1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136

pub mod error;

mod bucket;
mod headers;

pub use self::{
    error::{RatelimitError, RatelimitResult},
    headers::RatelimitHeaders,
};

use self::bucket::{Bucket, BucketQueueTask, TimeRemaining};
use crate::routing::Path;
use std::{
    collections::hash_map::{Entry, HashMap},
    sync::{
        atomic::{AtomicBool, Ordering},
        Arc, Mutex,
    },
    time::Duration,
};
use tokio::sync::{
    oneshot::{self, Receiver, Sender},
    Mutex as AsyncMutex,
};

/// Global lock. We use a pair to avoid actually locking the mutex every check.
/// This allows futures to only wait on the global lock when a global ratelimit
/// is in place by, in turn, waiting for a guard, and then each immediately
/// dropping it.
#[derive(Debug, Default)]
struct GlobalLockPair(AsyncMutex<()>, AtomicBool);

impl GlobalLockPair {
    pub fn lock(&self) {
        self.1.store(true, Ordering::Release);
    }

    pub fn unlock(&self) {
        self.1.store(false, Ordering::Release);
    }

    pub fn is_locked(&self) -> bool {
        self.1.load(Ordering::Relaxed)
    }
}

#[derive(Clone, Debug, Default)]
pub struct Ratelimiter {
    buckets: Arc<Mutex<HashMap<Path, Arc<Bucket>>>>,
    global: Arc<GlobalLockPair>,
}

impl Ratelimiter {
    /// Create a new ratelimiter.
    ///
    /// Most users won't need to use this directly. If you're creating your own
    /// HTTP proxy then this is good to use for your own ratelimiting.
    pub fn new() -> Self {
        Self::default()
    }

    #[deprecated(since = "0.5.0", note = "use `ticket` instead, which is not async")]
    pub async fn get(&self, path: Path) -> Receiver<Sender<Option<RatelimitHeaders>>> {
        self.ticket(path)
    }

    pub fn ticket(&self, path: Path) -> Receiver<Sender<Option<RatelimitHeaders>>> {
        #[cfg(feature = "tracing")]
        tracing::debug!("getting bucket for path: {:?}", path);

        let (tx, rx) = oneshot::channel();
        let (bucket, fresh) = self.entry(path.clone(), tx);

        if fresh {
            tokio::spawn(
                BucketQueueTask::new(
                    bucket,
                    Arc::clone(&self.buckets),
                    Arc::clone(&self.global),
                    path,
                )
                .run(),
            );
        }

        rx
    }

    /// Provide an estimate for the time left until a path can be used
    /// without being ratelimited.
    ///
    /// This method is not guaranteed to be accurate and may return
    /// None if either no ratelimit is known or buckets are remaining.
    pub async fn time_until_available(&self, path: &Path) -> Option<Duration> {
        let buckets = self.buckets.lock().expect("ratelimit buckets poisoned");

        match buckets.get(path)?.time_remaining() {
            TimeRemaining::Finished | TimeRemaining::NotStarted => None,
            TimeRemaining::Some(duration) => Some(duration),
        }
    }

    fn entry(
        &self,
        path: Path,
        tx: Sender<Sender<Option<RatelimitHeaders>>>,
    ) -> (Arc<Bucket>, bool) {
        // nb: not realisically point of contention
        let mut buckets = self.buckets.lock().expect("ratelimit buckets poisoned");

        match buckets.entry(path.clone()) {
            Entry::Occupied(bucket) => {
                #[cfg(feature = "tracing")]
                tracing::debug!("got existing bucket: {:?}", path);

                let bucket = bucket.into_mut();
                bucket.queue.push(tx);
                #[cfg(feature = "tracing")]
                tracing::debug!("added request into bucket queue: {:?}", path);

                (Arc::clone(bucket), false)
            }
            Entry::Vacant(entry) => {
                #[cfg(feature = "tracing")]
                tracing::debug!("making new bucket for path: {:?}", path);
                let bucket = Bucket::new(path);
                bucket.queue.push(tx);

                let bucket = Arc::new(bucket);
                entry.insert(Arc::clone(&bucket));

                (bucket, true)
            }
        }
    }
}