From 46ca6f17c5a27009532f2c8c939893d7004f1588 Mon Sep 17 00:00:00 2001
From: Joonas Koivunen <joonas@neon.tech>
Date: Tue, 23 Jul 2024 14:20:02 +0000
Subject: [PATCH] plumbing: notify shared state of existing attempt

---
 pageserver/src/tenant.rs                          | 6 ++++++
 pageserver/src/tenant/mgr.rs                      | 6 ++++++
 pageserver/src/tenant/timeline/detach_ancestor.rs | 4 ++++
 3 files changed, 16 insertions(+)

diff --git a/pageserver/src/tenant.rs b/pageserver/src/tenant.rs
index 603d095e44..fdd6434e49 100644
--- a/pageserver/src/tenant.rs
+++ b/pageserver/src/tenant.rs
@@ -35,6 +35,7 @@ use std::collections::BTreeMap;
 use std::fmt;
 use std::time::SystemTime;
 use storage_broker::BrokerClientChannel;
+use timeline::detach_ancestor;
 use tokio::io::BufReader;
 use tokio::sync::watch;
 use tokio::task::JoinSet;
@@ -678,6 +679,7 @@ impl Tenant {
         shard_identity: ShardIdentity,
         init_order: Option<InitializationOrder>,
         mode: SpawnMode,
+        existing_detach_attempt: Option<&detach_ancestor::Attempt>,
         ctx: &RequestContext,
     ) -> Arc<Tenant> {
         let wal_redo_manager = Arc::new(WalRedoManager::from(PostgresRedoManager::new(
@@ -707,6 +709,10 @@ impl Tenant {
             l0_flush_global_state,
         ));
 
+        if let Some(attempt) = existing_detach_attempt {
+            tenant.ongoing_timeline_detach.notify(attempt);
+        }
+
         // The attach task will carry a GateGuard, so that shutdown() reliably waits for it to drop out if
         // we shut down while attaching.
         let attach_gate_guard = tenant
diff --git a/pageserver/src/tenant/mgr.rs b/pageserver/src/tenant/mgr.rs
index 7f9b3b7e93..445676c4ae 100644
--- a/pageserver/src/tenant/mgr.rs
+++ b/pageserver/src/tenant/mgr.rs
@@ -676,6 +676,7 @@ pub async fn init_tenant_mgr(
                 shard_identity,
                 Some(init_order.clone()),
                 SpawnMode::Lazy,
+                None,
                 &ctx,
             )),
             LocationMode::Secondary(secondary_conf) => {
@@ -724,6 +725,7 @@ fn tenant_spawn(
     shard_identity: ShardIdentity,
     init_order: Option<InitializationOrder>,
     mode: SpawnMode,
+    existing_detach_attempt: Option<&detach_ancestor::Attempt>,
     ctx: &RequestContext,
 ) -> Arc<Tenant> {
     // All these conditions should have been satisfied by our caller: the tenant dir exists, is a well formed
@@ -744,6 +746,7 @@ fn tenant_spawn(
         shard_identity,
         init_order,
         mode,
+        existing_detach_attempt,
         ctx,
     )
 }
@@ -1191,6 +1194,7 @@ impl TenantManager {
                     shard_identity,
                     None,
                     spawn_mode,
+                    None,
                     ctx,
                 );
 
@@ -1312,6 +1316,7 @@ impl TenantManager {
             shard_identity,
             None,
             SpawnMode::Eager,
+            None,
             ctx,
         );
 
@@ -2052,6 +2057,7 @@ impl TenantManager {
             shard_identity,
             None,
             SpawnMode::Eager,
+            Some(&attempt),
             ctx,
         );
 
diff --git a/pageserver/src/tenant/timeline/detach_ancestor.rs b/pageserver/src/tenant/timeline/detach_ancestor.rs
index e79a1a0549..849596ea8c 100644
--- a/pageserver/src/tenant/timeline/detach_ancestor.rs
+++ b/pageserver/src/tenant/timeline/detach_ancestor.rs
@@ -134,6 +134,10 @@ impl Default for SharedState {
 }
 
 impl SharedState {
+    /// Notify an uninitialized shared state that an attempt to detach timeline ancestor continues
+    /// from previous instance.
+    pub(crate) fn notify(&self, attempt: &Attempt) {}
+
     /// Only GC must be paused while a detach ancestor is ongoing. Compaction can happen, to aid
     /// with any ongoing ingestion. Compaction even after restart is ok because layers will not be
     /// removed until the detach has been persistently completed.