From ad0c5410d73d607f6aa70758ea15e80774f8534e Mon Sep 17 00:00:00 2001
From: Konstantin Knizhnik <knizhnik@garret.ru>
Date: Sat, 29 Oct 2022 22:49:57 +0300
Subject: [PATCH] Limit number of buffered responses

---
 pageserver/src/page_service.rs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/pageserver/src/page_service.rs b/pageserver/src/page_service.rs
index d139c9dedd..985026b2ac 100644
--- a/pageserver/src/page_service.rs
+++ b/pageserver/src/page_service.rs
@@ -275,6 +275,7 @@ impl PageServerHandler {
         pgb.flush().await?;
 
         let metrics = PageRequestMetrics::new(&tenant_id, &timeline_id);
+        let mut n_buffered_responses = 0usize;
 
         loop {
             let msg = tokio::select! {
@@ -312,7 +313,7 @@ impl PageServerHandler {
                 }
                 PagestreamFeMessage::GetPage(req) => {
                     let _timer = metrics.get_page_at_lsn.start_timer();
-                    do_flush = !req.prefetch;
+                    do_flush = !req.prefetch || n_buffered_responses > MAX_BUFFERED_RESPONSES;
                     self.handle_get_page_at_lsn_request(&timeline, &req).await
                 }
                 PagestreamFeMessage::DbSize(req) => {
@@ -331,8 +332,10 @@ impl PageServerHandler {
             });
 
             pgb.write_message(&BeMessage::CopyData(&response.serialize()))?;
+            n_buffered_responses += 1;
             if do_flush {
                 pgb.flush().await?;
+                n_buffered_responses = 0;
             }
         }
         Ok(())