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it compiles, but theres something wrong with moves

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Bryan Stitt 2022-09-16 23:02:55 +00:00
parent 12b6d01434
commit 5cc4ca8d9e
2 changed files with 122 additions and 44 deletions
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135
deferred-rate-limiter/src/lib.rs
View File

@ -3,11 +3,12 @@ use moka::future::Cache;
use redis_rate_limiter::{RedisRateLimitResult, RedisRateLimiter};
use std::cell::Cell;
use std::cmp::Eq;
use std::fmt::Display;
use std::fmt::{Debug, Display};
use std::hash::Hash;
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::{atomic::AtomicU64, Arc};
use tokio::time::Instant;
use tracing::error;
/// A local cache that sits in front of a RedisRateLimiter
/// Generic accross the key so it is simple to use with IPs or user keys
@ -28,7 +29,7 @@ pub enum DeferredRateLimitResult {
impl<K> DeferredRateLimiter<K>
where
K: Copy + Display + Hash + Eq + Send + Sync + 'static,
K: Copy + Debug + Display + Hash + Eq + Send + Sync + 'static,
{
pub fn new(cache_size: u64, prefix: &str, rrl: RedisRateLimiter) -> Self {
Self {
@ -54,39 +55,55 @@ where
let arc_new_entry = Arc::new(AtomicBool::new(false));
let arc_retry_at = Arc::new(Cell::new(None));
let redis_key = format!("{}:{}", self.prefix, key);
// TODO: DO NOT UNWRAP HERE. figure out how to handle anyhow error being wrapped in an Arc
// TODO: i'm sure this could be a lot better. but race conditions make this hard to think through. brain needs sleep
let key_count = {
let arc_key_count: Arc<AtomicU64> = {
// clone things outside of the
let arc_new_entry = arc_new_entry.clone();
let arc_retry_at = arc_retry_at.clone();
let redis_key = redis_key.clone();
let rrl = Arc::new(self.rrl.clone());
self.local_cache
.try_get_with(*key, async move {
arc_new_entry.store(true, Ordering::Release);
self.local_cache.get_with(*key, async move { todo!() });
let label = format!("{}:{}", self.prefix, key);
/*
let x = self
.local_cache
.get_with(*key, move {
async move {
arc_new_entry.store(true, Ordering::Release);
let redis_count = match self
.rrl
.throttle_label(&label, Some(max_per_period), count)
.await?
{
RedisRateLimitResult::Allowed(count) => count,
RedisRateLimitResult::RetryAt(retry_at, count) => {
arc_retry_at.set(Some(retry_at));
count
}
RedisRateLimitResult::RetryNever => unimplemented!(),
};
// we do not use the try operator here because we want to be okay with redis errors
let redis_count = match rrl
.throttle_label(&redis_key, Some(max_per_period), count)
.await
{
Ok(RedisRateLimitResult::Allowed(count)) => count,
Ok(RedisRateLimitResult::RetryAt(retry_at, count)) => {
arc_retry_at.set(Some(retry_at));
count
}
Ok(RedisRateLimitResult::RetryNever) => unimplemented!(),
Err(x) => 0, // Err(err) => todo!("allow rate limit errors"),
// Err(RedisSomething)
// if we get a redis error, just let the user through. local caches will work fine
// though now that we do this, we need to reset rate limits every minute!
};
Ok::<_, anyhow::Error>(Arc::new(AtomicU64::new(redis_count)))
Arc::new(AtomicU64::new(redis_count))
}
})
.await
.unwrap()
.await;
*/
todo!("write more")
};
if arc_new_entry.load(Ordering::Acquire) {
// new entry
// new entry. redis was already incremented
// return the retry_at that we got from
if let Some(retry_at) = arc_retry_at.get() {
Ok(DeferredRateLimitResult::RetryAt(retry_at))
} else {
@ -94,24 +111,70 @@ where
}
} else {
// we have a cached amount here
let cached_key_count = arc_key_count.fetch_add(count, Ordering::Acquire);
// increment our local count if
// assuming no other parallel futures incremented this key, this is the count that redis has
let expected_key_count = cached_key_count + count;
let f = async move {
let label = format!("{}:{}", self.prefix, key);
if expected_key_count > max_per_period {
// rate limit overshot!
let now = self.rrl.now_as_secs();
let redis_count = match self
.rrl
.throttle_label(&label, Some(max_per_period), count)
.await?
{
RedisRateLimitResult::Allowed(count) => todo!("do something with allow"),
RedisRateLimitResult::RetryAt(retry_at, count) => todo!("do something with retry at")
RedisRateLimitResult::RetryNever => unimplemented!(),
// do not fetch_sub
// another row might have queued a redis throttle_label to keep our count accurate
// show that we are rate limited without even querying redis
let retry_at = self.rrl.next_period(now);
return Ok(DeferredRateLimitResult::RetryAt(retry_at));
} else {
// local caches think rate limit should be okay
// prepare a future to increment redis
let increment_redis_f = {
let rrl = self.rrl.clone();
async move {
let rate_limit_result = rrl
.throttle_label(&redis_key, Some(max_per_period), count)
.await?;
// TODO: log bad responses?
Ok::<_, anyhow::Error>(rate_limit_result)
}
};
Ok::<_, anyhow::Error>(())
};
// if close to max_per_period, wait for redis
// TODO: how close should we allow? depends on max expected concurent requests from one user
if expected_key_count > max_per_period * 98 / 100 {
// close to period. don't risk it. wait on redis
// match increment_redis_f.await {
// Ok(RedisRateLimitResult::Allowed(redis_count)) => todo!("1"),
// Ok(RedisRateLimitResult::RetryAt(retry_at, redis_count)) => todo!("2"),
// Ok(RedisRateLimitResult::RetryNever) => todo!("3"),
// Err(err) => {
// // don't let redis errors block our users!
// // error!(
// // // ?key, // TODO: this errors
// // ?err,
// // "unable to query rate limits. local cache available"
// // );
// todo!("4");
// }
// };
todo!("i think we can't move f around like this");
} else {
// rate limit has enough headroom that it should be safe to do this in the background
tokio::spawn(increment_redis_f);
}
}
let new_count = arc_key_count.fetch_add(count, Ordering::Release);
todo!("check new_count");
// increment our local count and check what happened
// THERE IS A SMALL RACE HERE, but thats the price we pay for speed. a few queries leaking through is okay
// if it becomes a problem, we can lock, but i don't love that. it might be short enough to be okay though
todo!("write more");
}

