This is done synchronously, despite taking ~60s. We can move it to a
background thread later if that's an issue, but generally Prometheus
is tolerant to exporters taking a while to come back with results.
This provides access logging metrics to Prometheus. For cardinality
reasons, we cannot (nor would we want to) put every request path into
its own label value -- but we do separate out the most-frequent access
paths (as well as some low-frequency but high-interest ones) into
their own label values.
In order to differentiate accesses to https://zulip.com/ from
https://example.zulipchat.com/ (both of which appear at path `/`), we
use a `grok_exporter.realm_names_regex` value in `zulip.conf`, which
is expected to be set to match the hostname of all possible realms.
`deliver_scheduled_emails` tries to deliver the email synchronously,
and if it fails, it retries after 10 seconds. Since it does not track
retries, and always tries the earliest-scheduled-but-due message
first, the worker will not make forward progress if there is a
persistent failure with that message, and will retry indefinitely.
This can result in excessive network or email delivery charges from
the remote SMTP server.
Switch to delivering emails via a new queue worker. The
`deliver_scheduled_emails` job now serves only to pull deferred jobs
out of the table once they are due, insert them into RabbitMQ, and
then delete them. This limits the potential for head-of-queue
failures to failures inserting into RabbitMQ, which is more reasonable
than failures speaking to a complex external system we do not control.
Retries and any connections to the SMTP server are left to the
RabbitMQ consumer.
We build a new RabbitMQ queue, rather than use the existing
`email_senders` queue, because that queue is expected to be reasonably
low-latency, for things like missed message notifications. The
`send_future_email` codepath which inserts into ScheduledEmails is
also (ab)used to digest emails, which are extremely bursty in their
frequency -- and a large burst could significantly delay emails behind
it in the queue.
The new queue is explicitly only for messages which were not initiated
by user actions (e.g., invitation reminders, digests, new account
follow-ups) which are thus not latency-sensitive.
Fixes: #32463.
A new table is created to track which path_id attachments are images,
and for those their metadata, and which thumbnails have been created.
Using path_id as the effective primary key lets us ignore if the
attachment is archived or not, saving some foreign key messes.
A new worker is added to observe events when rows are added to this
table, and to generate and store thumbnails for those images in
differing sizes and formats.
