mirror of https://github.com/mastodon/flodgatt
273 lines
10 KiB
Rust
273 lines
10 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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use super::redis_cmd;
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use crate::{config, pubsub_cmd};
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use futures::{Async, Poll};
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use log::info;
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use regex::Regex;
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use serde_json::Value;
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use std::{collections, io::Read, io::Write, net, time};
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use tokio::io::{AsyncRead, Error};
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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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pubsub_connection: net::TcpStream,
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secondary_redis_connection: net::TcpStream,
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redis_polled_at: time::Instant,
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timeline: String,
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manager_id: Uuid,
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msg_queues: collections::HashMap<Uuid, MsgQueue>,
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clients_per_timeline: collections::HashMap<String, i32>,
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incoming_raw_msg: String,
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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() -> Self {
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let (pubsub_connection, secondary_redis_connection) = config::redis_addr();
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Self {
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pubsub_connection,
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secondary_redis_connection,
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redis_polled_at: time::Instant::now(),
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timeline: String::new(),
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manager_id: Uuid::default(),
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msg_queues: collections::HashMap::new(),
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clients_per_timeline: collections::HashMap::new(),
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/// The unprocessed message from Redis, consisting of 0 or more
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/// actual `messages` in the sense of updates to send.
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incoming_raw_msg: String::new(),
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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, manager_id: Uuid, timeline: &str) {
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self.manager_id = manager_id;
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self.timeline = timeline.to_string();
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self.msg_queues
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.insert(self.manager_id, MsgQueue::new(timeline));
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self.subscribe_or_unsubscribe_as_needed(timeline);
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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: &str) {
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self.manager_id = manager_id;
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self.timeline = timeline.to_string();
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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: &str) {
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let mut timelines_to_modify = Vec::new();
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struct Change {
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timeline: String,
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change_in_subscriber_number: i32,
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}
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timelines_to_modify.push(Change {
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timeline: timeline.to_owned(),
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change_in_subscriber_number: 1,
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});
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// Keep only message queues that have been polled recently
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self.msg_queues.retain(|_id, msg_queue| {
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if msg_queue.last_polled_at.elapsed() < time::Duration::from_secs(30) {
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true
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} else {
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let timeline = &msg_queue.redis_channel;
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timelines_to_modify.push(Change {
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timeline: timeline.to_owned(),
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change_in_subscriber_number: -1,
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});
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false
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}
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});
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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 mut need_to_subscribe = false;
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let count_of_subscribed_clients = self
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.clients_per_timeline
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.entry(change.timeline.clone())
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.and_modify(|n| *n += change.change_in_subscriber_number)
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.or_insert_with(|| {
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need_to_subscribe = true;
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1
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});
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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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pubsub_cmd!("unsubscribe", self, change.timeline.clone());
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}
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if need_to_subscribe {
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pubsub_cmd!("subscribe", self, change.timeline.clone());
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}
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}
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}
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fn log_number_of_msgs_in_queue(&self) {
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let messages_waiting = self
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.msg_queues
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.get(&self.manager_id)
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.expect("Guaranteed by match block")
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.messages
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.len();
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match messages_waiting {
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number if number > 10 => {
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log::error!("{} messages waiting in the queue", messages_waiting)
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}
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_ => log::info!("{} messages waiting in the queue", messages_waiting),
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}
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}
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fn get_target_msg_queue(&mut self) -> collections::hash_map::Entry<Uuid, MsgQueue> {
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self.msg_queues.entry(self.manager_id)
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}
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}
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impl Default for Receiver {
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fn default() -> Self {
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Receiver::new()
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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 = Value;
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type Error = Error;
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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 signifiantly 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<Value>, Self::Error> {
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let timeline = self.timeline.clone();
