The max inline preview limit was previously increased to 10 by #20789.
However, as issue #23624 shows, it's still causing confusion for users
when they include more than 10 links.
Bump this limit up to 24, which is a multiple of the 4 image preview
per line logic.
Accessing .realm will cause a fetch query from the database if the
attribute hasn't been fetched already earlier in the codepath. That's
completely redundant if we're just comparing realms, and we should only
access .realm_id attribute. This seems to eliminate a query in some
codepaths, which is nice in this performance-sensitive function.
When file uploads are stored in S3, this means that Zulip serves as a
302 to S3. Because browsers do not cache redirects, this means that
no image contents can be cached -- and upon every page load or reload,
every recently-posted image must be re-fetched. This incurs extra
load on the Zulip server, as well as potentially excessive bandwidth
usage from S3, and on the client's connection.
Switch to fetching the content from S3 in nginx, and serving the
content from nginx. These have `Cache-control: private, immutable`
headers set on the response, allowing browsers to cache them locally.
Because nginx fetching from S3 can be slow, and requests for uploads
will generally be bunched around when a message containing them are
first posted, we instruct nginx to cache the contents locally. This
is safe because uploaded file contents are immutable; access control
is still mediated by Django. The nginx cache key is the URL without
query parameters, as those parameters include a time-limited signed
authentication parameter which lets nginx fetch the non-public file.
This adds a number of nginx-level configuration parameters to control
the caching which nginx performs, including the amount of in-memory
index for he cache, the maximum storage of the cache on disk, and how
long data is retained in the cache. The currently-chosen figures are
reasonable for small to medium deployments.
The most notable effect of this change is in allowing browsers to
cache uploaded image content; however, while there will be many fewer
requests, it also has an improvement on request latency. The
following tests were done with a non-AWS client in SFO, a server and
S3 storage in us-east-1, and with 100 requests after 10 requests of
warm-up (to fill the nginx cache). The mean and standard deviation
are shown.
| | Redirect to S3 | Caching proxy, hot | Caching proxy, cold |
| ----------------- | ------------------- | ------------------- | ------------------- |
| Time in Django | 263.0 ms ± 28.3 ms | 258.0 ms ± 12.3 ms | 258.0 ms ± 12.3 ms |
| Small file (842b) | 586.1 ms ± 21.1 ms | 266.1 ms ± 67.4 ms | 288.6 ms ± 17.7 ms |
| Large file (660k) | 959.6 ms ± 137.9 ms | 609.5 ms ± 13.0 ms | 648.1 ms ± 43.2 ms |
The hot-cache performance is faster for both large and small files,
since it saves the client the time having to make a second request to
a separate host. This performance improvement remains at least 100ms
even if the client is on the same coast as the server.
Cold nginx caches are only slightly slower than hot caches, because
VPC access to S3 endpoints is extremely fast (assuming it is in the
same region as the host), and nginx can pool connections to S3 and
reuse them.
However, all of the 648ms taken to serve a cold-cache large file is
occupied in nginx, as opposed to the only 263ms which was spent in
nginx when using redirects to S3. This means that to overall spend
less time responding to uploaded-file requests in nginx, clients will
need to find files in their local cache, and skip making an
uploaded-file request, at least 60% of the time. Modeling shows a
reduction in the number of client requests by about 70% - 80%.
The `Content-Disposition` header logic can now also be entirely shared
with the local-file codepath, as can the `url_only` path used by
mobile clients. While we could provide the direct-to-S3 temporary
signed URL to mobile clients, we choose to provide the
served-from-Zulip signed URL, to better control caching headers on it,
and greater consistency. In doing so, we adjust the salt used for the
URL; since these URLs are only valid for 60s, the effect of this salt
change is minimal.
Moving `/user_avatars/` to being served partially through Django
removes the need for the `no_serve_uploads` nginx reconfiguring when
switching between S3 and local backends. This is important because a
subsequent commit will move S3 attachments to being served through
nginx, which would make `no_serve_uploads` entirely nonsensical of a
name.
Serve the files through Django, with an offload for the actual image
response to an internal nginx route. In development, serve the files
directly in Django.
We do _not_ mark the contents as immutable for caching purposes, since
the path for avatar images is hashed only by their user-id and a salt,
and as such are reused when a user's avatar is updated.
Importing `upload_backend` directly means that in testing it must also
be mocked where it is imported, in order to correctly test the right
backend. Since `get_avatar_url` is part of the public
`ZulipUploadBackend` API, add another helper method to call that.
