From 9ce6e7c86bde0bea1d8f862bc4b443a2f3eca105 Mon Sep 17 00:00:00 2001
From: Christian Schwarz <me@cschwarz.com>
Date: Fri, 16 Jun 2023 17:31:18 +0200
Subject: [PATCH] convert more 'no-op if Creating' into check_at_caller+asserts

---
 pageserver/src/tenant.rs          | 13 +++++++++----
 pageserver/src/tenant/timeline.rs | 17 +++++++----------
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/pageserver/src/tenant.rs b/pageserver/src/tenant.rs
index f318090712..71dc061485 100644
--- a/pageserver/src/tenant.rs
+++ b/pageserver/src/tenant.rs
@@ -1757,6 +1757,11 @@ impl Tenant {
         // execute on each timeline on the JoinSet, join after.
         let per_timeline = |timeline: Arc<Timeline>| {
             async move {
+                if let TimelineState::Creating = timeline.current_state() {
+                    debug!("timeline is Creating, no need to flush it");
+                    // TODO cancel creation? Or is that done by higher level shutdown code?
+                    return;
+                }
                 match timeline.freeze_and_flush().await {
                     Ok(()) => {}
                     Err(err) => {
@@ -2284,10 +2289,10 @@ impl Tenant {
         }
 
         let timelines_accessor = self.timelines.lock().unwrap();
-        let not_broken_timelines = timelines_accessor
-            .values()
-            .filter(|timeline| !timeline.is_broken());
-        for timeline in not_broken_timelines {
+        let timelines_to_stop = timelines_accessor.values().filter(|timeline| {
+            !timeline.is_broken() && !matches!(timeline.current_state(), TimelineState::Creating)
+        });
+        for timeline in timelines_to_stop {
             timeline.set_state(TimelineState::Stopping);
         }
         Ok(())
diff --git a/pageserver/src/tenant/timeline.rs b/pageserver/src/tenant/timeline.rs
index ca8942b577..1b7141cd58 100644
--- a/pageserver/src/tenant/timeline.rs
+++ b/pageserver/src/tenant/timeline.rs
@@ -691,12 +691,9 @@ impl Timeline {
     #[instrument(skip(self), fields(tenant_id=%self.tenant_id, timeline_id=%self.timeline_id))]
     pub async fn freeze_and_flush(&self) -> anyhow::Result<()> {
         if self.current_state() == TimelineState::Creating {
-            debug!("timelines in Creating state are never written to");
-            assert!(
-                self.layers.read().await.open_layer.is_none(),
-                "would have nothing to flush anyways"
-            );
-            return Ok(());
+            // make a few additional sanity checks before panicking
+            assert!(self.layers.read().await.open_layer.is_none());
+            panic!("caller must prevent calls for timelines in Creating state")
         }
         self.freeze_inmem_layer(false).await;
         self.flush_frozen_layers_and_wait().await
@@ -704,10 +701,10 @@ impl Timeline {
 
     /// Outermost timeline compaction operation; downloads needed layers.
     pub async fn compact(self: &Arc<Self>, ctx: &RequestContext) -> anyhow::Result<()> {
-        if self.current_state() == TimelineState::Creating {
-            debug!("timelines is in Creating state");
-            return Ok(());
-        }
+        assert!(
+            !matches!(self.current_state(), TimelineState::Creating),
+            "caller must prevent calls for timelines in Creating state"
+        );
 
         const ROUNDS: usize = 2;