From e1dc982c5ffa2f996b0c3a4cfcd550e1af875749 Mon Sep 17 00:00:00 2001
From: Tobias Bieniek <tobias@bieniek.cloud>
Date: Fri, 3 Sep 2021 17:56:43 +0200
Subject: [PATCH] errors: Cast `PoolError::UnhealthyPool` into `503 Service
 Unavailable` error

---
 src/tests/unhealthy_database.rs | 23 +++++++++++++++++++++++
 src/util/errors.rs              | 10 ++++++++++
 2 files changed, 33 insertions(+)

diff --git a/src/tests/unhealthy_database.rs b/src/tests/unhealthy_database.rs
index 7a2b23ef89..a056378dfe 100644
--- a/src/tests/unhealthy_database.rs
+++ b/src/tests/unhealthy_database.rs
@@ -2,6 +2,7 @@ use crate::{
     builders::CrateBuilder,
     util::{MockAnonymousUser, RequestHelper, TestApp},
 };
+use http::StatusCode;
 use std::time::Duration;
 
 #[test]
@@ -64,3 +65,25 @@ fn assert_unconditional_redirects(anon: &MockAnonymousUser) {
     anon.get::<()>("/api/v1/crates/awesome-project/1.0.0/download")
         .assert_redirect_ends_with("/awesome-project/awesome-project-1.0.0.crate");
 }
+
+#[test]
+fn http_error_with_unhealthy_database() {
+    let (app, anon) = TestApp::init().with_slow_real_db_pool().empty();
+
+    let response = anon.get::<()>("/api/v1/summary");
+    assert_eq!(response.status(), StatusCode::OK);
+
+    app.db_chaosproxy().break_networking();
+
+    let response = anon.get::<()>("/api/v1/summary");
+    assert_eq!(response.status(), StatusCode::SERVICE_UNAVAILABLE);
+
+    app.db_chaosproxy().restore_networking();
+    app.as_inner()
+        .primary_database
+        .wait_until_healthy(Duration::from_millis(500))
+        .expect("the database did not return healthy");
+
+    let response = anon.get::<()>("/api/v1/summary");
+    assert_eq!(response.status(), StatusCode::OK);
+}
diff --git a/src/util/errors.rs b/src/util/errors.rs
index ce58357c4f..3d2cf72986 100644
--- a/src/util/errors.rs
+++ b/src/util/errors.rs
@@ -20,6 +20,7 @@ use std::fmt;
 use chrono::NaiveDateTime;
 use diesel::result::Error as DieselError;
 
+use crate::db::PoolError;
 use crate::util::AppResponse;
 
 mod json;
@@ -69,6 +70,11 @@ pub fn server_error<S: ToString + ?Sized>(error: &S) -> Box<dyn AppError> {
     Box::new(json::ServerError(error.to_string()))
 }
 
+/// Returns an error with status 503 and the provided description as JSON
+pub fn service_unavailable<S: ToString + ?Sized>(error: &S) -> Box<dyn AppError> {
+    Box::new(json::ServiceUnavailable(error.to_string()))
+}
+
 // =============================================================================
 // AppError trait
 
@@ -111,6 +117,10 @@ impl dyn AppError {
     }
 
     fn try_convert(err: &(dyn Error + Send + 'static)) -> Option<Box<Self>> {
+        if matches!(err.downcast_ref(), Some(PoolError::UnhealthyPool)) {
+            return Some(service_unavailable("Service unavailable"));
+        }
+
         match err.downcast_ref() {
             Some(DieselError::NotFound) => Some(not_found()),
             Some(DieselError::DatabaseError(_, info))