1 files changed, 18 insertions, 1 deletions
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index 86341cc4cc..c20de57991 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -23,6 +23,7 @@ from synapse.util.stringutils import random_string
from synapse.util.caches.expiringcache import ExpiringCache
from synapse.http.client import SpiderHttpClient
from synapse.http.server import request_handler, respond_with_json, respond_with_json_bytes
+from synapse.util.async import ObservableDeferred
import os
import re
@@ -46,6 +47,8 @@ class PreviewUrlResource(BaseMediaResource):
)
self.cache.start()
+ self.downloads = {}
+
def render_GET(self, request):
self._async_render_GET(request)
return NOT_DONE_YET
@@ -86,7 +89,21 @@ class PreviewUrlResource(BaseMediaResource):
)
return
- media_info = yield self._download_url(url, requester.user)
+ # Ensure only one download for a given URL is active at a time
+ download = self.downloads.get(url)
+ if download is None:
+ download = self._download_url(url, requester.user)
+ download = ObservableDeferred(
+ download,
+ consumeErrors=True
+ )
+ self.downloads[url] = download
+
+ @download.addBoth
+ def callback(media_info):
+ del self.downloads[key]
+ return media_info
+ media_info = yield download.observe()
# FIXME: we should probably update our cache now anyway, so that
# even if the OG calculation raises, we don't keep hammering on the
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