Update readme with execution diagram

.gitignore

@@ -2,3 +2,4 @@
 Cargo.lock
 docs/content/docs/CHANGELOG.md
 docs/content/docs/README.md
+.DS_Store

README.md

@@ -31,6 +31,25 @@ Here are some of the Backie's key features:
 - Task timeout: Tasks are retried if they are not completed in time
 - Scheduling of tasks: Tasks can be scheduled to be executed at a specific time
 
+## Task execution protocol
+
+The following diagram shows the protocol used to execute tasks:
+
+```mermaid
+stateDiagram-v2
+    [*] --> Ready
+    Ready --> Running: Task is picked up by a worker
+    Running --> Done: Task is finished
+    Running --> Failed: Task failed
+    Failed --> Ready: Task is retried
+    Failed --> [*]: Task is not retried anymore, max retries reached
+    Done --> [*]
+```
+
+When a task goes from `Running` to `Failed` it is retried. The number of retries is controlled by the
+[`BackgroundTask::MAX_RETRIES`] attribute. The default implementation uses `3` retries.
+
+
 ## Safety
 
 This crate uses `#![forbid(unsafe_code)]` to ensure everything is implemented in 100% safe Rust.

src/runnable.rs

@@ -53,8 +53,8 @@ pub trait BackgroundTask: Serialize + DeserializeOwned + Sync + Send + 'static {
 
     /// Number of retries for tasks.
     ///
-    /// By default, it is set to 5.
-    const MAX_RETRIES: i32 = 5;
+    /// By default, it is set to 3.
+    const MAX_RETRIES: i32 = 3;
 
     /// The application data provided to this task at runtime.
     type AppData: Clone + Send + 'static;