simplify session dependent tasks and add TTL support#91729
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bgw
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Please update turbo-tasks/function.md with information about the new parameter
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This reverts commit fe99f0d.
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#92320) This is causing OOMs in some applications running with a persistent cache See discussion: https://vercel.slack.com/archives/C03EWR7LGEN/p1775159630054759 The issue appears to be invalidating the chunk graph in an odd way that causes us to allocate an ~infinite number of error strings
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Summary
Three related improvements to turbo-tasks session-dependent task handling:
1. Make
session_dependenta function attributePreviously, tasks called
mark_session_dependent()at runtime to flag themselves. This PR makes it a compile-time#[turbo_tasks::function(session_dependent)]attribute instead. Benefits:mark_session_dependent()call needed — the attribute is declarative and statically checked.mark_session_dependent(),mark_own_task_as_session_dependent(), and thesession_dependentfield fromInProgressStateInner. The backend now readsis_session_dependentdirectly from theNativeFunctionmetadata viaTaskGuard::is_session_dependent().2. Fix fetch to respect HTTP
Cache-ControlheadersPreviously,
fetchresults were cached indefinitely meaning results would never be refreshed (unless the cache was invalidated). Now they aresession_dependentwith a TTL to ensure we respect the http settings (e.g. Google Fonts withmax-age=86400).New two-task pattern:
fetch_inner( NOTsession_dependent): Performs the HTTP request, grabs anInvalidatorfor itself, and returns the response + invalidator + absolute deadline. Cached across sessions.fetch(network,session_dependent): Reads the cachedfetch_innerresult and spawns a timer to invalidate when the TTL expires.On warm cache restore,
fetchre-executes (session-dependent), reads the persisted deadline fromfetch_inner's cached result, computes remaining TTL, and spawns a timer — no HTTP request unless the TTL has already expired. Mid-session, the timer fires and triggers a re-fetch.Error handling: On fetch failure,
fetch_innertakes a dependency onCompletion::session_dependent()so transient errors (network down, DNS failure) are retried on the next session without busy-looping.3. Drop
TransientStatein favor of inline solutionTransientStatewas only used in one place (EcmascriptModuleAsset::last_successful_parse) and brought unnecessary complexity — it registered invalidators and calledmark_session_dependent()on every read. Replaced with a simpleTransientCache<T>local toturbopack-ecmascriptthat is just aMutex<Option<T>>with#[bincode(skip)].Test Plan
turbo-tasks-fetch/tests/fetch.rs:ttl_invalidates_within_session— mock server returnsmax-age=1, body changes, verifies re-fetch after TTLttl_invalidates_on_session_restore— fetches with TTL, stops TT, waits for expiry, warm restores with new TT, verifies re-fetcherrors_retried_on_session_restore— server returns 500, stops TT, fixes server, warm restores, verifies successcargo check -p turbo-tasks -p turbo-tasks-backend -p turbo-tasks-fetch