Change queue order to "first come first served"

.gitignore

@@ -4,4 +4,5 @@ target
 /cache/
 /rust.git/
 /rust/
-/results
+/results
+/.idea/

site/src/job_queue/mod.rs

@@ -15,6 +15,7 @@ use database::{
     PendingBenchmarkRequests, Profile, QueuedCommit, Target,
 };
 use parking_lot::RwLock;
+use std::cmp::Reverse;
 use std::sync::Arc;
 use std::time::Instant;
 use tokio::time::{self, Duration, MissedTickBehavior};
@@ -154,12 +155,11 @@ fn sort_benchmark_requests(pending: PendingBenchmarkRequests) -> Vec<BenchmarkRe
         level.sort_unstable_by_key(|bmr| {
             (
                 // Higher priority requests go first
-                -bmr.priority(),
-                // PR number takes priority
-                bmr.pr().unwrap_or(0),
+                Reverse(bmr.priority()),
+                // Older requests take priority
+                bmr.created_at(),
                 // Order master commits before try commits
                 if bmr.is_master() { 0 } else { 1 },
-                bmr.created_at(),
             )
         });
         for c in level {
@@ -900,6 +900,35 @@ mod tests {
         .await;
     }
 
+    #[tokio::test]
+    async fn queue_oldest_request_first() {
+        run_postgres_test(|ctx| async {
+            ctx.add_collector(CollectorBuilder::default()).await;
+
+            ctx.insert_master_request("base", "base2", 1).await;
+            ctx.insert_try_request(4, 0).await;
+            ctx.db()
+                .attach_shas_to_try_benchmark_request(4, "pr4", "base", Utc::now())
+                .await
+                .unwrap();
+            ctx.insert_try_request(2, 0).await;
+            ctx.db()
+                .attach_shas_to_try_benchmark_request(2, "pr2", "base", Utc::now())
+                .await
+                .unwrap();
+            ctx.insert_try_request(3, 0).await;
+            ctx.db()
+                .attach_shas_to_try_benchmark_request(3, "pr3", "base", Utc::now())
+                .await
+                .unwrap();
+
+            let queue = build_queue(ctx.db()).await?;
+            queue_order_matches(&queue, &["base", "pr4", "pr2", "pr3"]);
+            Ok(ctx)
+        })
+        .await;
+    }
+
     #[tokio::test]
     async fn insert_all_jobs() {
         run_postgres_test(|mut ctx| async {