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diff mercurial/wireprotoserver.py @ 37059:861e9d37e56e

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wireproto: buffer output frames when in half duplex mode Previously, when told that a response was ready, the server reactor would instruct the caller to send frames immediately. This was OK as an initial implementation. But it would not work for half-duplex connections where the sender can't receive until all data has been transmitted - such as httplib based clients. In this commit, we teach the reactor that output frames should be buffered until end of input is seen. This required a new event to inform the reactor of end of input. The result from that event will instruct the consumer to send all buffered frames. The HTTP server is buffered by default. This change effectively hides the complexity of buffering within the reactor so that transports need not be concerned about it. This helps keep the transports "dumb" and will make implementing multiple requests-responses per atomic exchange (like an HTTP request) much simpler. Differential Revision: https://phab.mercurial-scm.org/D2860
author Gregory Szorc <gregory.szorc@gmail.com>
date Wed, 14 Mar 2018 14:01:16 -0700
parents 61393f888dfe
children 2ec1fb9de638
line wrap: on
line diff
--- a/mercurial/wireprotoserver.py	Wed Mar 14 13:57:52 2018 -0700
+++ b/mercurial/wireprotoserver.py	Wed Mar 14 14:01:16 2018 -0700
@@ -401,6 +401,10 @@
         states.append(json.dumps((action, meta), sort_keys=True,
                                  separators=(', ', ': ')))
 
+    action, meta = reactor.oninputeof()
+    meta['action'] = action
+    states.append(json.dumps(meta, sort_keys=True, separators=(', ',': ')))
+
     res.status = b'200 OK'
     res.headers[b'Content-Type'] = b'text/plain'
     res.setbodybytes(b'\n'.join(states))
@@ -411,7 +415,10 @@
     Called when the HTTP request contains unified frame-based protocol
     frames for evaluation.
     """
-    reactor = wireprotoframing.serverreactor()
+    # TODO Some HTTP clients are full duplex and can receive data before
+    # the entire request is transmitted. Figure out a way to indicate support
+    # for that so we can opt into full duplex mode.
+    reactor = wireprotoframing.serverreactor(deferoutput=True)
     seencommand = False
 
     while True:
@@ -448,6 +455,19 @@
             raise error.ProgrammingError(
                 'unhandled action from frame processor: %s' % action)
 
+    action, meta = reactor.oninputeof()
+    if action == 'sendframes':
+        # We assume we haven't started sending the response yet. If we're
+        # wrong, the response type will raise an exception.
+        res.status = b'200 OK'
+        res.headers[b'Content-Type'] = FRAMINGTYPE
+        res.setbodygen(meta['framegen'])
+    elif action == 'noop':
+        pass
+    else:
+        raise error.ProgrammingError('unhandled action from frame processor: %s'
+                                     % action)
+
 def _httpv2runcommand(ui, repo, req, res, authedperm, reqcommand, reactor,
                       command):
     """Dispatch a wire protocol command made from HTTPv2 requests.
@@ -504,6 +524,8 @@
 
     if action == 'sendframes':
         res.setbodygen(meta['framegen'])
+    elif action == 'noop':
+        pass
     else:
         raise error.ProgrammingError('unhandled event from reactor: %s' %
                                      action)