diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index 317d333b12..f108da05db 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -22,9 +22,11 @@ import re
import shutil
import sys
import traceback
-from typing import TYPE_CHECKING, Any, Dict, Generator, Iterable, Optional, Union
+from typing import TYPE_CHECKING, Dict, Generator, Iterable, Optional, Union
from urllib import parse as urlparse
+import attr
+
from twisted.internet.error import DNSLookupError
from twisted.web.server import Request
@@ -42,6 +44,7 @@ from synapse.metrics.background_process_metrics import run_as_background_process
from synapse.rest.media.v1._base import get_filename_from_headers
from synapse.rest.media.v1.media_storage import MediaStorage
from synapse.rest.media.v1.oembed import OEmbedError, OEmbedProvider
+from synapse.types import JsonDict
from synapse.util import json_encoder
from synapse.util.async_helpers import ObservableDeferred
from synapse.util.caches.expiringcache import ExpiringCache
@@ -71,7 +74,43 @@ OG_TAG_VALUE_MAXLEN = 1000
ONE_HOUR = 60 * 60 * 1000
+@attr.s(slots=True, frozen=True, auto_attribs=True)
+class MediaInfo:
+ """
+ Information parsed from downloading media being previewed.
+ """
+
+ # The Content-Type header of the response.
+ media_type: str
+ # The length (in bytes) of the downloaded media.
+ media_length: int
+ # The media filename, according to the server. This is parsed from the
+ # returned headers, if possible.
+ download_name: Optional[str]
+ # The time of the preview.
+ created_ts_ms: int
+ # Information from the media storage provider about where the file is stored
+ # on disk.
+ filesystem_id: str
+ filename: str
+ # The URI being previewed.
+ uri: str
+ # The HTTP response code.
+ response_code: int
+ # The timestamp (in milliseconds) of when this preview expires.
+ expires: int
+ # The ETag header of the response.
+ etag: Optional[str]
+
+
class PreviewUrlResource(DirectServeJsonResource):
+ """
+ Generating URL previews is a complicated task which many potential pitfalls.
+
+ See docs/development/url_previews.md for discussion of the design and
+ algorithm followed in this module.
+ """
+
isLeaf = True
def __init__(
@@ -219,18 +258,17 @@ class PreviewUrlResource(DirectServeJsonResource):
logger.debug("got media_info of '%s'", media_info)
- if _is_media(media_info["media_type"]):
- file_id = media_info["filesystem_id"]
+ if _is_media(media_info.media_type):
+ file_id = media_info.filesystem_id
dims = await self.media_repo._generate_thumbnails(
- None, file_id, file_id, media_info["media_type"], url_cache=True
+ None, file_id, file_id, media_info.media_type, url_cache=True
)
og = {
- "og:description": media_info["download_name"],
- "og:image": "mxc://%s/%s"
- % (self.server_name, media_info["filesystem_id"]),
- "og:image:type": media_info["media_type"],
- "matrix:image:size": media_info["media_length"],
+ "og:description": media_info.download_name,
+ "og:image": f"mxc://{self.server_name}/{media_info.filesystem_id}",
+ "og:image:type": media_info.media_type,
+ "matrix:image:size": media_info.media_length,
}
if dims:
@@ -240,14 +278,14 @@ class PreviewUrlResource(DirectServeJsonResource):
logger.warning("Couldn't get dims for %s" % url)
# define our OG response for this media
- elif _is_html(media_info["media_type"]):
+ elif _is_html(media_info.media_type):
# TODO: somehow stop a big HTML tree from exploding synapse's RAM
- with open(media_info["filename"], "rb") as file:
+ with open(media_info.filename, "rb") as file:
body = file.read()
- encoding = get_html_media_encoding(body, media_info["media_type"])
- og = decode_and_calc_og(body, media_info["uri"], encoding)
+ encoding = get_html_media_encoding(body, media_info.media_type)
+ og = decode_and_calc_og(body, media_info.uri, encoding)
# pre-cache the image for posterity
# FIXME: it might be cleaner to use the same flow as the main /preview_url
@@ -255,14 +293,14 @@ class PreviewUrlResource(DirectServeJsonResource):
# just rely on the caching on the master request to speed things up.
if "og:image" in og and og["og:image"]:
image_info = await self._download_url(
- _rebase_url(og["og:image"], media_info["uri"]), user
+ _rebase_url(og["og:image"], media_info.uri), user
)
- if _is_media(image_info["media_type"]):
+ if _is_media(image_info.media_type):
# TODO: make sure we don't choke on white-on-transparent images
- file_id = image_info["filesystem_id"]
+ file_id = image_info.filesystem_id
dims = await self.media_repo._generate_thumbnails(
- None, file_id, file_id, image_info["media_type"], url_cache=True
+ None, file_id, file_id, image_info.media_type, url_cache=True
)
if dims:
og["og:image:width"] = dims["width"]
@@ -270,12 +308,11 @@ class PreviewUrlResource(DirectServeJsonResource):
else:
logger.warning("Couldn't get dims for %s", og["og:image"])
- og["og:image"] = "mxc://%s/%s" % (
- self.server_name,
- image_info["filesystem_id"],
- )
- og["og:image:type"] = image_info["media_type"]
- og["matrix:image:size"] = image_info["media_length"]
+ og[
+ "og:image"
+ ] = f"mxc://{self.server_name}/{image_info.filesystem_id}"
+ og["og:image:type"] = image_info.media_type
+ og["matrix:image:size"] = image_info.media_length
else:
del og["og:image"]
else:
@@ -301,17 +338,17 @@ class PreviewUrlResource(DirectServeJsonResource):
# store OG in history-aware DB cache
await self.store.store_url_cache(
url,
- media_info["response_code"],
- media_info["etag"],
- media_info["expires"] + media_info["created_ts"],
+ media_info.response_code,
+ media_info.etag,
+ media_info.expires + media_info.created_ts_ms,
jsonog,
- media_info["filesystem_id"],
- media_info["created_ts"],
+ media_info.filesystem_id,
+ media_info.created_ts_ms,
)
return jsonog.encode("utf8")
- async def _download_url(self, url: str, user: str) -> Dict[str, Any]:
+ async def _download_url(self, url: str, user: str) -> MediaInfo:
# TODO: we should probably honour robots.txt... except in practice
# we're most likely being explicitly triggered by a human rather than a
# bot, so are we really a robot?
@@ -423,18 +460,18 @@ class PreviewUrlResource(DirectServeJsonResource):
# therefore not expire it.
raise
- return {
- "media_type": media_type,
- "media_length": length,
- "download_name": download_name,
- "created_ts": time_now_ms,
- "filesystem_id": file_id,
- "filename": fname,
- "uri": uri,
- "response_code": code,
- "expires": expires,
- "etag": etag,
- }
+ return MediaInfo(
+ media_type=media_type,
+ media_length=length,
+ download_name=download_name,
+ created_ts_ms=time_now_ms,
+ filesystem_id=file_id,
+ filename=fname,
+ uri=uri,
+ response_code=code,
+ expires=expires,
+ etag=etag,
+ )
def _start_expire_url_cache_data(self):
return run_as_background_process(
@@ -580,7 +617,7 @@ def get_html_media_encoding(body: bytes, content_type: str) -> str:
def decode_and_calc_og(
body: bytes, media_uri: str, request_encoding: Optional[str] = None
-) -> Dict[str, Optional[str]]:
+) -> JsonDict:
"""
Calculate metadata for an HTML document.
|