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if self.redis_polled_at.elapsed()
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> time::Duration::from_millis(*config::REDIS_POLL_INTERVAL)
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{
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AsyncReadableStream::poll_redis(self);
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self.redis_polled_at = time::Instant::now();
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}
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// Record current time as last polled time
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self.get_target_msg_queue()
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.and_modify(|msg_queue| msg_queue.last_polled_at = time::Instant::now());
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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
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.get_target_msg_queue()
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.or_insert_with(|| MsgQueue::new(timeline.clone()))
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.messages
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.pop_front()
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{
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Some(value) => {
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self.log_number_of_msgs_in_queue();
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Ok(Async::Ready(Some(value)))
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}
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_ => Ok(Async::NotReady),
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}
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}
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}
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impl Drop for Receiver {
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fn drop(&mut self) {
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pubsub_cmd!("unsubscribe", self, self.timeline.clone());
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}
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}
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#[derive(Debug, Clone)]
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struct MsgQueue {
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messages: collections::VecDeque<Value>,
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last_polled_at: time::Instant,
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redis_channel: String,
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}
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impl MsgQueue {
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fn new(redis_channel: impl std::fmt::Display) -> Self {
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let redis_channel = redis_channel.to_string();
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MsgQueue {
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messages: collections::VecDeque::new(),
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last_polled_at: time::Instant::now(),
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redis_channel,
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}
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}
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}
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struct AsyncReadableStream<'a>(&'a mut net::TcpStream);
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impl<'a> AsyncReadableStream<'a> {
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fn new(stream: &'a mut net::TcpStream) -> Self {
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AsyncReadableStream(stream)
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}
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/// Polls Redis for any new messages and adds them to the `MsgQueue` for
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/// the appropriate `ClientAgent`.
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fn poll_redis(receiver: &mut Receiver) {
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let mut buffer = vec![0u8; 3000];
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let mut async_stream = AsyncReadableStream::new(&mut receiver.pubsub_connection);
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if let Async::Ready(num_bytes_read) = async_stream.poll_read(&mut buffer).unwrap() {
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let raw_redis_response = &String::from_utf8_lossy(&buffer[..num_bytes_read]);
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dbg!(&raw_redis_response);
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receiver.incoming_raw_msg.push_str(raw_redis_response);
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// Text comes in from redis as a raw stream, which could be more than one message
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// and is not guaranteed to end on a message boundary. We need to break it down
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// into messages. First, start by only acting if we end on a valid message boundary
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if receiver.incoming_raw_msg.ends_with("}\r\n") {
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// Every valid message is tagged with the string `message`. This means 3 things:
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// 1) We can discard everything before the first `message` (with `skip(1)`)
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// 2) We can split into separate messages by splitting on `message`
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// 3) We can use a regex that discards everything after the *first* valid
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// message (since the next message will have a new `message` tag)
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let messages = receiver.incoming_raw_msg.as_str().split("message").skip(1);
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let regex =
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Regex::new(r"timeline:(?P<timeline>.*?)\r\n\$\d+\r\n(?P<value>.*?)\r\n")
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.expect("Hard-codded");
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for message in messages {
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let timeline = regex.captures(message).expect("Hard-coded timeline regex")
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["timeline"]
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.to_string();
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let redis_msg: Value = serde_json::from_str(
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®ex.captures(message).expect("Hard-coded value regex")["value"],
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)
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.expect("Valid json");
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for msg_queue in receiver.msg_queues.values_mut() {
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if msg_queue.redis_channel == timeline {
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msg_queue.messages.push_back(redis_msg.clone());
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}
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}
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}
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// We've processed this raw msg and can safely discard it
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receiver.incoming_raw_msg.clear();
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}
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}
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}
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}
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impl<'a> Read for AsyncReadableStream<'a> {
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fn read(&mut self, buffer: &mut [u8]) -> Result<usize, std::io::Error> {
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self.0.read(buffer)
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}
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}
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impl<'a> AsyncRead for AsyncReadableStream<'a> {
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fn poll_read(&mut self, buf: &mut [u8]) -> Poll<usize, std::io::Error> {
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match self.read(buf) {
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Ok(t) => Ok(Async::Ready(t)),
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Err(_) => Ok(Async::NotReady),
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}
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}
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}
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