31
redis-rate-limiter/src/lib.rs
View File

@ -45,6 +45,25 @@ impl RedisRateLimiter {
}
}
pub fn now_as_secs(&self) -> f32 {
// TODO: if system time doesn't match redis, this won't work great
// TODO: now that we fixed
SystemTime::now()
.duration_since(UNIX_EPOCH)
.expect("cannot tell the time")
.as_secs_f32()
}
pub fn period_id(&self, now_as_secs: f32) -> f32 {
(now_as_secs / self.period) % self.period
}
pub fn next_period(&self, now_as_secs: f32) -> Instant {
let seconds_left_in_period = self.period - (now_as_secs % self.period);
Instant::now().add(Duration::from_secs_f32(seconds_left_in_period))
}
/// label might be an ip address or a user_key id.
/// if setting max_per_period, be sure to keep the period the same for all requests to this label
pub async fn throttle_label(
@ -59,13 +78,10 @@ impl RedisRateLimiter {
return Ok(RedisRateLimitResult::RetryNever);
}
let now = SystemTime::now()
.duration_since(UNIX_EPOCH)
.context("cannot tell the time")?
.as_secs_f32();
let now = self.now_as_secs();
// if self.period is 60, period_id will be the minute of the current time
let period_id = (now / self.period) % self.period;
let period_id = self.period_id(now);
// TODO: include max per period in the throttle key?
let throttle_key = format!("{}:{}:{}", self.key_prefix, label, period_id);
@ -91,9 +107,8 @@ impl RedisRateLimiter {
let new_count = *x.first().context("check rate limit result")?;
if new_count > max_per_period {
let seconds_left_in_period = self.period - (now % self.period);
let retry_at = Instant::now().add(Duration::from_secs_f32(seconds_left_in_period));
// TODO: this might actually be early if we are way over the count
let retry_at = self.next_period(now);
debug!(%label, ?retry_at, "rate limited: {}/{}", new_count, max_per_period);