Summary#

Avoiding React state updates after unmount

Problem#

Async work started in a React component may resolve after the component unmounts, causing warnings like "Can't perform a React state update on an unmounted component."

Solution#

In useEffect, add cleanup logic. Use a local mutable flag or, preferably for cancellable APIs, an AbortController/cancellation mechanism. Before calling setState from an async callback, verify the component is still mounted or the request has not been aborted.

Failure Modes#

• Starting async operations in useEffect without cleanup can update stale/unmounted components.
• Using an isMounted flag incorrectly across renders can create stale-closure bugs; keep it scoped to the effect.
• Ignoring dependency arrays can cause repeated async work or missed updates.

Sources#

• https://stackoverflow.com/questions/72084607/what-are-the-best-practices-for-testing-a-fastapi-project-with-jwt-authenticatio
• https://stackoverflow.com/questions/63918342/refresh-token-using-fastapi-and-swagger
• https://stackoverflow.com/questions/53949393/cant-perform-a-react-state-update-on-an-unmounted-component
• https://stackoverflow.com/questions/57960894/kubernetes-deployment-failure-how-to-inspect
• https://stackoverflow.com/questions/54107445/kubernetes-deployment-failing-due-to-image-pull-failure
• https://stackoverflow.com/questions/47536536/whats-the-difference-between-docker-compose-and-kubernetes
• https://stackoverflow.com/questions/37685581/how-to-get-docker-compose-to-use-the-latest-image-from-the-repository
• https://stackoverflow.com/questions/37521440/is-docker-compose-suitable-for-production
• https://stackoverflow.com/questions/60856050/disable-postgresql-query-optimization
• https://stackoverflow.com/questions/27409413/query-optimization-for-postgresql
• mined_at: 2026-09-26T02:42:47Z

Sagwan Revalidation 2026-09-26T03:16:31Z#

• verdict: refresh
• note: React 18 경고 변화와 오염된 출처 목록 때문에 갱신 가치가 있음

Sagwan Revalidation 2026-09-28T23:31:44Z#

• verdict: refresh
• note: React 18부터 해당 경고가 제거됐고 무관한 출처가 섞여 있어 수정이 필요함.

Sagwan Revalidation 2026-10-03T04:09:23Z#

• verdict: refresh
• note: React 18에서 언마운트 후 상태 업데이트 경고가 제거됐고, 출처에도 무관한 링크가 섞여 있습니다.

Sagwan Revalidation 2026-10-06T04:17:04Z#

• verdict: refresh
• note: React 18에서 해당 경고가 제거됐고, 무관한 출처가 섞여 있어 수정이 필요합니다.

Sagwan Revalidation 2026-10-09T03:19:49Z#

• verdict: refresh
• note: React 18에서 해당 경고가 제거됐고 무관한 출처가 섞여 있어 수정이 필요합니다.

Sagwan Revalidation 2026-10-11T20:05:34Z#

• verdict: refresh
• note: React 18부터 해당 경고가 제거됐고, 무관한 출처가 섞여 있어 수정이 필요합니다.

Sagwan Revalidation 2026-10-14T15:23:51Z#

• verdict: refresh
• note: React 18부터 해당 경고가 제거됐고, 무관한 출처가 섞여 있어 수정이 필요합니다.

Sagwan Revalidation 2026-10-17T12:38:56Z#

• verdict: refresh
• note: React 18에서 해당 경고가 제거됐고 출처에 무관한 링크가 많아 수정할 가치가 있습니다.

Sagwan Revalidation 2026-10-20T08:07:23Z#

• verdict: refresh
• note: React 18 이후 언마운트 경고 설명이 낡았고, 무관한 출처 링크가 섞여 있어 수정이 필요합니다.