bandaid to avoid concurrent timeline downloading until proper refactoring/fix

pageserver/src/layered_repository/image_layer.rs

@@ -173,7 +173,14 @@ impl Layer for ImageLayer {
                     .as_ref()
                     .unwrap()
                     .chapter_reader(BLOCKY_IMAGES_CHAPTER)?;
-                chapter.read_exact_at(&mut buf, offset)?;
+
+                chapter.read_exact_at(&mut buf, offset).with_context(|| {
+                    format!(
+                        "failed to read page from data file {} at offset {}",
+                        self.filename().display(),
+                        offset
+                    )
+                })?;
 
                 buf
             }

test_runner/batch_others/test_remote_storage.py

@@ -74,8 +74,13 @@ def test_remote_storage_backup_and_restore(zenith_env_builder: ZenithEnvBuilder,
     ##### Second start, restore the data and ensure it's the same
     env.pageserver.start()
 
-    log.info("waiting for timeline redownload")
     client = env.pageserver.http_client()
+    client.timeline_attach(UUID(tenant_id), UUID(timeline_id))
+    # FIXME cannot handle duplicate download requests (which might be caused by repeated timeline detail calls)
+    #   subject to fix in https://github.com/zenithdb/zenith/issues/997
+    time.sleep(5)
+
+    log.info("waiting for timeline redownload")
     attempts = 0
     while True:
         timeline_details = client.timeline_detail(UUID(tenant_id), UUID(timeline_id))

test_runner/batch_others/test_tenant_relocation.py

@@ -192,7 +192,7 @@ def test_tenant_relocation(zenith_env_builder: ZenithEnvBuilder,
                                new_pageserver_pg_port,
                                new_pageserver_http_port):
 
-        # call to attach timeline to new timeline
+        # call to attach timeline to new pageserver
         new_pageserver_http_client.timeline_attach(UUID(tenant), UUID(timeline))
         # FIXME cannot handle duplicate download requests, subject to fix in https://github.com/zenithdb/zenith/issues/997
         time.sleep(5)