From d8c649b3cd1bdd6a0be8f2525ca8a9376aa143bd Mon Sep 17 00:00:00 2001
From: bwbonanno <bradfordbonanno@gmail.com>
Date: Wed, 18 Oct 2023 08:28:24 -0700
Subject: [PATCH] Return recoverable error if we fail to retrieve metrics state

---
 index-scheduler/src/error.rs  |  4 ++++
 meilisearch/src/middleware.rs | 23 +++++++++++++++--------
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/index-scheduler/src/error.rs b/index-scheduler/src/error.rs
index ddc6960f7..417a55be8 100644
--- a/index-scheduler/src/error.rs
+++ b/index-scheduler/src/error.rs
@@ -113,6 +113,8 @@ pub enum Error {
     Dump(#[from] dump::Error),
     #[error(transparent)]
     Heed(#[from] heed::Error),
+    #[error("Unable to record metrics for request.")]
+    CannotRecordMetrics,
     #[error(transparent)]
     Milli(#[from] milli::Error),
     #[error("An unexpected crash occurred when processing the task.")]
@@ -177,6 +179,7 @@ impl Error {
             | Error::TaskCancelationWithEmptyQuery
             | Error::Dump(_)
             | Error::Heed(_)
+            | Error::CannotRecordMetrics
             | Error::Milli(_)
             | Error::ProcessBatchPanicked
             | Error::FileStore(_)
@@ -223,6 +226,7 @@ impl ErrorCode for Error {
             Error::Milli(e) => e.error_code(),
             Error::ProcessBatchPanicked => Code::Internal,
             Error::Heed(e) => e.error_code(),
+            Error::CannotRecordMetrics => Code::Internal,
             Error::HeedTransaction(e) => e.error_code(),
             Error::FileStore(e) => e.error_code(),
             Error::IoError(e) => e.error_code(),
diff --git a/meilisearch/src/middleware.rs b/meilisearch/src/middleware.rs
index de74b3a37..7f7429186 100644
--- a/meilisearch/src/middleware.rs
+++ b/meilisearch/src/middleware.rs
@@ -6,7 +6,9 @@ use actix_web::dev::{self, Service, ServiceRequest, ServiceResponse, Transform};
 use actix_web::web::Data;
 use actix_web::Error;
 use futures_util::future::LocalBoxFuture;
+use index_scheduler::Error::CannotRecordMetrics;
 use index_scheduler::IndexScheduler;
+use meilisearch_types::error::ResponseError;
 use prometheus::HistogramTimer;
 
 pub struct RouteMetrics;
@@ -49,15 +51,20 @@ where
 
     fn call(&self, req: ServiceRequest) -> Self::Future {
         let mut histogram_timer: Option<HistogramTimer> = None;
-        let data = req.app_data::<Data<IndexScheduler>>();
-        let metrics_enabled = data
-            .ok_or("Could not get index scheduler")
-            .and_then(|index_scheduler| {
-                index_scheduler.features().map_err(|_| "Could not get features")
-            })
-            .and_then(|features| features.check_metrics().map_err(|_| "Metrics not enabled"));
 
-        if let Ok(()) = metrics_enabled {
+        // calling unwrap here is safe because index scheduler is added to app data while creating actix app.
+        // also, the tests will fail if this is not present.
+        let index_scheduler = req.app_data::<Data<IndexScheduler>>().unwrap();
+        let features = match index_scheduler.features() {
+            Ok(features) => features,
+            Err(_e) => {
+                return Box::pin(
+                    async move { Err(ResponseError::from(CannotRecordMetrics).into()) },
+                );
+            }
+        };
+
+        if features.check_metrics().is_ok() {
             let request_path = req.path();
             let is_registered_resource = req.resource_map().has_resource(request_path);
             if is_registered_resource {