use separate enum variant to represent index part for deleted timeline

pageserver/src/tenant.rs

@@ -58,6 +58,7 @@ use crate::task_mgr::TaskKind;
 use crate::tenant::config::TenantConfOpt;
 use crate::tenant::metadata::load_metadata;
 use crate::tenant::remote_timeline_client::index::IndexPart;
+use crate::tenant::remote_timeline_client::MaybeDeletedIndexPart;
 use crate::tenant::storage_layer::DeltaLayer;
 use crate::tenant::storage_layer::ImageLayer;
 use crate::tenant::storage_layer::Layer;
@@ -694,16 +695,9 @@ impl Tenant {
                         .await
                         .context("download index file")?;
 
-                    let remote_metadata = index_part.parse_metadata().context("parse metadata")?;
-
                     debug!("finished index part download");
 
-                    Result::<_, anyhow::Error>::Ok((
-                        timeline_id,
-                        client,
-                        index_part,
-                        remote_metadata,
-                    ))
+                    Result::<_, anyhow::Error>::Ok((timeline_id, client, index_part))
                 }
                 .map(move |res| {
                     res.with_context(|| format!("download index part for timeline {timeline_id}"))
@@ -717,10 +711,21 @@ impl Tenant {
         while let Some(result) = part_downloads.join_next().await {
             // NB: we already added timeline_id as context to the error
             let result: Result<_, anyhow::Error> = result.context("joinset task join")?;
-            let (timeline_id, client, index_part, remote_metadata) = result?;
+            let (timeline_id, client, index_part) = result?;
             debug!("successfully downloaded index part for timeline {timeline_id}");
-            timeline_ancestors.insert(timeline_id, remote_metadata);
-            remote_index_and_client.insert(timeline_id, (index_part, client));
+            match index_part {
+                MaybeDeletedIndexPart::IndexPart(index_part) => {
+                    timeline_ancestors.insert(
+                        timeline_id,
+                        index_part.parse_metadata().context("parse_metadata")?,
+                    );
+                    remote_index_and_client.insert(timeline_id, (index_part, client));
+                }
+                MaybeDeletedIndexPart::Deleted => {
+                    info!("timeline {} is deleted, skipping", timeline_id);
+                    continue;
+                }
+            }
         }
 
         // For every timeline, download the metadata file, scan the local directory,
@@ -732,11 +737,6 @@ impl Tenant {
                 .remove(&timeline_id)
                 .expect("just put it in above");
 
-            if index_part.is_deleted {
-                info!("timeline {} is deleted, skipping", timeline_id);
-                continue;
-            }
-
             // TODO again handle early failure
             self.load_remote_timeline(
                 timeline_id,
@@ -1048,7 +1048,6 @@ impl Tenant {
     /// Subroutine of `load_tenant`, to load an individual timeline
     ///
     /// NB: The parent is assumed to be already loaded!
-    #[instrument(skip(self, local_metadata, ctx), fields(timeline_id=%timeline_id))]
     async fn load_local_timeline(
         &self,
         timeline_id: TimelineId,
@@ -1067,10 +1066,13 @@ impl Tenant {
         let remote_startup_data = match &remote_client {
             Some(remote_client) => match remote_client.download_index_file().await {
                 Ok(index_part) => {
-                    if index_part.is_deleted {
-                        info!("is_deleted is set on remote, skipping");
-                        return Ok(());
-                    }
+                    let index_part = match index_part {
+                        MaybeDeletedIndexPart::IndexPart(index_part) => index_part,
+                        MaybeDeletedIndexPart::Deleted => {
+                            info!("is_deleted is set on remote, skipping");
+                            return Ok(());
+                        }
+                    };
 
                     let remote_metadata = index_part.parse_metadata().context("parse_metadata")?;
                     Some(RemoteStartupData {

pageserver/src/tenant/remote_timeline_client.rs

@@ -253,6 +253,11 @@ const FAILED_DOWNLOAD_RETRIES: u32 = 10;
 // retries. Uploads and deletions are retried forever, though.
 const FAILED_UPLOAD_WARN_THRESHOLD: u32 = 3;
 
+pub enum MaybeDeletedIndexPart {
+    IndexPart(IndexPart),
+    Deleted,
+}
+
 /// A client for accessing a timeline's data in remote storage.
 ///
 /// This takes care of managing the number of connections, and balancing them
@@ -367,12 +372,12 @@ impl RemoteTimelineClient {
     //
 
     /// Download index file
-    pub async fn download_index_file(&self) -> Result<IndexPart, DownloadError> {
+    pub async fn download_index_file(&self) -> Result<MaybeDeletedIndexPart, DownloadError> {
         let _unfinished_gauge_guard = self
             .metrics
             .call_begin(&RemoteOpFileKind::Index, &RemoteOpKind::Download);
 
-        download::download_index_part(
+        let index_part = download::download_index_part(
             self.conf,
             &self.storage_impl,
             self.tenant_id,
@@ -385,7 +390,13 @@ impl RemoteTimelineClient {
             RemoteOpKind::Download,
             Arc::clone(&self.metrics),
         )
-        .await
+        .await?;
+
+        if index_part.is_deleted {
+            Ok(MaybeDeletedIndexPart::Deleted)
+        } else {
+            Ok(MaybeDeletedIndexPart::IndexPart(index_part))
+        }
     }
 
     /// Download a (layer) file from `path`, into local filesystem.
@@ -1209,7 +1220,11 @@ mod tests {
         }
 
         // Download back the index.json, and check that the list of files is correct
-        let index_part = runtime.block_on(client.download_index_file())?;
+        let index_part = match runtime.block_on(client.download_index_file())? {
+            MaybeDeletedIndexPart::IndexPart(index_part) => index_part,
+            MaybeDeletedIndexPart::Deleted => panic!("unexpectedly got deleted index part"),
+        };
+
         assert_file_list(
             &index_part.timeline_layers,
             &[