feat: add exponential backoff with jitter in the worker loop retrials

Cargo.toml

@@ -37,6 +37,7 @@ htmlescape = "0.3.1"
 actix-web-flash-messages = { version = "0.4", features = ["cookies"] }
 actix-session = { version = "0.9", features = ["redis-rs-tls-session"] }
 serde_json = "1.0"
+exponential-backoff = "1.2.0"
 
 [dependencies.reqwest]
 version = "0.12"

README.md

@@ -29,7 +29,7 @@ Add these validation checks to our POST /admin/password endpoint.
 
 ### Section 11
 - [ ] There is no retry if the email delivery attempt fails. We could enhance this by adding a `n_retries` and `execute_after` columns to keep track of how many attemps have already taken place and when the next attempt should be executed.
-- [ ] Add an exponential backoff with jitter in the `issue_delivery_worker::worker_loop` function.
+- [X] Add an exponential backoff with jitter in the `issue_delivery_worker::worker_loop` function.
 - [ ] Add an expiry mechanism for the idempotency keys using background workers as reference.
 
 ## Troubleshooting

src/idempotency/persistence.rs

@@ -59,10 +59,7 @@ pub async fn save_response(
     http_response: HttpResponse,
 ) -> Result<HttpResponse, anyhow::Error> {
     let (response_head, body) = http_response.into_parts();
-    let body = to_bytes(body)
-        .await
-        .map_err(|e| anyhow::anyhow!("{}", e))?
-    ;
+    let body = to_bytes(body).await.map_err(|e| anyhow::anyhow!("{}", e))?;
     let status_code = response_head.status().as_u16() as i16;
     let headers = {
         let mut h = Vec::with_capacity(response_head.headers().len());

src/issue_delivery_worker.rs

@@ -1,7 +1,9 @@
 use crate::domain::SubscriberEmail;
 use crate::email_client::EmailClient;
 use crate::{configuration::Settings, startup::get_connection_pool};
+use exponential_backoff::Backoff;
 use sqlx::{Executor, PgPool, Postgres, Transaction};
+use std::ops::Add;
 use std::time::Duration;
 use tracing::{field::display, Span};
 use uuid::Uuid;
@@ -34,16 +36,30 @@ async fn get_issue(pool: &PgPool, issue_id: Uuid) -> Result<NewsletterIssue, any
     Ok(issue)
 }
 
+fn get_backoff() -> Backoff {
+    let retries = 8;
+    let min = Duration::from_secs(1);
+    let max = Duration::from_secs(60);
+    let mut backoff = Backoff::new(retries, min, max);
+    backoff.set_jitter(0.25);
+    backoff
+}
+
 async fn worker_loop(pool: PgPool, email_client: EmailClient) -> Result<(), anyhow::Error> {
+    let backoff = get_backoff();
     loop {
-        match try_execute_task(&pool, &email_client).await {
-            Ok(ExecutionOutcome::EmptyQueue) => {
-                tokio::time::sleep(Duration::from_secs(10)).await;
-            }
-            Err(_) => {
-                tokio::time::sleep(Duration::from_secs(1)).await;
+        for duration in &backoff {
+            match try_execute_task(&pool, &email_client).await {
+                Ok(ExecutionOutcome::EmptyQueue) => {
+                    tokio::time::sleep(duration.add(Duration::from_secs(10))).await;
+                }
+                Err(_) => {
+                    tokio::time::sleep(duration).await;
+                }
+                Ok(ExecutionOutcome::TaskCompleted) => {
+                    break;
+                }
             }
-            Ok(ExecutionOutcome::TaskCompleted) => {}
         }
     }
 }