diff options
Diffstat (limited to '')
| -rw-r--r-- | synapse/rest/media/v1/preview_url_resource.py | 88 |
1 files changed, 47 insertions, 41 deletions
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py index 7907a9d17a..723f7043f4 100644 --- a/synapse/rest/media/v1/preview_url_resource.py +++ b/synapse/rest/media/v1/preview_url_resource.py @@ -20,6 +20,7 @@ from twisted.web.resource import Resource from synapse.api.errors import ( SynapseError, Codes, ) +from synapse.util.logcontext import preserve_fn, make_deferred_yieldable from synapse.util.stringutils import random_string from synapse.util.caches.expiringcache import ExpiringCache from synapse.http.client import SpiderHttpClient @@ -63,16 +64,15 @@ class PreviewUrlResource(Resource): self.url_preview_url_blacklist = hs.config.url_preview_url_blacklist - # simple memory cache mapping urls to OG metadata - self.cache = ExpiringCache( + # memory cache mapping urls to an ObservableDeferred returning + # JSON-encoded OG metadata + self._cache = ExpiringCache( cache_name="url_previews", clock=self.clock, # don't spider URLs more often than once an hour expiry_ms=60 * 60 * 1000, ) - self.cache.start() - - self.downloads = {} + self._cache.start() self._cleaner_loop = self.clock.looping_call( self._expire_url_cache_data, 10 * 1000 @@ -94,6 +94,7 @@ class PreviewUrlResource(Resource): else: ts = self.clock.time_msec() + # XXX: we could move this into _do_preview if we wanted. url_tuple = urlparse.urlsplit(url) for entry in self.url_preview_url_blacklist: match = True @@ -126,14 +127,42 @@ class PreviewUrlResource(Resource): Codes.UNKNOWN ) - # first check the memory cache - good to handle all the clients on this - # HS thundering away to preview the same URL at the same time. - og = self.cache.get(url) - if og: - respond_with_json_bytes(request, 200, json.dumps(og), send_cors=True) - return + # the in-memory cache: + # * ensures that only one request is active at a time + # * takes load off the DB for the thundering herds + # * also caches any failures (unlike the DB) so we don't keep + # requesting the same endpoint + + observable = self._cache.get(url) + + if not observable: + download = preserve_fn(self._do_preview)( + url, requester.user, ts, + ) + observable = ObservableDeferred( + download, + consumeErrors=True + ) + self._cache[url] = observable + else: + logger.info("Returning cached response") + + og = yield make_deferred_yieldable(observable.observe()) + respond_with_json_bytes(request, 200, og, send_cors=True) - # then check the URL cache in the DB (which will also provide us with + @defer.inlineCallbacks + def _do_preview(self, url, user, ts): + """Check the db, and download the URL and build a preview + + Args: + url (str): + user (str): + ts (int): + + Returns: + Deferred[str]: json-encoded og data + """ + # check the URL cache in the DB (which will also provide us with # historical previews, if we have any) cache_result = yield self.store.get_url_cache(url, ts) if ( @@ -141,32 +170,10 @@ class PreviewUrlResource(Resource): cache_result["expires_ts"] > ts and cache_result["response_code"] / 100 == 2 ): - respond_with_json_bytes( - request, 200, cache_result["og"].encode('utf-8'), - send_cors=True - ) + defer.returnValue(cache_result["og"]) return - # 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[url] - 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 - # remote server. For now, leave it uncached to aid debugging OG - # calculation problems + media_info = yield self._download_url(url, user) logger.debug("got media_info of '%s'" % media_info) @@ -212,7 +219,7 @@ class PreviewUrlResource(Resource): # just rely on the caching on the master request to speed things up. if 'og:image' in og and og['og:image']: image_info = yield self._download_url( - _rebase_url(og['og:image'], media_info['uri']), requester.user + _rebase_url(og['og:image'], media_info['uri']), user ) if _is_media(image_info['media_type']): @@ -239,8 +246,7 @@ class PreviewUrlResource(Resource): logger.debug("Calculated OG for %s as %s" % (url, og)) - # store OG in ephemeral in-memory cache - self.cache[url] = og + jsonog = json.dumps(og) # store OG in history-aware DB cache yield self.store.store_url_cache( @@ -248,12 +254,12 @@ class PreviewUrlResource(Resource): media_info["response_code"], media_info["etag"], media_info["expires"] + media_info["created_ts"], - json.dumps(og), + jsonog, media_info["filesystem_id"], media_info["created_ts"], ) - respond_with_json_bytes(request, 200, json.dumps(og), send_cors=True) + defer.returnValue(jsonog) @defer.inlineCallbacks def _download_url(self, url, user): |