mirror of https://github.com/mastodon/flodgatt
149 lines
5.8 KiB
Rust
149 lines
5.8 KiB
Rust
//! Receives data from Redis, sorts it by `ClientAgent`, and stores it until
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//! polled by the correct `ClientAgent`. Also manages sububscriptions and
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//! unsubscriptions to/from Redis.
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mod message_queues;
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pub use message_queues::{MessageQueues, MsgQueue};
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use crate::{
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config,
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err::RedisParseErr,
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messages::Event,
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parse_client_request::{Stream, Timeline},
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redis_to_client_stream::redis::RedisConn,
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};
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use futures::{Async, Poll};
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use lru::LruCache;
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use std::{collections::HashMap, time::Instant};
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use uuid::Uuid;
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/// The item that streams from Redis and is polled by the `ClientAgent`
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#[derive(Debug)]
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pub struct Receiver {
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redis_connection: RedisConn,
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timeline: Timeline,
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manager_id: Uuid,
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pub msg_queues: MessageQueues,
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clients_per_timeline: HashMap<Timeline, i32>,
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hashtag_cache: LruCache<i64, String>,
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// TODO: eventually, it might make sense to have Mastodon publish to timelines with
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// the tag number instead of the tag name. This would save us from dealing
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// with a cache here and would be consistent with how lists/users are handled.
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}
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impl Receiver {
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/// Create a new `Receiver`, with its own Redis connections (but, as yet, no
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/// active subscriptions).
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pub fn new(redis_cfg: config::RedisConfig) -> Self {
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let redis_connection = RedisConn::new(redis_cfg);
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Self {
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redis_connection,
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timeline: Timeline::empty(),
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manager_id: Uuid::default(),
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msg_queues: MessageQueues(HashMap::new()),
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clients_per_timeline: HashMap::new(),
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hashtag_cache: LruCache::new(1000),
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// should this be a run-time option?
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}
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}
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/// Assigns the `Receiver` a new timeline to monitor and runs other
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/// first-time setup.
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///
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/// Note: this method calls `subscribe_or_unsubscribe_as_needed`,
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/// so Redis PubSub subscriptions are only updated when a new timeline
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/// comes under management for the first time.
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pub fn manage_new_timeline(&mut self, id: Uuid, tl: Timeline, hashtag: Option<String>) {
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self.timeline = tl;
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if let (Some(hashtag), Timeline(Stream::Hashtag(id), _, _)) = (hashtag, tl) {
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self.hashtag_cache.put(id, hashtag.clone());
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self.redis_connection.update_cache(hashtag, id);
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};
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self.msg_queues.insert(id, MsgQueue::new(tl));
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self.subscribe_or_unsubscribe_as_needed(tl);
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}
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/// Set the `Receiver`'s manager_id and target_timeline fields to the appropriate
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/// value to be polled by the current `StreamManager`.
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pub fn configure_for_polling(&mut self, manager_id: Uuid, timeline: Timeline) {
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self.manager_id = manager_id;
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self.timeline = timeline;
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}
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/// Drop any PubSub subscriptions that don't have active clients and check
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/// that there's a subscription to the current one. If there isn't, then
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/// subscribe to it.
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fn subscribe_or_unsubscribe_as_needed(&mut self, timeline: Timeline) {
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let start_time = Instant::now();
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let timelines_to_modify = self.msg_queues.calculate_timelines_to_add_or_drop(timeline);
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// Record the lower number of clients subscribed to that channel
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for change in timelines_to_modify {
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let timeline = change.timeline;
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let hashtag = match timeline {
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Timeline(Stream::Hashtag(id), _, _) => self.hashtag_cache.get(&id),
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_non_hashtag_timeline => None,
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};
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let count_of_subscribed_clients = self
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.clients_per_timeline
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.entry(timeline)
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.and_modify(|n| *n += change.in_subscriber_number)
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.or_insert_with(|| 1);
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// If no clients, unsubscribe from the channel
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if *count_of_subscribed_clients <= 0 {
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self.redis_connection
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.send_unsubscribe_cmd(&timeline.to_redis_raw_timeline(hashtag));
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} else if *count_of_subscribed_clients == 1 && change.in_subscriber_number == 1 {
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self.redis_connection
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.send_subscribe_cmd(&timeline.to_redis_raw_timeline(hashtag));
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}
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}
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if start_time.elapsed().as_millis() > 1 {
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log::warn!("Sending cmd to Redis took: {:?}", start_time.elapsed());
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};
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}
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}
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/// The stream that the ClientAgent polls to learn about new messages.
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impl futures::stream::Stream for Receiver {
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type Item = Event;
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type Error = RedisParseErr;
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/// Returns the oldest message in the `ClientAgent`'s queue (if any).
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///
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/// Note: This method does **not** poll Redis every time, because polling
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/// Redis is significantly more time consuming that simply returning the
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/// message already in a queue. Thus, we only poll Redis if it has not
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/// been polled lately.
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fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> {
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let (timeline, id) = (self.timeline.clone(), self.manager_id);
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loop {
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match self.redis_connection.poll_redis() {
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Ok(Async::Ready(Some((timeline, event)))) => self
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.msg_queues
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.values_mut()
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.filter(|msg_queue| msg_queue.timeline == timeline)
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.for_each(|msg_queue| {
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msg_queue.messages.push_back(event.clone());
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}),
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Ok(Async::NotReady) => break,
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Ok(Async::Ready(None)) => (),
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Err(err) => Err(err)?,
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}
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}
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// Record current time as last polled time
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self.msg_queues.update_time_for_target_queue(id);
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// If the `msg_queue` being polled has any new messages, return the first (oldest) one
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match self.msg_queues.oldest_msg_in_target_queue(id, timeline) {
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Some(value) => Ok(Async::Ready(Some(value))),
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_ => Ok(Async::NotReady),
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}
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}
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}
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