[bug] raise u1db errors based on http response

When we started to use the twisted http agent, we forgot to intercept http
response and raise the appropriate u1db errors based on the response status
code and messages. This commit implements that by redefining the http body
reader used by the http agent.

1 files changed, 109 insertions, 1 deletions

diff --git a/client/src/leap/soledad/client/http_target.py b/client/src/leap/soledad/client/http_target.py
index 19ebd82f..ca901633 100644
--- a/client/src/leap/soledad/client/http_target.py
+++ b/client/src/leap/soledad/client/http_target.py
@@ -25,15 +25,21 @@ after receiving.
 import json
 import base64
 import logging
+import warnings
 
 from uuid import uuid4
 
 from twisted.internet import defer
 from twisted.web.error import Error
+from twisted.web.client import _ReadBodyProtocol
+from twisted.web.client import PartialDownloadError
+from twisted.web._newclient import ResponseDone
+from twisted.web._newclient import PotentialDataLoss
 
 from u1db import errors
 from u1db import SyncTarget
 from u1db.remote import utils
+from u1db.remote import http_errors
 
 from leap.common.http import HTTPClient
 
@@ -50,6 +56,108 @@ from leap.soledad.client.encdecpool import SyncDecrypterPool
 logger = logging.getLogger(__name__)
 
 
+# we want to make sure that HTTP errors will raise appropriate u1db errors,
+# that is, fire errbacks with the appropriate failures, in the context of
+# twisted. Because of that, we redefine the http body reader used by the HTTP
+# client below.
+
+class ReadBodyProtocol(_ReadBodyProtocol):
+
+    def __init__(self, response, deferred):
+        """
+        Initialize the protocol, additionally storing the response headers.
+        """
+        _ReadBodyProtocol.__init__(
+            self, response.code, response.phrase, deferred)
+        self.headers = response.headers
+
+    # ---8<--- snippet from u1db.remote.http_client, modified to use errbacks
+    def _error(self, respdic):
+        descr = respdic.get("error")
+        exc_cls = errors.wire_description_to_exc.get(descr)
+        if exc_cls is not None:
+            message = respdic.get("message")
+            self.deferred.errback(exc_cls(message))
+    # ---8<--- end of snippet from u1db.remote.http_client
+
+    def connectionLost(self, reason):
+        """
+        Deliver the accumulated response bytes to the waiting L{Deferred}, if
+        the response body has been completely received without error.
+        """
+        if reason.check(ResponseDone):
+
+            body = b''.join(self.dataBuffer)
+
+            # ---8<--- snippet from u1db.remote.http_client
+            if self.status in (200, 201):
+                self.deferred.callback(body)
+            elif self.status in http_errors.ERROR_STATUSES:
+                try:
+                    respdic = json.loads(body)
+                except ValueError:
+                    self.deferred.errback(
+                        errors.HTTPError(self.status, body, self.headers))
+                else:
+                    self._error(respdic)
+            # special cases
+            elif self.status == 503:
+                self.deferred.errback(errors.Unavailable(body, self.headers))
+            else:
+                self.deferred.errback(
+                    errors.HTTPError(self.status, body, self.headers))
+            # ---8<--- end of snippet from u1db.remote.http_client
+
+        elif reason.check(PotentialDataLoss):
+            self.deferred.errback(
+                PartialDownloadError(self.status, self.message,
+                                     b''.join(self.dataBuffer)))
+        else:
+            self.deferred.errback(reason)
+
+
+def readBody(response):
+    """
+    Get the body of an L{IResponse} and return it as a byte string.
+
+    This is a helper function for clients that don't want to incrementally
+    receive the body of an HTTP response.
+
+    @param response: The HTTP response for which the body will be read.
+    @type response: L{IResponse} provider
+
+    @return: A L{Deferred} which will fire with the body of the response.
+        Cancelling it will close the connection to the server immediately.
+    """
+    def cancel(deferred):
+        """
+        Cancel a L{readBody} call, close the connection to the HTTP server
+        immediately, if it is still open.
+
+        @param deferred: The cancelled L{defer.Deferred}.
+        """
+        abort = getAbort()
+        if abort is not None:
+            abort()
+
+    d = defer.Deferred(cancel)
+    protocol = ReadBodyProtocol(response, d)
+
+    def getAbort():
+        return getattr(protocol.transport, 'abortConnection', None)
+
+    response.deliverBody(protocol)
+
+    if protocol.transport is not None and getAbort() is None:
+        warnings.warn(
+            'Using readBody with a transport that does not have an '
+            'abortConnection method',
+            category=DeprecationWarning,
+            stacklevel=2)
+
+    return d
+
+
 class SoledadHTTPSyncTarget(SyncTarget):
 
     """
@@ -576,7 +684,7 @@ class SoledadHTTPSyncTarget(SyncTarget):
                 source_replica_uid=self.source_replica_uid)
 
     def _http_request(self, url, method='GET', body=None, headers={}):
-        d = self._http.request(url, method, body, headers)
+        d = self._http.request(url, method, body, headers, readBody)
         d.addErrback(_unauth_to_invalid_token_error)
         return d