r\n").encode())
-            fp = ssock.makefile("rb")
-            header = fp.readline().decode()
-            print(header)
-            body = fp.read().decode()
-            print(body)
+            fp = ssock.makefile("rb", buffering=0)
+            data = fp.read(1024)
+            while data:
+                sys.stdout.buffer.write(data)
+                data = fp.read(1024)
 
 
 def run_client():