From 7963237c431fee95c4e3c696a9ce6c63740db355 Mon Sep 17 00:00:00 2001
From: Joonas Koivunen <joonas@neon.tech>
Date: Tue, 30 May 2023 14:30:16 +0300
Subject: [PATCH] to be dropped: mandatory PAGESERVER_THREADS_PER_RUNTIME

---
 control_plane/src/background_process.rs |  7 ++++++-
 pageserver/src/task_mgr.rs              | 17 +++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/control_plane/src/background_process.rs b/control_plane/src/background_process.rs
index 1f3f8f45ea..f1c24b35aa 100644
--- a/control_plane/src/background_process.rs
+++ b/control_plane/src/background_process.rs
@@ -219,7 +219,12 @@ fn fill_rust_env_vars(cmd: &mut Command) -> &mut Command {
     let mut filled_cmd = cmd.env_clear().env("RUST_BACKTRACE", backtrace_setting);
 
     // Pass through these environment variables to the command
-    for var in ["LLVM_PROFILE_FILE", "FAILPOINTS", "RUST_LOG"] {
+    for var in [
+        "LLVM_PROFILE_FILE",
+        "FAILPOINTS",
+        "RUST_LOG",
+        "PAGESERVER_THREADS_PER_RUNTIME",
+    ] {
         if let Some(val) = std::env::var_os(var) {
             filled_cmd = filled_cmd.env(var, val);
         }
diff --git a/pageserver/src/task_mgr.rs b/pageserver/src/task_mgr.rs
index b58f51665c..c8a505faf2 100644
--- a/pageserver/src/task_mgr.rs
+++ b/pageserver/src/task_mgr.rs
@@ -103,9 +103,23 @@ use crate::shutdown_pageserver;
 // other operations, if the upload tasks e.g. get blocked on locks. It shouldn't
 // happen, but still.
 //
+
+pub static THREADS_PER_RUNTIME: Lazy<std::num::NonZeroUsize> = Lazy::new(|| {
+    let num = std::env::var_os("PAGESERVER_THREADS_PER_RUNTIME")
+        .and_then(|var| var.to_str().map(|v| v.parse::<usize>()))
+        .expect("PAGESERVER_THREADS_PER_RUNTIME is unset")
+        .expect("PAGESERVER_THREADS_PER_RUNTIME is not an usize");
+
+    let num =
+        std::num::NonZeroUsize::new(num).expect("PAGESERVER_THREADS_PER_RUNTIME out of range");
+
+    num
+});
+
 pub static COMPUTE_REQUEST_RUNTIME: Lazy<Runtime> = Lazy::new(|| {
     tokio::runtime::Builder::new_multi_thread()
         .thread_name("compute request worker")
+        .worker_threads(THREADS_PER_RUNTIME.get())
         .enable_all()
         .build()
         .expect("Failed to create compute request runtime")
@@ -114,6 +128,7 @@ pub static COMPUTE_REQUEST_RUNTIME: Lazy<Runtime> = Lazy::new(|| {
 pub static MGMT_REQUEST_RUNTIME: Lazy<Runtime> = Lazy::new(|| {
     tokio::runtime::Builder::new_multi_thread()
         .thread_name("mgmt request worker")
+        .worker_threads(THREADS_PER_RUNTIME.get())
         .enable_all()
         .build()
         .expect("Failed to create mgmt request runtime")
@@ -122,6 +137,7 @@ pub static MGMT_REQUEST_RUNTIME: Lazy<Runtime> = Lazy::new(|| {
 pub static WALRECEIVER_RUNTIME: Lazy<Runtime> = Lazy::new(|| {
     tokio::runtime::Builder::new_multi_thread()
         .thread_name("walreceiver worker")
+        .worker_threads(THREADS_PER_RUNTIME.get())
         .enable_all()
         .build()
         .expect("Failed to create walreceiver runtime")
@@ -130,6 +146,7 @@ pub static WALRECEIVER_RUNTIME: Lazy<Runtime> = Lazy::new(|| {
 pub static BACKGROUND_RUNTIME: Lazy<Runtime> = Lazy::new(|| {
     tokio::runtime::Builder::new_multi_thread()
         .thread_name("background op worker")
+        .worker_threads(THREADS_PER_RUNTIME.get())
         .enable_all()
         .build()
         .expect("Failed to create background op runtime")