[Flight] Skip transferReferencedDebugInfo during debug info resolution - #35795
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When the Flight Client resolves chunk references during model parsing, it calls `transferReferencedDebugInfo` to propagate debug info entries from referenced chunks to the parent chunk. Debug info on chunks is later moved to their resolved values, where it is used by React DevTools to show performance tracks and what a component was suspended by. Debug chunks themselves (specifically `ReactComponentInfo`, `ReactAsyncInfo`, `ReactIOInfo`, and their outlined references) are metadata that is never rendered. They don't need debug info attached to them. Without this fix, debug info entries accumulate on outlined debug chunks via their references to other debug chunks (e.g. owner chains and props deduplication paths). Since each outlined chunk's accumulated entries are copied to every chunk that references it, this creates exponential growth in deep component trees, which can cause the dev server to hang and run out of memory. This generalizes the existing skip of `transferReferencedDebugInfo` for Element owner/stack references (which already recognizes that references to debug chunks don't need debug info transferred) to all references resolved during debug info resolution. It adds an `isInitializingDebugInfo` flag set in `initializeDebugChunk` and `resolveIOInfo`, which propagates through all nested `initializeModelChunk` calls within the same synchronous stack. For the async path, `waitForReference` captures the flag at call time into `InitializationReference.isDebug`, so deferred fulfillments also skip the transfer.
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| }; | ||
| let initializingHandler: null | InitializationHandler = null; | ||
| let initializingChunk: null | BlockedChunk<any> = null; | ||
| let isInitializingDebugInfo: boolean = false; |
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Should this be stashed on the initialization handler? We’d never assign the property so it shouldn’t create more hidden classes in practice
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That won't work, because initializeModelChunk resets initializingHandler = null, so the flag would be lost in nested calls.
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The Flight Client copies the debug info of a referenced chunk into the chunk that references it, so that the receiving chunk records what blocked it. It copies the entries once per reference, and a referenced chunk already carries the entries that it received itself. A response that deduplicates the same object across a chain of rows therefore multiplies the entries at every step. In development the array eventually grows past what the engine can allocate for it, and the client throws `RangeError: Invalid array length`. The receiving chunk now takes each entry only once. The entries are copied by reference and never cloned on this path, so a comparison by identity is exact. The array becomes bounded by the number of distinct entries in the response rather than by a chosen limit. The bookkeeping costs one `Set` per chunk that receives debug info, in development only. The set holds a reference to each entry rather than a copy, so the entries stay shared and nothing about the debug info is duplicated. A chunk receives entries only while it is blocked, so the fix releases the set as soon as the chunk initializes. Debug info still accumulates transitively, which this change does not alter. This change also adds the `!reference.isDebug` guards that react#37358 proposes for the element props branch and the default branch of `fulfillReference`. react#35795 introduced the rule that a reference resolved during debug info resolution does not transfer, and it left those two branches behind. The guards make that rule hold at every branch. However, those branches reference debug chunks that carry no entries, so the guards change no observed behaviour, and they do not fix the growth in react#37343, which comes from references in model chunks. react#37343 also reports the call in `getOutlinedModel` as unguarded, which it is not, because react#35795 already skips it there. The rest of react#37358 deduplicates the entries, which is the right direction, but it scans the receiving array for every candidate, which is quadratic in the size of the debug info. react#37359 caps the array at a constant instead, which stops the crash but keeps copying the duplicates and drops debug info once a response passes the cap. Alternatives Considered - Tracking the referenced chunks rather than the entries would be cheaper, because it would need one map entry per referenced chunk. It would not be enough, because a chunk can reach the same entry through two paths. A chunk can hold a client reference directly and also reference a chunk that already received the debug info of that client reference. - Recording the last receiving chunk on each entry would be exact while a chunk parses its model, where the transfers into it are consecutive. It would break once transfers into different chunks interleave, and that is the path the reported crash takes. - Turning `_debugInfo` itself into a `Set` is not possible, because the reconciler, Fizz, the Flight Server and DevTools read it by index and depend on its order. Fixes react#37343 Closes react#37358 Closes react#37359 Co-authored-by: sundeep8967 <71071718+sundeep8967@users.noreply.github.com>
