Demote deletion warning, list files (#4688)

Handle test failures like:

```
AssertionError: assert not ['$ts  WARN delete_timeline{tenant_id=X timeline_id=Y}: About to remove 1 files\n']
```

Instead of logging:

```
WARN delete_timeline{tenant_id=X timeline_id=Y}: Found 1 files not bound to index_file.json, proceeding with their deletion
WARN delete_timeline{tenant_id=X timeline_id=Y}: About to remove 1 files
```

For each one operation of timeline deletion, list all unref files with
`info!`, and then continue to delete them with the added spice of
logging the rare/never happening non-utf8 name with `warn!`.

Rationale for `info!` instead of `warn!`: this is a normal operation;
like we had mentioned in `test_import.py` -- basically whenever we
delete a timeline which is not idle.

Rationale for N * (`ìnfo!`|`warn!`): symmetry for the layer deletions;
if we could ever need those, we could also need these for layer files
which are not yet mentioned in `index_part.json`.

---------

Co-authored-by: Christian Schwarz <christian@neon.tech>

libs/remote_storage/src/lib.rs

@@ -50,6 +50,12 @@ const REMOTE_STORAGE_PREFIX_SEPARATOR: char = '/';
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct RemotePath(PathBuf);
 
+impl std::fmt::Display for RemotePath {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.0.display())
+    }
+}
+
 impl RemotePath {
     pub fn new(relative_path: &Path) -> anyhow::Result<Self> {
         anyhow::ensure!(

pageserver/src/tenant/remote_timeline_client.rs

@@ -840,14 +840,16 @@ impl RemoteTimelineClient {
         let remaining: Vec<RemotePath> = remaining
             .into_iter()
             .filter(|p| p.object_name() != Some(IndexPart::FILE_NAME))
+            .inspect(|path| {
+                if let Some(name) = path.object_name() {
+                    info!(%name, "deleting a file not referenced from index_part.json");
+                } else {
+                    warn!(%path, "deleting a nameless or non-utf8 object not referenced from index_part.json");
+                }
+            })
             .collect();
 
         if !remaining.is_empty() {
-            warn!(
-                "Found {} files not bound to index_file.json, proceeding with their deletion",
-                remaining.len()
-            );
-            warn!("About to remove {} files", remaining.len());
             self.storage_impl.delete_objects(&remaining).await?;
         }
 
@@ -856,7 +858,7 @@ impl RemoteTimelineClient {
         debug!("deleting index part");
         self.storage_impl.delete(&index_file_path).await?;
 
-        info!(deletions_queued, "done deleting, including index_part.json");
+        info!(prefix=%timeline_storage_path, referenced=deletions_queued, not_referenced=%remaining.len(), "done deleting in timeline prefix, including index_part.json");
 
         Ok(())
     }

test_runner/regress/test_import.py

@@ -149,12 +149,6 @@ def test_import_from_vanilla(test_output_dir, pg_bin, vanilla_pg, neon_env_build
         ".*WARN.*ignored .* unexpected bytes after the tar archive.*"
     )
 
-    # NOTE: delete can easily come before upload operations are completed
-    # https://github.com/neondatabase/neon/issues/4326
-    env.pageserver.allowed_errors.append(
-        ".*files not bound to index_file.json, proceeding with their deletion.*"
-    )
-
     timeline_delete_wait_completed(client, tenant, timeline)
 
     # Importing correct backup works

test_runner/regress/test_remote_storage.py

@@ -598,9 +598,6 @@ def test_timeline_deletion_with_files_stuck_in_upload_queue(
         ".* ERROR .*Error processing HTTP request: InternalServerError\\(timeline is Stopping"
     )
 
-    env.pageserver.allowed_errors.append(
-        ".*files not bound to index_file.json, proceeding with their deletion.*"
-    )
     timeline_delete_wait_completed(client, tenant_id, timeline_id)
 
     assert not timeline_path.exists()