Add configuration for the write lock the cache is using to update (#415)

2 files changed, 75 insertions, 2 deletions

diff --git a/src/cache/mod.rs b/src/cache/mod.rs
index 780c364..f02d1c6 100644
--- a/src/cache/mod.rs
+++ b/src/cache/mod.rs
@@ -52,7 +52,8 @@ use std::collections::{
 };
 use std::{
     default::Default,
-    sync::Arc
+    sync::Arc,
+    time::Duration,
 };
 
 mod cache_update;
@@ -756,6 +757,15 @@ impl Cache {
         e.update(self)
     }
 
+    /// Gets the duration it will try for when acquiring a write lock.
+    ///
+    /// Refer to the documentation for [`cache_lock_time`] for more information.
+    ///
+    /// [`cache_lock_time`]: struct.Settings.html#method.cache_lock_time
+    pub fn get_try_write_duration(&self) -> Option<Duration> {
+        self.settings.cache_lock_time
+    }
+
     pub(crate) fn update_user_entry(&mut self, user: &User) {
         match self.users.entry(user.id) {
             Entry::Vacant(e) => {
diff --git a/src/cache/settings.rs b/src/cache/settings.rs
index 51bff4c..975ddc6 100644
--- a/src/cache/settings.rs
+++ b/src/cache/settings.rs
@@ -1,3 +1,5 @@
+use std::time::Duration;
+
 /// Settings for the cache.
 ///
 /// # Examples
@@ -10,15 +12,34 @@
 /// let mut settings = CacheSettings::new();
 /// settings.max_messages(10);
 /// ```
-#[derive(Clone, Debug, Default)]
+#[derive(Clone, Debug)]
 pub struct Settings {
     /// The maximum number of messages to store in a channel's message cache.
     ///
     /// Defaults to 0.
     pub max_messages: usize,
+
+    /// The Duration cache updates will try to acquire write-locks for.
+    ///
+    /// Defaults to 10 milliseconds.
+    ///
+    /// **Note**:
+    /// If set to `None`, cache updates will acquire write-lock until available,
+    /// potentially deadlocking.
+    pub cache_lock_time: Option<Duration>,
     __nonexhaustive: (),
 }
 
+impl Default for Settings {
+    fn default() -> Self {
+        Settings {
+            max_messages: usize::default(),
+            cache_lock_time: Some(Duration::from_millis(10)),
+            __nonexhaustive: (),
+        }
+    }
+}
+
 impl Settings {
     /// Creates new settings to be used with a cache.
     #[inline]
@@ -47,4 +68,46 @@ impl Settings {
 
         self
     }
+
+    /// Sets the duration that the cache will try to aquire a write lock.
+    ///
+    /// Refer to [`cache_lock_time`] for more information.
+    ///
+    /// **Note**:
+    /// Should be set before the client gets started, as it can not be
+    /// changed after the first read of the duration.
+    ///
+    /// # Examples
+    ///
+    /// Set the time that it will try to aquire a lock.
+    ///
+    /// ```rust,no_run
+    /// use std::time::Duration;
+    /// use std::env;
+    /// use serenity::prelude::*;
+    ///
+    /// struct Handler;
+    ///
+    /// impl EventHandler for Handler {}
+    ///
+    /// fn main() {
+    ///     let token = env::var("DISCORD_TOKEN")
+    ///        .expect("Expected a token in the environment");
+    ///     serenity::CACHE
+    ///        .write().settings_mut()
+    ///        .cache_lock_time(Some(Duration::from_secs(1)));
+    ///     let mut client = Client::new(&token, Handler).unwrap();
+    ///
+    ///     if let Err(why) = client.start() {
+    ///        println!("Client error: {:?}", why);
+    ///     }
+    /// }
+    /// ```
+    ///
+    /// [`cache_lock_time`]: #structfield.cache_lock_time
+    pub fn cache_lock_time(&mut self, duration: Option<Duration>) -> &mut Self {
+        self.cache_lock_time = duration;
+
+        self
+    }
 }