| Commit message (Collapse) | Author | Age |
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To make unread handling of empty channels coherent (and to make it possible to mark an empty channel as having been read), they need to be associated with a specific point in time. This change exposes their creation time in the snapshot - it was already part of the event view, though the client doesn't know that yet.
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There may be other instances of this, this is just the one I found recently.
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A heartbeat is an event that the server synthesizes any time an event stream has been idle for longer than some timeout. They allow clients to detect disconnection and network problems, which would otherwise go unnoticed because event streams are a one-way channel. Most network problems only become clear when the offended party tries to _send_ something, and subscribing to an event stream only sends something during the request phase.
Technically, Pilcrow has always sent these, since we started using Axum's SSE support: it defaults to sending a dummy event after 15 seconds (consisting of `":\n\n"`, which is then ignored). I've built Pilcrow's heartbeat support out of that, by customizing the event sent back. The results _mostly_ look like existing events, but there are two key differences:
* Heartbeats don't have `id` fields in the event stream. They're synthetic, and they don't participate in either the "resume at" sequence management, or the last-event-id header-based resumption management.
* Heartbeats have an `event` but no `type` field in the message body. There are no subtypes.
To make it less likely that clients will race with the server on expiring timeouts, heartbeats are sent about five seconds early. In this change, heartbeats are due after 20 seconds, but are sent after 15. If it takes longer than five seconds for a heartbeat to arrive, a client can and should treat that as a network problem and reconnect, but I'd really like to avoid that happening over differences smaller than a second, so I've left a margin.
I originally sketched this out in conversation with @wlonk as having each event carry a deadline for the next one. I ultimately opted not to do that for a few reasons. First, Axum makes it hard - the built-in keep-alive support only works with a static event, and cannot make dynamic ones whose payloads might vary (for example if the deadline is variable). Second, it's complex, to no apparent gain, and adds deadline information to _every_ event type.
This implementation, instead, sends deadline information as part of boot, as a fixed interval in seconds. Clients are responsible for working out deadlines based on message arrivals. This is fine; heartbeat-based connection management is best effort at the best of times, so a few milliseconds of slop in either direction won't hurt anything.
The existing client ignores these events entirely, which is convenient.
The new heartbeat event type is defined alongside the main event type, to make it less likely that we'll inadvertently make changes to one but not the other. We can still do so advertently, I just don't want it to be an accident.
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This is an inconsequential change for actual clients, since "resume from the beginning" was never a preferred mode of operation, and it simplifies some internals. It should also mean we get better query plans where `coalesce(cond, true)` was previously being used.
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The protocol here re-checks the caller's password, as a "I left myself logged in" anti-pranking check.
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Thankfully, channel creation only happens in one place, so we don't need a state machine for this.
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There's no good reason to use an empty string as your login name, or to use one so long as to annoy others. Names beginning or ending with whitespace, or containing runs of whitespace, are also a technical problem, so they're also prohibited.
This change does not implement [UTS #39], as I haven't yet fully understood how to do so.
[UTS #39]: https://www.unicode.org/reports/tr39/
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return the ID of the affected entity.
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Canonicalization does two things:
* It prevents duplicate names that differ only by case or only by normalization/encoding sequence; and
* It makes certain name-based comparisons "case-insensitive" (generalizing via Unicode's case-folding rules).
This change is complicated, as it means that every name now needs to be stored in two forms. Unfortunately, this is _very likely_ a breaking schema change. The migrations in this commit perform a best-effort attempt to canonicalize existing channel or login names, but it's likely any existing channels or logins with non-ASCII characters will not be canonicalize correctly. Since clients look at all channel names and all login names on boot, and since the code in this commit verifies canonicalization when reading from the database, this will effectively make the server un-usuable until any incorrectly-canonicalized values are either manually canonicalized, or removed
It might be possible to do better with [the `icu` sqlite3 extension][icu], but (a) I'm not convinced of that and (b) this commit is already huge; adding database extension support would make it far larger.
