From 78e94415645ea2299497a6e492ca828db8aa5f5d Mon Sep 17 00:00:00 2001
From: Sayan Nandan <nandansayan@outlook.com>
Date: Fri, 14 May 2021 21:07:37 +0530
Subject: [PATCH] Spawn blocking I/O tasks on a dedicated thread

---
 server/src/coredb/mod.rs      |  4 ++++
 server/src/diskstore/flock.rs |  6 ++++++
 server/src/diskstore/mod.rs   | 17 ++++++++++++++++-
 3 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/server/src/coredb/mod.rs b/server/src/coredb/mod.rs
index 16be5d14..63e93e2b 100644
--- a/server/src/coredb/mod.rs
+++ b/server/src/coredb/mod.rs
@@ -243,6 +243,10 @@ impl CoreDB {
             println!("{:#?}", self.acquire_read());
         }
     }
+    
+    pub fn poison(&self) {
+        (*self.shared).table.write().poisoned = true;
+    }
 
     /// Check if snapshotting is enabled
     pub fn is_snapshot_enabled(&self) -> bool {
diff --git a/server/src/diskstore/flock.rs b/server/src/diskstore/flock.rs
index f9bd8306..77d400bd 100644
--- a/server/src/diskstore/flock.rs
+++ b/server/src/diskstore/flock.rs
@@ -98,6 +98,12 @@ impl FileLock {
         // Now write to the file
         self.file.write_all(bytes)
     }
+    pub fn try_clone(&self) -> Result<Self> {
+        Ok(FileLock {
+            file: self.file.try_clone()?,
+            unlocked: self.unlocked,
+        })
+    }
 }
 
 impl Drop for FileLock {
diff --git a/server/src/diskstore/mod.rs b/server/src/diskstore/mod.rs
index 17ab33e9..f4d26d2d 100644
--- a/server/src/diskstore/mod.rs
+++ b/server/src/diskstore/mod.rs
@@ -201,7 +201,22 @@ pub async fn bgsave_scheduler(
                 tokio::select! {
                     // Sleep until `duration` from the current time instant
                     _ = time::sleep_until(time::Instant::now() + duration) => {
-                        if !handle.shared.run_bgsave(&mut file) {break;}
+                        let clone_file = match file.try_clone() {
+                            Ok(cloned_descriptor) => cloned_descriptor,
+                            Err(e) => {
+                                // failed to get a clone of the descriptor ugh
+                                handle.poison();
+                                log::error!("BGSAVE service failed to clone descriptor: '{}'", e);
+                                continue;
+                            }
+                        };
+                        let cloned_handle = handle.clone();
+                        let continue_running = tokio::task::spawn_blocking(move || {
+                            let mut owned_file = clone_file;
+                            let owned_handle = cloned_handle;
+                            owned_handle.shared.run_bgsave(&mut owned_file)
+                        }).await.expect("Something caused the background service to panic");
+                        if !continue_running {break;}
                     }
                     // Otherwise wait for a notification
                     _ = handle.shared.bgsave_task.notified() => {