[rate-limiter] &mut not required for RateLimiter (#7)

`dashmap` already handles mut concurrency, and we don't perform any other mutation on theRateLimiter` itself during these function call    s.

#6

README.md

@@ -39,7 +39,7 @@ use gcra::{GcraError, RateLimit, RateLimiter};
 #[tokio::main]
 async fn main() -> Result<(), GcraError> {
     let rate_limit = RateLimit::per_sec(2);
-    let mut rl = RateLimiter::new(4);
+    let rl = RateLimiter::new(4);
 
     rl.check("key", rate_limit.clone(), 1).await?;
     rl.check("key", rate_limit.clone(), 1).await?;

examples/rate_limiter.rs

@@ -6,7 +6,7 @@ const WORKER_SHARD_COUNT: usize = 2;
 #[tokio::main]
 async fn main() -> Result<(), GcraError> {
     let rate_limit = RateLimit::per_sec(2);
-    let mut rl = RateLimiter::with_shards(CACHE_CAPACITY, WORKER_SHARD_COUNT);
+    let rl = RateLimiter::with_shards(CACHE_CAPACITY, WORKER_SHARD_COUNT);
 
     rl.check("key", rate_limit.clone(), 1).await?;
     rl.check("key", rate_limit.clone(), 1).await?;

src/lib.rs

@@ -35,7 +35,7 @@
 //! #[tokio::main]
 //! async fn main() -> Result<(), GcraError> {
 //!     let rate_limit = RateLimit::per_sec(2);
-//!     let mut rl = RateLimiter::new(4);
+//!     let rl = RateLimiter::new(4);
 //!
 //!     rl.check("key", rate_limit.clone(), 1).await?;
 //!     rl.check("key", rate_limit.clone(), 1).await?;

src/rate_limiter/rate_limiter.rs

@@ -80,7 +80,7 @@ where
     /// - [GcraError::DeniedIndefinitely] if the request can never succeed
     #[inline]
     pub async fn check(
-        &mut self,
+        &self,
         key: Key,
         rate_limit: RateLimit,
         cost: u32,
@@ -94,7 +94,7 @@ where
     /// - [GcraError::DeniedUntil] if the request can succeed after the [Instant] returned.
     /// - [GcraError::DeniedIndefinitely] if the request can never succeed
     pub async fn check_at(
-        &mut self,
+        &self,
         key: Key,
         rate_limit: RateLimit,
         cost: u32,
@@ -122,7 +122,7 @@ where
     }
 
     /// Removes entries that have expired
-    pub fn prune_expired(&mut self) {
+    pub fn prune_expired(&self) {
         let now = self.clock.now();
 
         self.map.retain(|_key, entry| match entry.expires_at {
@@ -143,7 +143,7 @@ mod tests {
     #[tokio::test]
     async fn rate_limiter_run_until_denied() {
         let rate_limit = RateLimit::new(3, Duration::from_secs(3));
-        let mut rl = RateLimiter::with_shards(4, 2);
+        let rl = RateLimiter::with_shards(4, 2);
 
         for _ in 0..rate_limit.resource_limit {
             assert!(
@@ -164,7 +164,7 @@ mod tests {
     #[tokio::test]
     async fn rate_limiter_indefinitly_denied() {
         let rate_limit = RateLimit::new(3, Duration::from_secs(3));
-        let mut rl = RateLimiter::with_shards(4, 2);
+        let rl = RateLimiter::with_shards(4, 2);
 
         match rl.check("key", rate_limit.clone(), 9).await {
             Ok(_) => panic!("We should be rate limited"),
@@ -182,7 +182,7 @@ mod tests {
     #[tokio::test]
     async fn rate_limiter_leaks() {
         let rate_limit = RateLimit::per_sec(2);
-        let mut rl = RateLimiter::with_shards(4, 2);
+        let rl = RateLimiter::with_shards(4, 2);
 
         let now = Instant::now();
         assert!(rl.check_at("key", rate_limit.clone(), 1, now).await.is_ok());
@@ -237,7 +237,7 @@ mod tests {
         let clock = FakeClock::new();
 
         let rate_limit = RateLimit::per_sec(3);
-        let mut rl: RateLimiter<_, _, FxBuildHasher> = RateLimiter::with_clock(clock.clone());
+        let rl: RateLimiter<_, _, FxBuildHasher> = RateLimiter::with_clock(clock.clone());
 
         for index in 0..rate_limit.resource_limit {
             assert!(