Extract db query into its own function.

src/routes/newsletters.rs

@@ -84,38 +84,45 @@ fn basic_authentication(headers: &HeaderMap) -> Result<Credentials, anyhow::Erro
     Ok(Credentials { username, password })
 }
 
-async fn validate_credentials(
+#[tracing::instrument(name = "Get stored credentials", skip(username, pool))]
-    credentials: Credentials,
+async fn get_stored_credentials(
+    username: &str,
     pool: &PgPool,
-) -> Result<uuid::Uuid, PublishError> {
+) -> Result<Option<(uuid::Uuid, String)>, anyhow::Error> {
-    let row: Option<_> = sqlx::query!(
+    let row = sqlx::query!(
         r#"
         SELECT user_id, password_hash
         FROM users
         WHERE username = $1
         "#,
-        credentials.username,
+        username,
     )
     .fetch_optional(pool)
     .await
-    .context("Failed to performed a query to retrieve stored credentials.")
+    .context("Failed to performed a query to retrieve stored credentials.")?
-    .map_err(PublishError::UnexpectedError)?;
+    .map(|row| (row.user_id, row.password_hash));
+    Ok(row)
+}
 
-    let (expected_password_hash, user_id) = match row {
+#[tracing::instrument(name = "Validate credentials", skip(credentials, pool))]
-        Some(row) => (row.password_hash, row.user_id),
+async fn validate_credentials(
-        None => {
+    credentials: Credentials,
-            return Err(PublishError::AuthError(anyhow::anyhow!(
+    pool: &PgPool,
-                "Unknown username."
+) -> Result<uuid::Uuid, PublishError> {
-            )))
+    let (user_id, expected_password_hash) = get_stored_credentials(&credentials.username, &pool)
-        }
+        .await
-    };
+        .map_err(PublishError::UnexpectedError)?
+        .ok_or_else(|| PublishError::AuthError(anyhow::anyhow!("Unknown username.")))?;
 
     let expected_password_hash = PasswordHash::new(&expected_password_hash)
         .context("Failed to parse hash in PHC string format.")
         .map_err(PublishError::UnexpectedError)?;
 
+    tracing::info_span!("Verify password hash")
+        .in_scope(|| {
             Argon2::default()
                 .verify_password(credentials.password.as_bytes(), &expected_password_hash)
+        })
         .context("Invalid password.")
         .map_err(PublishError::AuthError)?;