test suite: add method for generation-aware detachment of a tenant (#5939)

Part of getpage@lsn benchmark epic:
https://github.com/neondatabase/neon/issues/5771

test_runner/fixtures/neon_fixtures.py

@@ -1572,7 +1572,7 @@ class NeonAttachmentService:
             self.running = False
         return self
 
-    def attach_hook(self, tenant_id: TenantId, pageserver_id: int) -> int:
+    def attach_hook_issue(self, tenant_id: TenantId, pageserver_id: int) -> int:
         response = requests.post(
             f"{self.env.control_plane_api}/attach-hook",
             json={"tenant_id": str(tenant_id), "node_id": pageserver_id},
@@ -1582,6 +1582,13 @@ class NeonAttachmentService:
         assert isinstance(gen, int)
         return gen
 
+    def attach_hook_drop(self, tenant_id: TenantId):
+        response = requests.post(
+            f"{self.env.control_plane_api}/attach-hook",
+            json={"tenant_id": str(tenant_id), "node_id": None},
+        )
+        response.raise_for_status()
+
     def __enter__(self) -> "NeonAttachmentService":
         return self
 
@@ -1781,13 +1788,20 @@ class NeonPageserver(PgProtocol):
         to call into the pageserver HTTP client.
         """
         if self.env.attachment_service is not None:
-            generation = self.env.attachment_service.attach_hook(tenant_id, self.id)
+            generation = self.env.attachment_service.attach_hook_issue(tenant_id, self.id)
         else:
             generation = None
 
         client = self.http_client()
         return client.tenant_attach(tenant_id, config, config_null, generation=generation)
 
+    def tenant_detach(self, tenant_id: TenantId):
+        if self.env.attachment_service is not None:
+            self.env.attachment_service.attach_hook_drop(tenant_id)
+
+        client = self.http_client()
+        return client.tenant_detach(tenant_id)
+
 
 def append_pageserver_param_overrides(
     params_to_update: List[str],

test_runner/regress/test_pageserver_generations.py

@@ -282,7 +282,7 @@ def test_deferred_deletion(neon_env_builder: NeonEnvBuilder):
 
     # Now advance the generation in the control plane: subsequent validations
     # from the running pageserver will fail.  No more deletions should happen.
-    env.attachment_service.attach_hook(env.initial_tenant, some_other_pageserver)
+    env.attachment_service.attach_hook_issue(env.initial_tenant, some_other_pageserver)
     generate_uploads_and_deletions(env, init=False)
 
     assert_deletion_queue(ps_http, lambda n: n > 0)
@@ -397,7 +397,7 @@ def test_deletion_queue_recovery(
     if keep_attachment == KeepAttachment.LOSE:
         some_other_pageserver = 101010
         assert env.attachment_service is not None
-        env.attachment_service.attach_hook(env.initial_tenant, some_other_pageserver)
+        env.attachment_service.attach_hook_issue(env.initial_tenant, some_other_pageserver)
 
     env.pageserver.start()