Skip to content

background-tasks.md

Latest commit

 

History

History
59 lines (43 loc) · 3.31 KB

background-tasks.md

File metadata and controls

59 lines (43 loc) · 3.31 KB
Raw

Background tasks

Purpose

Testing, connecting and finding documents can take long, up to the driver's server selection timeout. They run as background tasks in Rust, so the UI stays responsive and the user can cancel them.

How it works

Rust (task_manager/)

  • TaskManager keeps two maps keyed by a uuid: the tokio JoinHandle of each task and its AbortHandle.
  • A start_* command passes its future to spawn_task, which spawns it and returns the id at once. The future resolves to Result<serde_json::Value, serde_json::Value>: the result, or the serialized error.
  • await_task_result(id) takes the JoinHandle out of the map and awaits it:
    • Ok(value) is the result.
    • The future's error becomes TaskError::Failed(value).
    • An aborted task becomes TaskError::Cancelled, a panic becomes Failed with kind Panic.
    • Afterwards the abort handle is removed.
  • cancel_task(id) calls abort() on the handle. An unknown id is TaskError::NotFound.
  • TaskError serializes like every other error, with kind, message and user_message. For Failed the message is the JSON text of the original error.

The commands that use it are start_test_connection, start_connect and start_find_documents.

UI (composables/useAbortableCommand.ts)

  • abortableInvoke(startCommand, args, { signal }) invokes the start command, then await_task_result. If the AbortSignal fires in between, it calls cancel_task.
  • Errors are unwrapped:
    • an aborted signal or kind Cancelled throws TaskCancelledError
    • kind Failed throws the original error, parsed back from message, so the caller gets the driver's user_message
    • anything else is rethrown as it is
  • ConnectionServiceIPC.testConnection, connect and findDocuments use it. The store keeps one AbortController for the test and one for connecting; Cancel calls abort() on it.

Decisions

  • A task registry of our own instead of a timeout (a14c8fc, issue #27). The user decides when to give up, and the same mechanism serves every slow command.
  • The error travels as JSON and is unwrapped in the UI, so the toast shows the driver's message and not "The operation failed".

Building steps

Date Step Commit
2026-02-21 TaskManager, cancel_task, await_task_result, abortableInvoke; test and connect as tasks a14c8fc
2026-02-23 start_find_documents as a task cbc9b83

Limits and open points

  • The query tab doesn't use it. TabViewQuery invokes start_find_documents and await_task_result directly instead of ConnectionServiceIPC.findDocuments. A query can't be cancelled, and its errors aren't unwrapped (see query-tab.md).
  • A task that is never awaited stays in both maps. Today every start is awaited right after.
  • Aborting drops the future. A MongoDB operation that already reached the server is not killed on the server.
  • No tests for the task manager.

Where the code is

What Path
Registry src-tauri/src/task_manager/task_manager.rs
Commands src-tauri/src/task_manager/commands.rs
Error src-tauri/src/task_manager/task_error.rs
UI helper src/composables/useAbortableCommand.ts
Callers src/domains/connections/services/ConnectionServiceIPC.ts, src/stores/connectionStore.ts