tenant shutdown: add some debug logging

This proved useful while debugging

https://github.com/neondatabase/neon/pull/4451#issuecomment-1584503248

resulting in

d4a86a415b

pageserver/src/tenant.rs

@@ -1926,6 +1926,8 @@ impl Tenant {
     /// This will attempt to shutdown even if tenant is broken.
     pub(crate) async fn shutdown(&self, freeze_and_flush: bool) -> Result<(), ShutdownError> {
         debug_assert_current_span_has_tenant_id();
+        debug!("start");
+
         // Set tenant (and its timlines) to Stoppping state.
         //
         // Since we can only transition into Stopping state after activation is complete,
@@ -1972,6 +1974,7 @@ impl Tenant {
         // this will additionally shutdown and await all timeline tasks.
         task_mgr::shutdown_tasks(None, Some(self.tenant_id), None).await;
 
+        debug!("complete");
         Ok(())
     }
 

pageserver/src/tenant/timeline.rs

@@ -684,8 +684,11 @@ impl Timeline {
     /// Flush to disk all data that was written with the put_* functions
     #[instrument(skip(self), fields(tenant_id=%self.tenant_id, timeline_id=%self.timeline_id))]
     pub async fn freeze_and_flush(&self) -> anyhow::Result<()> {
+        debug!("start");
         self.freeze_inmem_layer(false);
-        self.flush_frozen_layers_and_wait().await
+        let ret = self.flush_frozen_layers_and_wait().await;
+        debug!(is_err = ret.is_err(), "complete");
+        ret
     }
 
     /// Outermost timeline compaction operation; downloads needed layers.