From 4db4f42decff883ecf277354d990b3b086d80d97 Mon Sep 17 00:00:00 2001
From: Alex Chi Z <chi@neon.tech>
Date: Wed, 28 Jun 2023 14:40:41 -0400
Subject: [PATCH] correctly handle compaction

Signed-off-by: Alex Chi Z <chi@neon.tech>
---
 pageserver/src/tenant/tasks.rs    |  8 +++++---
 pageserver/src/tenant/timeline.rs | 14 ++++++++------
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/pageserver/src/tenant/tasks.rs b/pageserver/src/tenant/tasks.rs
index e33d1aec55..f6a3b96943 100644
--- a/pageserver/src/tenant/tasks.rs
+++ b/pageserver/src/tenant/tasks.rs
@@ -23,8 +23,8 @@ pub fn start_background_loops(
 ) {
     let tenant_id = tenant.tenant_id;
     // start two compaction threads
-    let range = if ENABLE_TIERED_COMPACTION { 0..2 } else { 0..1 };
-    for _ in range {
+    let range = if ENABLE_TIERED_COMPACTION { 0..4 } else { 0..1 };
+    for cpt_id in range {
         task_mgr::spawn(
             BACKGROUND_RUNTIME.handle(),
             TaskKind::Compaction,
@@ -42,7 +42,9 @@ pub fn start_background_loops(
                         _ = completion::Barrier::maybe_wait(background_jobs_can_start) => {}
                     };
                     compaction_loop(tenant, cancel)
-                        .instrument(info_span!("compaction_loop", tenant_id = %tenant_id))
+                        .instrument(
+                            info_span!("compaction_loop", tenant_id = %tenant_id, cpt_id = %cpt_id),
+                        )
                         .await;
                     Ok(())
                 }
diff --git a/pageserver/src/tenant/timeline.rs b/pageserver/src/tenant/timeline.rs
index 3916397a80..56bbde5033 100644
--- a/pageserver/src/tenant/timeline.rs
+++ b/pageserver/src/tenant/timeline.rs
@@ -79,7 +79,7 @@ use self::eviction_task::EvictionTaskTimelineState;
 use self::walreceiver::{WalReceiver, WalReceiverConf};
 
 use super::config::TenantConf;
-use super::layer_cache::{DeleteGuardRead, LayerCache, DeleteGuardWrite};
+use super::layer_cache::{DeleteGuardRead, DeleteGuardWrite, LayerCache};
 use super::layer_map::BatchedUpdates;
 use super::remote_timeline_client::index::IndexPart;
 use super::remote_timeline_client::RemoteTimelineClient;
@@ -4200,11 +4200,6 @@ impl Timeline {
 
         drop(all_keys_iter); // So that deltas_to_compact is no longer borrowed
 
-        let mut compacting_tiers = self.compacting.lock().unwrap();
-        for &tier in &tier_to_compact {
-            compacting_tiers.remove(&tier);
-        }
-
         Ok(Some(CompactTieredPhase1Result {
             new_layers,
             new_tier_at: *tier_to_compact.last().unwrap(),
@@ -4318,6 +4313,13 @@ impl Timeline {
         println!("after compaction:");
         layers.dump(false, ctx)?;
 
+        let mut compacting_tiers = self.compacting.lock().unwrap();
+        for &tier in &removed_tiers {
+            compacting_tiers.remove(&tier);
+        }
+
+        info!("compaction complete, removed_tiers = {removed_tiers:?}, new_tier_at = {new_tier_at}");
+
         drop_wlock(guard);
 
         // Also schedule the deletions in remote storage