We no bulk up peer_add/peer_remove events by user if the
same user has subscribed to multiple streams (and just
that single user).
This mostly optimizes the new-user codepath, but the
algorithm is a bit more general in nature.
See commit 8b002040e0 and #86. The
development environment bug that necessitated this handler has long
been irrelevant.
Signed-off-by: Anders Kaseorg <anders@zulip.com>
We now can send an implied matrix of user/stream tuples
for peer_add and peer_remove events.
The client code basically does this:
for stream_id in event['stream_ids']:
for user_id in event['user_ids']:
update_sub(stream_id, user_id)
We used to send individual events, which gets real
expensive when you are creating new streams. For
the case of copy-to-stream case, we should see
events go from U to 1, where U is the number of users
added.
Note that we don't yet fully optimize the potential
of this schema. For adding a new user with lots
of default streams, we still send S peer_add events.
And if you subscribe a bunch of users to a bunch of
private streams, we only go from U * S to S; we can't
optimize it down to one event easily.
All the fields of a stream's recipient object can
be inferred from the Stream, so we just make a local
object. Django will create a Message object without
checking that the child Recipient object has been
saved. If that behavior changes in some upgrade,
we should see some pretty obvious symptom, including
query counts changing.
Tweaked by tabbott to add a longer explanatory comment, and delete a
useless old comment.
This saves us a query for edge cases like when
you try to unsubscribe from a public stream
that you have already unsubscribed from.
But this is mostly to prep for upcoming
optimizations.
This doesn't change anything yet, but the goal is
to eventually optimize events for the case where
one user (typically a new user) gets subscribed
to multiple public streams.
Initially markdown titles were overridden by Youtube and Vimeo preview titles.
But now it will check if any markdown title is present to replace Youtube or
Vimeo preview titles, if preview of linked websites is enabled.
Fixes#16100
Upstream has slightly changed the whitespace around stashes. Take
this opportunity to clean up the extra blank lines we were outputting.
Signed-off-by: Anders Kaseorg <anders@zulip.com>
There was no need to put "stream_id" on the sub
dictionary here. It's kinda annoying to introduce
the little helper here, but I feel
that's better than crufting up the sub data
structure.
The is_web_public flag is already in Stream.API_FIELDS,
so there is no reason for all this complicated logic.
There's no reason to hack it on to the subscription
object.
We replace all_streams_id with a map.
We also use it to populate never_subscribed_streams.
And all_streams_map is a superset of stream_hash,
which we will soon kill off as well.
Apparently I put these parens in the code as
part of 73c30774cb
during 2017.
It looks like I extracted is_public during
the middle of my change and forgot to remove
the unnecessary parens. (The code was correct,
but it makes it look like a tuple if you're
skimming it too quickly.)
That class is an artifact of when Stream
didn't have recipient_id. Now it's simpler
to deal with stream subscriptions.
We also save a query during page load (and
other places where we get subscriber
info).
Let the callers access stream.recipient as needed.
It costs the same, and some of the callers can
actually stop caring about the actual Recipient
object.
We already trust ids that are put on our queue
for deferred work. For example, see the code for
"mark_stream_messages_as_read_for_everyone"
We now pass stream_recipient_id when we queue
up work for do_mark_stream_messages_as_read.
This generally saves about 3 queries per
user when we unsubscribe them from a stream.
We get two speedups:
* The query to get existing subscribers only
gets the two fields we need. We no longer
need all the overhead of user_profile
and recipient data being returned in the
query.
* We avoid Django making extra hops to the
database to get user info.
Previously, the transaction.atomic() was not properly scoped to ensure
that RealmAuditLog entries were created in the same transaction,
making it possible for state changes to not be properly recorded in
RealmAuditLog.
When apps like mobile register for "streams", we
will now just use active streams as our baseline,
rather than "occupied" streams.
This means we will send a stream that is active,
even if it happens to have zero occupants. It's
actually pretty rare that a stream has zero occupants,
and it's not exactly clear that we want to exclude
a non-occupied but otherwise active stream from
our list of streams.
It also happens to be fairly expensive to compute
whether a stream is occupied.
This change only affects API clients (including
possibly our mobile app). The main webapp never
used the data from this codepath.
We replace get_peer_user_ids_for_stream_change
with two bulk functions to get peers and/or
subscribers.
Note that we have three codepaths that care about
peers:
subscribing existing users:
we need to tell peers about new subscribers
we need to tell subscribed user about old subscribers
unsubscribing existing users:
we only need to tell peers who unsubscribed
subscribing new user:
we only need to tell peers about the new user
(right now we generate send_event
calls to tell the new user about existing
subscribers, but this is a waste
of effort that we will fix soon)
The two bulk functions are this:
bulk_get_subscriber_peer_info
bulk_get_peers
They have some overlap in the implementation,
but there are some nuanced differences that are
described in the comments.
