OUT-3964 | Tasks App - Task(s) Created Using Template Not Saving

[arpandhakal]

Problem

Creating a task from a template with many sub-templates left some subtasks unsaved, and opening the task detail threw:

P2024 — Timed out fetching a new connection from the connection pool (in getSubtaskCounts → getSubtaskStatus)

Root cause

Applying a template fanned out every sub-template's task creation concurrently via Promise.all. Each createSubtasksFromTemplate → createTask is heavy (multiple queries + activity log + notifications trigger + webhook). For a large template (e.g. 90 sub-templates), ~90 concurrent createTask calls saturated the Prisma connection pool — so:

• some subtask creations failed → not all subtasks saved
• the subsequent single-query getSubtaskCounts on the detail page couldn't acquire a connection within pool_timeout → P2024

getSubtaskCounts was the victim, not the cause.

Fix

Bound the fan-out concurrency so it can't monopolize the pool, independent of pool size:

• src/utils/array.ts — add chunk + runInBatches(items, size, handler) (at most size run at once, one batch after another)
• src/constants/tasks.ts — subtaskTemplateBatchSize = 5
• tasks.service.ts & public.service.ts — both template-apply sites use runInBatches instead of Promise.all

Ordering is preserved (the per-subtask timestamp is still derived from index).

Notes

• Pure concurrency change — no behavior/schema change.
• subtaskTemplateBatchSize is deliberately conservative; bump it in one place if more throughput is wanted.

🤖 Generated with Claude Code

[linear-code]

OUT-3964

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
tasks-app	Ready	Preview, Comment	Jul 10, 2026 8:53am

[greptile-apps]

Greptile Summary

This PR limits template subtask creation so large templates do not exhaust the database pool. The main changes are:

• Adds chunk and runInBatches helpers for bounded async fan-out.
• Adds a shared subtask-template batch-size constant.
• Uses batched subtask creation in both private and public task creation flows.
• Moves applied-template lookup into the shared subtask creation helper.
• Changes subtask-template failures to delete the parent task and return an error.

Confidence Score: 4/5

This is close, but the rollback race should be fixed before merging.

• Batched creation preserves the original subtask ordering index.
• Import and helper changes look consistent with the project setup.
• A failed child creation can delete the parent while sibling child creations in the same batch continue and emit events for rows that are later removed.

src/app/api/tasks/tasksShared.service.ts

Important Files Changed

Filename	Overview
src/app/api/tasks/tasksShared.service.ts	Refactors template subtask creation to fetch the applied template internally and roll back the parent task when a child creation fails.
src/app/api/tasks/tasks.service.ts	Switches private template subtask creation from unbounded fan-out to batched execution while preserving the original index-based timestamp order.
src/app/api/tasks/public/public.service.ts	Applies the same batched template subtask creation flow to public task creation.
src/utils/array.ts	Adds array chunking and bounded async batch execution helpers.
src/constants/tasks.ts	Adds the shared batch-size constant for template subtask creation.

Comments Outside Diff (1)

1. src/app/api/tasks/tasksShared.service.ts, line 630-635 (link)

   Rollback races siblings When one subtask fails, this handler deletes the parent while other subtasks in the same batch may still be running. runInBatches starts each batch with Promise.all, so a rejection does not cancel sibling createSubtasksFromTemplate calls. A sibling can finish createTask and dispatch task-created notifications or webhooks, then have its row removed by the parent delete cascade. The API fails loudly, but external callers can still receive events for subtasks that no longer exist. The rollback needs to be coordinated outside the concurrent child handler, or the child creations need to avoid non-transactional side effects while siblings can still fail.

_{Reviews (3): Last reviewed commit: "fix(templates): restore all-or-nothing r..." | Re-trigger Greptile}

[vercel]

Deployment failed with the following error:

Deploying Serverless Functions to multiple regions is restricted to the Pro and Enterprise plans.

Learn More: https://vercel.link/multiple-function-regions

[arpandhakal]

@greptile please review again

[arpandhakal]

please re review @greptile

[priosshrsth]

lgtm