Make worker queue size in dp configurable

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "teloxide"
 version = "0.7.2"
-edition = "2018"
+edition = "2021"
 description = "An elegant Telegram bots framework for Rust"
 repository = "https://github.com/teloxide/teloxide"
 documentation = "https://docs.rs/teloxide/"

src/dispatching/dispatcher.rs

@@ -32,6 +32,7 @@ pub struct DispatcherBuilder<R, Err> {
     handler: Arc<UpdateHandler<Err>>,
     default_handler: DefaultHandler,
     error_handler: Arc<dyn ErrorHandler<Err> + Send + Sync>,
+    worker_queue_size: usize,
 }
 
 impl<R, Err> DispatcherBuilder<R, Err>
@@ -75,6 +76,14 @@ where
         Self { dependencies, ..self }
     }
 
+    /// Specifies size of the queue for workers.
+    ///
+    /// By default it's 64.
+    #[must_use]
+    pub fn worker_queue_size(self, size: usize) -> Self {
+        Self { worker_queue_size: size, ..self }
+    }
+
     /// Constructs [`Dispatcher`].
     #[must_use]
     pub fn build(self) -> Dispatcher<R, Err> {
@@ -86,6 +95,7 @@ where
             error_handler: self.error_handler,
             allowed_updates: Default::default(),
             state: ShutdownToken::new(),
+            worker_queue_size: self.worker_queue_size,
             workers: HashMap::new(),
             default_worker: None,
         }
@@ -104,6 +114,7 @@ pub struct Dispatcher<R, Err> {
     handler: Arc<UpdateHandler<Err>>,
     default_handler: DefaultHandler,
 
+    worker_queue_size: usize,
     // Tokio TX channel parts associated with chat IDs that consume updates sequentially.
     workers: HashMap<ChatId, Worker>,
     // The default TX part that consume updates concurrently.
@@ -140,6 +151,8 @@ where
     where
         Err: Debug,
     {
+        const DEFAULT_WORKER_QUEUE_SIZE: usize = 64;
+
         DispatcherBuilder {
             bot,
             dependencies: DependencyMap::new(),
@@ -149,6 +162,7 @@ where
                 Box::pin(async {})
             }),
             error_handler: LoggingErrorHandler::new(),
+            worker_queue_size: DEFAULT_WORKER_QUEUE_SIZE,
         }
     }
 
@@ -270,10 +284,22 @@ where
 
                 let worker = match upd.chat() {
                     Some(chat) => self.workers.entry(chat.id).or_insert_with(|| {
-                        spawn_worker(deps, handler, default_handler, error_handler)
+                        spawn_worker(
+                            deps,
+                            handler,
+                            default_handler,
+                            error_handler,
+                            self.worker_queue_size,
+                        )
                     }),
                     None => self.default_worker.get_or_insert_with(|| {
-                        spawn_default_worker(deps, handler, default_handler, error_handler)
+                        spawn_default_worker(
+                            deps,
+                            handler,
+                            default_handler,
+                            error_handler,
+                            self.worker_queue_size,
+                        )
                     }),
                 };
 
@@ -316,18 +342,17 @@ where
     }
 }
 
-const WORKER_QUEUE_SIZE: usize = 64;
-
 fn spawn_worker<Err>(
     deps: DependencyMap,
     handler: Arc<UpdateHandler<Err>>,
     default_handler: DefaultHandler,
     error_handler: Arc<dyn ErrorHandler<Err> + Send + Sync>,
+    queue_size: usize,
 ) -> Worker
 where
     Err: Send + Sync + 'static,
 {
-    let (tx, rx) = tokio::sync::mpsc::channel(WORKER_QUEUE_SIZE);
+    let (tx, rx) = tokio::sync::mpsc::channel(queue_size);
 
     let deps = Arc::new(deps);
 
@@ -348,11 +373,12 @@ fn spawn_default_worker<Err>(
     handler: Arc<UpdateHandler<Err>>,
     default_handler: DefaultHandler,
     error_handler: Arc<dyn ErrorHandler<Err> + Send + Sync>,
+    queue_size: usize,
 ) -> Worker
 where
     Err: Send + Sync + 'static,
 {
-    let (tx, rx) = tokio::sync::mpsc::channel(WORKER_QUEUE_SIZE);
+    let (tx, rx) = tokio::sync::mpsc::channel(queue_size);
 
     let deps = Arc::new(deps);