test: funroll-loop first iteration in test_retried_detach_ancestor_after_failed_reparenting

test_runner/regress/test_timeline_detach_ancestor.py

@@ -1163,7 +1163,7 @@ def test_retried_detach_ancestor_after_failed_reparenting(neon_env_builder: Neon
     # tracked offset in the pageserver log which is at least at the most recent activation
     offset = None
 
-    def another_detach():
+    def try_detach():
         with pytest.raises(
             PageserverApiException,
             match=".*failed to reparent all candidate timelines, please retry",
@@ -1171,48 +1171,56 @@ def test_retried_detach_ancestor_after_failed_reparenting(neon_env_builder: Neon
             http.detach_ancestor(env.initial_tenant, detached)
         assert exc.value.status_code == 500
 
-    for nth_round in range(3):
+    # first round -- do more checking to make sure the gc gets paused
-        another_detach()
+    try_detach()
 
     assert (
         http.timeline_detail(env.initial_tenant, detached)["ancestor_timeline_id"] is None
     ), "first round should had detached 'detached'"
 
     reparented, not_reparented = reparenting_progress(timelines)
-        assert reparented == nth_round + 1
+    assert reparented == 1
 
-        if nth_round == 0:
     time.sleep(2)
     _, offset = env.pageserver.assert_log_contains(
         ".*INFO request\\{method=PUT path=/v1/tenant/[0-9a-f]{32}/timeline/[0-9a-f]{32}/detach_ancestor .*\\}: Handling request",
         offset,
     )
-            _, offset = env.pageserver.assert_log_contains(
+    _, offset = env.pageserver.assert_log_contains(".*: attach finished, activating", offset)
-                ".*: attach finished, activating", offset
-            )
     _, offset = env.pageserver.assert_log_contains(
         ".* gc_loop.*: Skipping GC while there is an ongoing detach_ancestor attempt",
         offset,
     )
     metric = remote_storage_copy_requests()
     assert metric != 0
-            # make sure the gc blocking is persistent
+    # make sure the gc blocking is persistent over a restart
     env.pageserver.restart()
     env.pageserver.quiesce_tenants()
     time.sleep(2)
-            _, offset = env.pageserver.assert_log_contains(
+    _, offset = env.pageserver.assert_log_contains(".*: attach finished, activating", offset)
-                ".*: attach finished, activating", offset
+    assert env.pageserver.log_contains(".* gc_loop.*: [0-9] timelines need GC", offset) is None
-            )
     _, offset = env.pageserver.assert_log_contains(
         ".* gc_loop.*: Skipping GC while there is an ongoing detach_ancestor attempt",
         offset,
     )
     # restore failpoint for the next reparented
     http.configure_failpoints(("timeline-detach-ancestor::allow_one_reparented", "return"))
-        else:
+
-            _, offset = env.pageserver.assert_log_contains(
+    reparented_before = reparented
-                ".*: attach finished, activating", offset
+
-            )
+    # do two more rounds
+    for _ in range(2):
+        try_detach()
+
+        assert (
+            http.timeline_detail(env.initial_tenant, detached)["ancestor_timeline_id"] is None
+        ), "first round should had detached 'detached'"
+
+        reparented, not_reparented = reparenting_progress(timelines)
+        assert reparented == reparented_before + 1
+        reparented_before = reparented
+
+        _, offset = env.pageserver.assert_log_contains(".*: attach finished, activating", offset)
         metric = remote_storage_copy_requests()
         assert metric == 0, "copies happen in the first round"
 
@@ -1221,7 +1229,8 @@ def test_retried_detach_ancestor_after_failed_reparenting(neon_env_builder: Neon
 
     http.configure_failpoints(("timeline-detach-ancestor::complete_before_uploading", "return"))
 
-    # almost final round, the failpoint is hit no longer, and everything completes
+    # almost final round, the failpoint is hit no longer as there is only one reparented and one always gets to succeed.
+    # the tenant is restarted once more, but we fail during completing.
     with pytest.raises(
         PageserverApiException, match=".* timeline-detach-ancestor::complete_before_uploading"
     ) as exc: