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diff mercurial/wireprotoframing.py @ 40026:b099e6032f38

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wireprotov2: server support for sending content redirects A "content redirect" can be sent in place of inline response content. In terms of code, we model a content redirect as a special type of response object holding the attributes describing that redirect. Sending a content redirect thus becomes as simple as the object emission layer sending an instance of that type. A cacher using externally-addressable content storage could replace the outgoing object stream with an object advertising its location. The bulk of the code in this commit is teaching the output layer which handles the object stream to recognize alternate location objects. The rules are that if an alternate location object is present, it must be the first and only object in the object stream. Otherwise the server emits an error. Differential Revision: https://phab.mercurial-scm.org/D4777
author Gregory Szorc <gregory.szorc@gmail.com>
date Wed, 26 Sep 2018 18:07:55 -0700
parents 86b22a4cfab1
children e2fe1074024c
line wrap: on
line diff
--- a/mercurial/wireprotoframing.py	Wed Sep 26 15:02:19 2018 -0700
+++ b/mercurial/wireprotoframing.py	Wed Sep 26 18:07:55 2018 -0700
@@ -21,6 +21,7 @@
 from . import (
     encoding,
     error,
+    pycompat,
     util,
     wireprototypes,
 )
@@ -429,6 +430,26 @@
                             flags=FLAG_COMMAND_RESPONSE_EOS,
                             payload=b'')
 
+def createalternatelocationresponseframe(stream, requestid, location):
+    data = {
+        b'status': b'redirect',
+        b'location': {
+            b'url': location.url,
+            b'mediatype': location.mediatype,
+        }
+    }
+
+    for a in (r'size', r'fullhashes', r'fullhashseed', r'serverdercerts',
+              r'servercadercerts'):
+        value = getattr(location, a)
+        if value is not None:
+            data[b'location'][pycompat.bytestr(a)] = value
+
+    return stream.makeframe(requestid=requestid,
+                            typeid=FRAME_TYPE_COMMAND_RESPONSE,
+                            flags=FLAG_COMMAND_RESPONSE_CONTINUATION,
+                            payload=b''.join(cborutil.streamencode(data)))
+
 def createcommanderrorresponse(stream, requestid, message, args=None):
     # TODO should this be using a list of {'msg': ..., 'args': {}} so atom
     # formatting works consistently?
@@ -813,6 +834,7 @@
 
         def sendframes():
             emitted = False
+            alternatelocationsent = False
             emitter = bufferingcommandresponseemitter(stream, requestid)
             while True:
                 try:
@@ -841,6 +863,25 @@
                     break
 
                 try:
+                    # Alternate location responses can only be the first and
+                    # only object in the output stream.
+                    if isinstance(o, wireprototypes.alternatelocationresponse):
+                        if emitted:
+                            raise error.ProgrammingError(
+                                'alternatelocationresponse seen after initial '
+                                'output object')
+
+                        yield createalternatelocationresponseframe(
+                            stream, requestid, o)
+
+                        alternatelocationsent = True
+                        emitted = True
+                        continue
+
+                    if alternatelocationsent:
+                        raise error.ProgrammingError(
+                            'object follows alternatelocationresponse')
+
                     if not emitted:
                         yield createcommandresponseokframe(stream, requestid)
                         emitted = True
@@ -977,6 +1018,7 @@
             'requestid': requestid,
             'command': request[b'name'],
             'args': request[b'args'],
+            'redirect': request.get(b'redirect'),
             'data': entry['data'].getvalue() if entry['data'] else None,
         }