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# Problem As pointed out through doc-comments in this PR, `drop_old_connection` is not cancellation-safe. This means we can leave a `handle_walreceiver_connection` tokio task dangling during Timeline shutdown. More details described in the corresponding issue #7062. # Solution Don't cancel-by-drop the `connection_manager_loop_step` from the `tokio::select!()` in the task_mgr task. Instead, transform the code to use a `CancellationToken` --- specifically, `task_mgr::shutdown_token()` --- and make code responsive to it. The `drop_old_connection()` is still not cancellation-safe and also doesn't get a cancellation token, because there's no point inside the function where we could return early if cancellation were requested using a token. We rely on the `handle_walreceiver_connection` to be sensitive to the `TaskHandle`s cancellation token (argument name: `cancellation`). Currently it checks for `cancellation` on each WAL message. It is probably also sensitive to `Timeline::cancel` because ultimately all that `handle_walreceiver_connection` does is interact with the `Timeline`. In summary, the above means that the following code (which is found in `Timeline::shutdown`) now might **take longer**, but actually ensures that all `handle_walreceiver_connection` tasks are finished: ```rust task_mgr::shutdown_tasks( Some(TaskKind::WalReceiverManager), Some(self.tenant_shard_id), Some(self.timeline_id) ) ``` # Refs refs #7062