The `django-sendfile2` module unfortunately only supports a single
`SENDFILE` root path -- an invariant which subsequent commits need to
break. Especially as Zulip only runs with a single webserver, and
thus sendfile backend, the functionality is simple to inline.
It is worth noting that the following headers from the initial Django
response are _preserved_, if present, and sent unmodified to the
client; all other headers are overridden by those supplied by the
internal redirect[^1]:
- Content-Type
- Content-Disposition
- Accept-Ranges
- Set-Cookie
- Cache-Control
- Expires
As such, we explicitly unset the Content-type header to allow nginx to
set it from the static file, but set Content-Disposition and
Cache-Control as we want them to be.
[^1]: https://www.nginx.com/resources/wiki/start/topics/examples/xsendfile/
Enforcing a consistent `type` helps us double-check that we're not
playing fast-and-loose with any file paths for local files. As noted
in the comment, this is purely for defense-in-depth.
Passing `write_local_file` a consistent `type` requires removing the
"avatars" out of `realm_avatar_and_logo_path` -- which makes it
consistent across upload backends.
This, in turn, requires a compensatory change to zerver.lib.export, to
be explicit that the realm icons are exported from the avatars
directory. This clarity is likely an improvement.
Updates the help center article to match the style and formatting
of "Import from Slack" and replaces existing content with its
corresponding Markdown macro.
‘logging.warning("Naive datetime:", item)’ is an invalid call that
crashes with “TypeError: not all arguments converted during string
formatting”. I take that to mean this check has not been tripped in
the six years it’s been there, and can safely be replaced with an
error.
Signed-off-by: Anders Kaseorg <anders@zulip.com>
Some email clients (notably, Gmail Web) support automatically threading
emails together if recipients and subjects match[1]. Manual testing
indicated that prefixing a subject with "[bracketed content]" does not
break this threading behavior, but the added checkmark in a resolved
topic's title does. Before sending an email notification, determine
whether the topic is resolved, and pass this information to the Jinja
template to properly format a threadable email subject.
Fixes: #22538
[1]: https://support.google.com/mail/answer/5900
Previously, stream names and topics (without consideration for their
resolution status) were concatenated in Python-land and passed through
to the template. To more cleanly separate concerns, and to prepare for
accounting for topic resolution status being a third, independent,
component of a subject line, instead pass stream and topic strings
independently to the Jinja template, which can format them as it sees
fit.
Additionally, migrate existing EditMessageTest to use this helper
method, with the side effect of migrating the tested flow from a
/json/messages URL to a /api/v1/messages URL.
This uses the linkifier index among the list of linkifiers in the
replacement as the priority to order the replacement order for
patterns in the topic. This avoids having multiple overlapping matches
that each produce a link.
The linkifier with the lowest id will be prioritized when its pattern
overlaps with another. Linkifiers are prioritized over raw URLs.
Note that the same algorithm is used for local echoing and the
backend markdown processor.
Fixes#23715.
Signed-off-by: Zixuan James Li <p359101898@gmail.com>
The same pattern being matched multiple times in a topic cannot be
properly ordered using topic_name.find(match_text) and etc. when there
are multiple matches of the same pattern in the topic.
Signed-off-by: Zixuan James Li <p359101898@gmail.com>
Moves files in `templates/zerver/help/include` that are used
specifically for API documentation pages to be in a new directory:
`templates/zerver/api/include`.
Adds a boolean parameter to `render_markdown_path` to be used
for help center documentation articles.
Also moves the test file `empty.md` to the new directory since
this is the default directory for these special include macros
that are used in documentation pages.
Moves files in `templates/zerver/help/include` that are used
specifically for integrations documentation to be in a new
directory: `templates/zerver/integrations/include`.
Adds a boolean parameter to `render_markdown_path` to be used
for integrations documentation pages.
As we have seen no further cases of this in production since #23215,
increase the severity to an error, and switch from returning a
list (which is not type-safe if the function declares a QuerySet
return) to returning the QuerySet without caching.
Failing to store the result in the cache, with an error, seems
superior to raising an exception; in both cases the next request will
redo the work, but we are guaranteed a worse user experience if we 500
the request.
Ref https://github.com/zulip/zulip/pull/23215#discussion_r994186493
remove_user_from_user_group's only caller has been removed in 271333301d.
Its usage has been superseded by remove_members_from_user_group.
Signed-off-by: Zixuan James Li <p359101898@gmail.com>
