flodgatt/src/redis_to_client_stream/receiver/mod.rs

//! Receives data from Redis, sorts it by `ClientAgent`, and stores it until
//! polled by the correct `ClientAgent`.  Also manages sububscriptions and
//! unsubscriptions to/from Redis.
mod err;
mod message_queues;

pub use err::ReceiverErr;
pub use message_queues::{MessageQueues, MsgQueue};

use super::redis::{redis_connection::RedisCmd, RedisConn};

use crate::{
    config,
    messages::Event,
    parse_client_request::{Stream, Subscription, Timeline},
};

use {
    futures::{Async, Poll},
    hashbrown::HashMap,
    uuid::Uuid,
};

use std::{
    result,
    sync::{Arc, Mutex},
    time::{Duration, Instant},
};

type Result<T> = result::Result<T, ReceiverErr>;

/// The item that streams from Redis and is polled by the `ClientAgent`
#[derive(Debug)]
pub struct Receiver {
    redis_connection: RedisConn,
    redis_poll_interval: Duration,
    redis_polled_at: Instant,
    pub msg_queues: MessageQueues,
    clients_per_timeline: HashMap<Timeline, i32>,
}

impl Receiver {
    /// Create a new `Receiver`, with its own Redis connections (but, as yet, no
    /// active subscriptions).
    pub fn try_from(redis_cfg: config::RedisConfig) -> Result<Self> {
        let redis_poll_interval = *redis_cfg.polling_interval;
        let redis_connection = RedisConn::new(redis_cfg)?;

        Ok(Self {
            redis_polled_at: Instant::now(),
            redis_poll_interval,
            redis_connection,
            msg_queues: MessageQueues(HashMap::new()),
            clients_per_timeline: HashMap::new(),
        })
    }

    pub fn into_arc(self) -> Arc<Mutex<Self>> {
        Arc::new(Mutex::new(self))
    }

    /// Assigns the `Receiver` a new timeline to monitor and runs other
    /// first-time setup.
    pub fn add_subscription(&mut self, subscription: &Subscription) -> Result<()> {
        let (tag, tl) = (subscription.hashtag_name.clone(), subscription.timeline);

        if let (Some(hashtag), Timeline(Stream::Hashtag(id), _, _)) = (tag, tl) {
            self.redis_connection.update_cache(hashtag, id);
        };
        self.msg_queues.insert(subscription.id, MsgQueue::new(tl));

        let number_of_subscriptions = self
            .clients_per_timeline
            .entry(tl)
            .and_modify(|n| *n += 1)
            .or_insert(1);

        use RedisCmd::*;
        if *number_of_subscriptions == 1 {
            self.redis_connection.send_cmd(Subscribe, &tl)?
        };

        Ok(())
    }

    pub fn remove_subscription(&mut self, subscription: &Subscription) -> Result<()> {
        let tl = subscription.timeline;
        self.msg_queues.remove(&subscription.id);
        let number_of_subscriptions = self
            .clients_per_timeline
            .entry(tl)
            .and_modify(|n| *n -= 1)
            .or_insert_with(|| {
                log::error!(
                    "Attempted to unsubscribe from a timeline to which you were not subscribed: {:?}",
                    tl
                );
                0
            });
        use RedisCmd::*;
        if *number_of_subscriptions == 0 {
            self.redis_connection.send_cmd(Unsubscribe, &tl)?;
            self.clients_per_timeline.remove_entry(&tl);
        };

        Ok(())
    }

    /// Returns the oldest message in the `ClientAgent`'s queue (if any).
    ///
    /// Note: This method does **not** poll Redis every time, because polling
    /// Redis is significantly more time consuming that simply returning the
    /// message already in a queue.  Thus, we only poll Redis if it has not
    /// been polled lately.
    pub fn poll_for(&mut self, id: Uuid) -> Poll<Option<Event>, ReceiverErr> {
        //        let (t1, mut polled_redis) = (Instant::now(), false);
        if self.redis_polled_at.elapsed() > self.redis_poll_interval {
            loop {
                match self.redis_connection.poll_redis() {
                    Ok(Async::NotReady) => break,
                    Ok(Async::Ready(Some((timeline, event)))) => {
                        self.msg_queues
                            .values_mut()
                            .filter(|msg_queue| msg_queue.timeline == timeline)
                            .for_each(|msg_queue| {
                                msg_queue.messages.push_back(event.clone());
                            });
                    }
                    Ok(Async::Ready(None)) => (), // subscription cmd or msg for other namespace
                    Err(err) => Err(err)?,
                }
            }
            //          polled_redis = true;
            self.redis_polled_at = Instant::now();
        }

        // If the `msg_queue` being polled has any new messages, return the first (oldest) one
        let msg_q = self.msg_queues.get_mut(&id).ok_or(ReceiverErr::InvalidId)?;
        let res = match msg_q.messages.pop_front() {
            Some(event) => Ok(Async::Ready(Some(event))),
            None => Ok(Async::NotReady),
        };
        // if !polled_redis {
        //     log::info!("poll_for in {:?}", t1.elapsed());
        // }
        res
    }

    pub fn count_connections(&self) -> String {
        format!(
            "Current connections: {}",
            self.clients_per_timeline.values().sum::<i32>()
        )
    }

    pub fn list_connections(&self) -> String {
        let max_len = self
            .clients_per_timeline
            .keys()
            .fold(0, |acc, el| acc.max(format!("{:?}:", el).len()));
        self.clients_per_timeline
            .iter()
            .map(|(tl, n)| {
                let tl_txt = format!("{:?}:", tl);
                format!("{:>1$} {2}\n", tl_txt, max_len, n)
            })
            .collect()
    }

    pub fn queue_length(&self) -> String {
        format!(
            "Longest MessageQueue: {}",
            self.msg_queues
                .0
                .values()
                .fold(0, |acc, el| acc.max(el.messages.len()))
        )
    }
}