pageserver: remove AncestorStopping error variants (#7916)

## Problem

In all cases, AncestorStopping is equivalent to Cancelled.

This became more obvious in
https://github.com/neondatabase/neon/pull/7912#discussion_r1620582309
when updating these error types.

## Summary of changes

- Remove AncestorStopping, always use Cancelled instead

pageserver/src/consumption_metrics.rs

@@ -358,7 +358,7 @@ async fn calculate_and_log(tenant: &Tenant, cancel: &CancellationToken, ctx: &Re
     // mean the synthetic size worker should terminate.
     let shutting_down = matches!(
         e.downcast_ref::<PageReconstructError>(),
-        Some(PageReconstructError::Cancelled | PageReconstructError::AncestorStopping(_))
+        Some(PageReconstructError::Cancelled)
     );
 
     if !shutting_down {

pageserver/src/http/routes.rs

@@ -184,9 +184,6 @@ impl From<PageReconstructError> for ApiError {
             PageReconstructError::Cancelled => {
                 ApiError::InternalServerError(anyhow::anyhow!("request was cancelled"))
             }
-            PageReconstructError::AncestorStopping(_) => {
-                ApiError::ResourceUnavailable(format!("{pre}").into())
-            }
             PageReconstructError::AncestorLsnTimeout(e) => ApiError::Timeout(format!("{e}").into()),
             PageReconstructError::WalRedo(pre) => ApiError::InternalServerError(pre),
         }

pageserver/src/pgdatadir_mapping.rs

@@ -115,9 +115,7 @@ impl From<PageReconstructError> for CollectKeySpaceError {
 impl From<PageReconstructError> for CalculateLogicalSizeError {
     fn from(pre: PageReconstructError) -> Self {
         match pre {
-            PageReconstructError::AncestorStopping(_) | PageReconstructError::Cancelled => {
-                Self::Cancelled
-            }
+            PageReconstructError::Cancelled => Self::Cancelled,
             _ => Self::PageRead(pre),
         }
     }
@@ -1614,8 +1612,7 @@ impl<'a> DatadirModification<'a> {
                         aux_files.dir = Some(dir);
                     }
                     Err(
-                        e @ (PageReconstructError::AncestorStopping(_)
-                        | PageReconstructError::Cancelled
+                        e @ (PageReconstructError::Cancelled
                         | PageReconstructError::AncestorLsnTimeout(_)),
                     ) => {
                         // Important that we do not interpret a shutdown error as "not found" and thereby

pageserver/src/tenant/timeline.rs

@@ -501,10 +501,6 @@ pub(crate) enum PageReconstructError {
     #[error("timeline shutting down")]
     Cancelled,
 
-    /// The ancestor of this is being stopped
-    #[error("ancestor timeline {0} is being stopped")]
-    AncestorStopping(TimelineId),
-
     /// An error happened replaying WAL records
     #[error(transparent)]
     WalRedo(anyhow::Error),
@@ -569,7 +565,7 @@ impl PageReconstructError {
         match self {
             Other(_) => false,
             AncestorLsnTimeout(_) => false,
-            Cancelled | AncestorStopping(_) => true,
+            Cancelled => true,
             WalRedo(_) => false,
             MissingKey { .. } => false,
         }
@@ -645,9 +641,6 @@ pub(crate) enum GetVectoredError {
 
 #[derive(thiserror::Error, Debug)]
 pub(crate) enum GetReadyAncestorError {
-    #[error("ancestor timeline {0} is being stopped")]
-    AncestorStopping(TimelineId),
-
     #[error("Ancestor LSN wait error: {0}")]
     AncestorLsnTimeout(#[from] WaitLsnError),
 
@@ -757,7 +750,6 @@ impl From<GetReadyAncestorError> for PageReconstructError {
     fn from(e: GetReadyAncestorError) -> Self {
         use GetReadyAncestorError::*;
         match e {
-            AncestorStopping(tid) => PageReconstructError::AncestorStopping(tid),
             AncestorLsnTimeout(wait_err) => PageReconstructError::AncestorLsnTimeout(wait_err),
             bad_state @ BadState { .. } => PageReconstructError::Other(anyhow::anyhow!(bad_state)),
             Cancelled => PageReconstructError::Cancelled,
@@ -1192,9 +1184,7 @@ impl Timeline {
 
                 use PageReconstructError::*;
                 match block {
-                    Err(Cancelled | AncestorStopping(_)) => {
-                        return Err(GetVectoredError::Cancelled)
-                    }
+                    Err(Cancelled) => return Err(GetVectoredError::Cancelled),
                     Err(MissingKey(_))
                         if NON_INHERITED_RANGE.contains(&key)
                             || NON_INHERITED_SPARSE_RANGE.contains(&key) =>
@@ -3585,9 +3575,8 @@ impl Timeline {
         match ancestor.wait_to_become_active(ctx).await {
             Ok(()) => {}
             Err(TimelineState::Stopping) => {
-                return Err(GetReadyAncestorError::AncestorStopping(
-                    ancestor.timeline_id,
-                ));
+                // If an ancestor is stopping, it means the tenant is stopping: handle this the same as if this timeline was stopping.
+                return Err(GetReadyAncestorError::Cancelled);
             }
             Err(state) => {
                 return Err(GetReadyAncestorError::BadState {

test_runner/fixtures/pageserver/allowed_errors.py

@@ -66,7 +66,7 @@ DEFAULT_PAGESERVER_ALLOWED_ERRORS = (
     ".*query handler for 'pagestream.*failed: Timeline .* is not active",  # timeline delete in progress
     ".*task iteration took longer than the configured period.*",
     # these can happen anytime we do compactions from background task and shutdown pageserver
-    r".*ERROR.*ancestor timeline \S+ is being stopped",
+    ".*could not compact.*cancelled.*",
     # this is expected given our collaborative shutdown approach for the UploadQueue
     ".*Compaction failed.*, retrying in .*: Other\\(queue is in state Stopped.*",
     ".*Compaction failed.*, retrying in .*: ShuttingDown",