Looking up peers/subscribers in bulk leads to some
nice optimizations.
We will save some memchached traffic if you are
subscribing to multiple public streams.
We will save a query in the remove-subscriber
case if you are only dealing with private streams.
This will ensure that we always fully execute the database part of
modifying subscription objects. In particular, this should prevent
invariant failures like #16347 where Subscription objects were created
without corresponding RealmAuditLog entries.
Fixes#16347.
We don't need the select_related('user_profile')
optimization any more, because we just keep
track of user info in our own data structures.
In this codepath we are never actually modifying
users; we just occasionally need their ids or
emails.
This can be a pretty substantive improvement if
you are adding a bunch of users to a stream
who each have a bunch of their own subscriptions.
We could also limit the number of full rows in this
query by adding an extra hop to the DB just to
get colors (using values_list), and then only get
full sub info for the streams that we're adding, rather
than getting every single subscription, in full, for each user.
Apart from finding what colors the user has already
used, the only other reason we need all the columns
in Subscription here is to handle streams that
need to be reactivated. Otherwise we could do
only("id", "active", "recipient_id", "user_profile_id")
or similar. Fortunately, Subscription isn't
an overly wide table; it's mostly bool fields.
But by far the biggest thing to avoid is bringing
in all the extra user_profile data.
We have pretty good coverage on query counts here,
so I think this fix is pretty low risk.
This class removes a lot of the annoying tuples
we were passing around.
Also, by including the user everywhere, which
is easily available to us when we make instances
of SubInfo, it sets the stage to remove
select_related('user_profile').
We used to send occupy/vacate events when
either the first person entered a stream
or the last person exited.
It appears that our two main apps have never
looked at these events. Instead, it's
generally the case that clients handle
events related to stream creation/deactivation
and subscribe/unsubscribe.
Note that we removed the apply_events code
related to these events. This doesn't affect
the webapp, because the webapp doesn't care
about the "streams" field in do_events_register.
There is a theoretical situation where a
third party client could be the victim of
a race where the "streams" data includes
a stream where the last subscriber has left.
I suspect in most of those situations it
will be harmless, or possibly even helpful
to the extent that they'll learn about
streams that are in a "quasi" state where
they're activated but not occupied.
We could try to patch apply_event to
detect when subscriptions get added
or removed. Or we could just make the
"streams" piece of do_events_register
not care about occupy/vacate semantics.
I favor the latter, since it might
actually be what users what, and it will
also simplify the code and improve
performance.
The query to get "occupied" streams has been expensive
in the past. I'm not sure how much any recent attempts
to optimize that query have mitigated the issue, but
since we clearly aren't sending this data, there is no
reason to compute it.
Using web_public_guest for anonymous users is confusing since
'guest' is actually a logged-in user compared to
web_public_guest which is not logged-in and has only
read access to messages. So, we rename it to
web_public_visitor.
We no longer do O(N) queries to get existing streams.
This is a somewhat contrived use case--generally, we
are not trying to re-subscribe a user to several
streams. Still, we want to avoid this.
This commit also makes `test_bulk_subscribe_many`
do more work, and the change to the test helped
me discover this bug.
If a user asks to be subscribed to a stream
that they are already subscribed to, then
that stream won't be in new_stream_user_ids,
and we won't need to send an event for it.
This change makes that happen more automatically.
Let
U = number of users to subscribe
S = number of streams to subscribe
We were technically doing N^3 amount of work
when we sent certain events, or to be more
precise, U * S * S amount of work. For each
stream, we were looping through a list of tuples
of size U * S to find the users for the stream.
In practice either U or S is usually 1, so the
performance gains here are probably negligible,
especially since the constant factors here
were just slinging around Python data.
But the code is actually more readable now, so
it's a double win.
We rename needs_new_sub (which sounds like
a boolean!) to new_recipient_ids, and we
calculate it explicitly within the loop, so
that we don't need to worry as much about
subsequent passes through the loop mutating it.
This allows us to also remove recipient_ids,
which in turn lets us remove recipients_map,
albeit with a small tweak for stream_map.
I also introduce the my_subs local, which
I use to more directly populate used_colors,
as well as using it as the loop var.
I think it's important that the callers understand
that bulk_add_subscriptions assumes all streams
are being created within a single realm, so I make
it an explicit parameter.
This may be overkill--I would also be happy if we
just included the assertions from this commit.
This function now does all the work that we used
to do with notify_subscriptions_added happening
inside a loop.