[icu]: https://sqlite.org/src/dir/ext/icu
For some references on why it's worth storing usernames this way, see <https://www.b-list.org/weblog/2018/nov/26/case/> and the refernced talk, as well as <https://www.b-list.org/weblog/2018/feb/11/usernames/>. Bennett's treatment of this issue is, to my eye, much more readable than the referenced Unicode technical reports, and I'm inclined to trust his opinion given that he maintains a widely-used, internet-facing user registration library for Django.
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This normalizes the following values:
* login names
* passwords
* channel names
* message bodies, because why not
The goal here is to have a canonical representation of these values, so that, for example, the service does not inadvertently host two channels whose names are semantically identical but differ in the specifics of how diacritics are encoded, or two users whose names are identical.
Normalization is done on input from the wire, using Serde hooks, and when reading from the database. The `crate::nfc::String` type implements these normalizations (as well as normalizing whenever converted from a `std::string::String` generally).
This change does not cover:
* Trying to cope with passwords that were created as non-normalized strings, which are now non-verifiable as all the paths to verify passwords normalize the input.
* Trying to ensure that non-normalized data in the database compares reasonably to normalized data. Fortunately, we don't _do_ very many string comparisons (I think only login names), so this isn't a huge deal at this stage. Login names will probably have to Get Fixed later on, when we figure out how to handle case folding for login name verification.
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messages.
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In general:
* If the client can only assume the response is immediately valid (mostly, login creation, where the client cannot monitor the event stream), then 200 Okay, with data describing the server's view of the request.
* If the client can monitor for completion by watching the event stream, then 202 Accepted, with data describing the server's view of the request.
This comes on the heels of a comment I made on Discord:
> hrm
>
> creating a login: 204 No Content, no body
> sending a message: 202 Accepted, no body
> creating a channel: 200 Okay, has a body
>
> past me, what were you on
There wasn't any principled reason for this inconsistency; it happened as the endpoints were written at different times and with different states of mind.
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events in the docs.
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Previously, when a channel (message) was deleted, `hi` would send events to all _connected_ clients to inform them of the deletion, then delete all memory of the channel (message). Any disconnected client, on reconnecting, would not receive the deletion event, and would de-synch with the service. The creation events were also immediately retconned out of the event stream, as well.
With this change, `hi` keeps a record of deleted channels (messages). When replaying events, these records are used to replay the deletion event. After 7 days, the retained data is deleted, both to keep storage under control and to conform to users' expectations that deleted means gone.
To match users' likely intuitions about what deletion does, deleting a channel (message) _does_ immediately delete some of its associated data. Channels' names are blanked, and messages' bodies are also blanked. When the event stream is replayed, the original channel.created (message.sent) event is "tombstoned", with an additional `deleted_at` field to inform clients. The included client does not use this field, at least yet.
The migration is, once again, screamingingly complicated due to sqlite's limited ALTER TABLE … ALTER COLUMN support.
This change also contains capabilities that would allow the API to return 410 Gone for deleted channels or messages, instead of 404. I did experiment with this, but it's tricky to do pervasively, especially since most app-level interfaces return an `Option<Channel>` or `Option<Message>`. Redesigning these to return either `Ok(Channel)` (`Ok(Message)`) or `Err(Error::NotFound)` or `Err(Error::Deleted)` is more work than I wanted to take on for this change, and the utility of 410 Gone responses is not obvious to me. We have other, more pressing API design warts to address.
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This is mostly a how-to-Svelte thing.
I've also made the API responses for invites a bit more caller-friendly by flattening them and adding the ID field into them. The ID is redundant (the client knows it because the client has the invitation URL), but it makes presenting invitations and actioning them a bit easier.
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Having the whole API in a single file was starting to feel very cramped and constraining. This rewrite breaks it out into sections; as a side effect, the docs are now about 2.5x as long as they were, as the rewrite allows more space for each idea without crowding the page.
The docs are best read by running `tools/docs-api`.
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