Use read-only replica pool for download count endpoints

Author: jtgeibel

src/controllers/krate/downloads.rs

@@ -19,7 +19,7 @@ pub fn downloads(req: &mut dyn Request) -> AppResult<Response> {
     use diesel::sql_types::BigInt;
 
     let crate_name = &req.params()["crate_id"];
-    let conn = req.db_conn()?;
+    let conn = req.db_read_only()?;
     let krate = Crate::by_name(crate_name).first::<Crate>(&*conn)?;
 
     let mut versions = krate.all_versions().load::<Version>(&*conn)?;

src/controllers/version/downloads.rs

@@ -70,7 +70,7 @@ fn increment_download_counts(
 /// Handles the `GET /crates/:crate_id/:version/downloads` route.
 pub fn downloads(req: &mut dyn Request) -> AppResult<Response> {
     let (version, _) = version_and_crate(req)?;
-    let conn = req.db_conn()?;
+    let conn = req.db_read_only()?;
     let cutoff_end_date = req
         .query()
         .get("before_date")