There's a small fine-tuning here, where we only
get recent traffic on streams that we're actually
sending events for.
We now just pass in all_subscribers_by_stream, rather
than a callback.
We also move sub_tuples_by_user closer to the
loop where we call notify_subscriptions_added.
This preserves the alpha layer on GIF images that need to be resized
before being uploaded. Two important changes occur here:
1. The new frame is a *copy* of the original image, which preserves the
GIF info.
2. The disposal method of the original GIF is preserved. This
essentially determines what state each frame of the GIF starts from
when it is drawn; see PIL's docs:
https://pillow.readthedocs.io/en/stable/handbook/image-file-formats.html#saving
for more info.
This resolves some but not all of the test cases in #16370.
This low-level interface allows consuming from a queue with timeouts.
This can be used to either consume in batches (with an upper timeout),
or one-at-a-time. This is notably more performant than calling
`.get()` repeatedly (what json_drain_queue does under the hood), which
is "*highly discouraged* as it is *very inefficient*"[1].
Before this change:
```
$ ./manage.py queue_rate --count 10000 --batch
Purging queue...
Enqueue rate: 11158 / sec
Dequeue rate: 3075 / sec
```
After:
```
$ ./manage.py queue_rate --count 10000 --batch
Purging queue...
Enqueue rate: 11511 / sec
Dequeue rate: 19938 / sec
```
[1] https://www.rabbitmq.com/consumers.html#fetching
Despite its name, the `queue_size` method does not return the number
of items in the queue; it returns the number of items that the local
consumer has delivered but unprocessed. These are often, but not
always, the same.
RabbitMQ's queues maintain the queue of unacknowledged messages; when
a consumer connects, it sends to the consumer some number of messages
to handle, known as the "prefetch." This is a performance
optimization, to ensure the consumer code does not need to wait for a
network round-trip before having new data to consume.
The default prefetch is 0, which means that RabbitMQ immediately dumps
all outstanding messages to the consumer, which slowly processes and
acknowledges them. If a second consumer were to connect to the same
queue, they would receive no messages to process, as the first
consumer has already been allocated them. If the first consumer
disconnects or crashes, all prior events sent to it are then made
available for other consumers on the queue.
The consumer does not know the total size of the queue -- merely how
many messages it has been handed.
No change is made to the prefetch here; however, future changes may
wish to limit the prefetch, either for memory-saving, or to allow
multiple consumers to work the same queue.
Rename the method to make clear that it only contains information
about the local queue in the consumer, not the full RabbitMQ queue.
Also include the waiting message count, which is used by the
`consume()` iterator for similar purpose to the pending events list.
We modify access_stream_for_delete_or_update function to return
Subscription object also along with stream. This change will be
helpful in avoiding an extra query to get subscription object in
code for updating subscription role.
For streams in which only full members are allowed to post,
we block guest users from posting there.
Guests users were blocked from posting to admin only streams
already. So now, guest users can only post to
STREAM_POST_POLICY_EVERYONE streams.
This is not a new feature but a bugfix which should have
happened when implementing full member stream policy / guest users.
Replaced ImageOps.fit by ImageOps.pad, in zerver/lib/upload.py, which
returns a sized and padded version of the image, expanded to fill the
requested aspect ratio and size.
Fixes part of #16370.
Currently, drain_queue and json_drain_queue ack every message as it is
pulled off of the queue, until the queue is empty. This means that if
the consumer crashes between pulling a batch of messages off the
queue, and actually processing them, those messages will be
permanently lost. Sending an ACK on every message also results in a
significant amount lot of traffic to rabbitmq, with notable
performance implications.
Send a singular ACK after the processing has completed, by making
`drain_queue` into a contextmanager. Additionally, use the `multiple`
flag to ACK all of the messages at once -- or explicitly NACK the
messages if processing failed. Sending a NACK will re-queue them at
the front of the queue.
Performance of a no-op dequeue before this change:
```
$ ./manage.py queue_rate --count 50000 --batch
Purging queue...
Enqueue rate: 10847 / sec
Dequeue rate: 2479 / sec
```
Performance of a no-op dequeue after this change (a 25% increase):
```
$ ./manage.py queue_rate --count 50000 --batch
Purging queue...
Enqueue rate: 10752 / sec
Dequeue rate: 3079 / sec
```
Part of #16094.
Moved the language selection preference logic from home.py to a new
function in i18n.py to avoid repetition in analytics views and home
views.
Steve Howell
Anders Kaseorg
sahil839
akshatdalton
Tim Abbott
Aman Agrawal
Cody Piersall
Alex Vandiver
Abhijeet Prasad Bodas