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The Flight Client copies the debug info of a referenced chunk into the chunk that references it, so that the receiving chunk records what blocked it. It copies the entries once per reference, and a referenced chunk already carries the entries that it received itself. A response that deduplicates the same object across a chain of rows therefore multiplies the entries at every step. In development the array eventually grows past what the engine can allocate for it, and the client throws `RangeError: Invalid array length`. The receiving chunk now takes each entry only once. The entries are copied by reference and never cloned on this path, so a comparison by identity is exact. The array becomes bounded by the number of distinct entries in the response rather than by a chosen limit. The bookkeeping costs one `Set` per chunk that receives debug info, in development only. The set holds a reference to each entry rather than a copy, so the entries stay shared and nothing about the debug info is duplicated. A chunk receives entries only while it is blocked, so the fix releases the set as soon as the chunk initializes. Debug info still accumulates transitively, which this change does not alter. This change also adds the `!reference.isDebug` guards that #37358 proposes for the element props branch and the default branch of `fulfillReference`. #35795 introduced the rule that a reference resolved during debug info resolution does not transfer, and it left those two branches behind. The guards make that rule hold at every branch. However, those branches reference debug chunks that carry no entries, so the guards change no observed behaviour, and they do not fix the growth in #37343, which comes from references in model chunks. #37343 also reports the call in `getOutlinedModel` as unguarded, which it is not, because #35795 already skips it there. The rest of #37358 deduplicates the entries, which is the right direction, but it scans the receiving array for every candidate, which is quadratic in the size of the debug info. #37359 caps the array at a constant instead, which stops the crash but keeps copying the duplicates and drops debug info once a response passes the cap. **Alternatives Considered** - Tracking the referenced chunks rather than the entries would be cheaper, because it would need one map entry per referenced chunk. It would not be enough, because a chunk can reach the same entry through two paths. A chunk can hold a client reference directly and also reference a chunk that already received the debug info of that client reference. - Recording the last receiving chunk on each entry would be exact while a chunk parses its model, where the transfers into it are consecutive. It would break once transfers into different chunks interleave, and that is the path the reported crash takes. - Turning `_debugInfo` itself into a `Set` is not possible, because the reconciler, Fizz, the Flight Server and DevTools read it by index and depend on its order. Fixes #37343 Closes #37358 Closes #37359 Co-authored-by: sundeep8967 <71071718+sundeep8967@users.noreply.github.com>
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The Flight Client copies the debug info of a referenced chunk into the chunk that references it, so that the receiving chunk records what blocked it. It copies the entries once per reference, and a referenced chunk already carries the entries that it received itself. A response that deduplicates the same object across a chain of rows therefore multiplies the entries at every step. In development the array eventually grows past what the engine can allocate for it, and the client throws `RangeError: Invalid array length`. The receiving chunk now takes each entry only once. The entries are copied by reference and never cloned on this path, so a comparison by identity is exact. The array becomes bounded by the number of distinct entries in the response rather than by a chosen limit. The bookkeeping costs one `Set` per chunk that receives debug info, in development only. The set holds a reference to each entry rather than a copy, so the entries stay shared and nothing about the debug info is duplicated. A chunk receives entries only while it is blocked, so the fix releases the set as soon as the chunk initializes. Debug info still accumulates transitively, which this change does not alter. This change also adds the `!reference.isDebug` guards that #37358 proposes for the element props branch and the default branch of `fulfillReference`. #35795 introduced the rule that a reference resolved during debug info resolution does not transfer, and it left those two branches behind. The guards make that rule hold at every branch. However, those branches reference debug chunks that carry no entries, so the guards change no observed behaviour, and they do not fix the growth in #37343, which comes from references in model chunks. #37343 also reports the call in `getOutlinedModel` as unguarded, which it is not, because #35795 already skips it there. The rest of #37358 deduplicates the entries, which is the right direction, but it scans the receiving array for every candidate, which is quadratic in the size of the debug info. #37359 caps the array at a constant instead, which stops the crash but keeps copying the duplicates and drops debug info once a response passes the cap. **Alternatives Considered** - Tracking the referenced chunks rather than the entries would be cheaper, because it would need one map entry per referenced chunk. It would not be enough, because a chunk can reach the same entry through two paths. A chunk can hold a client reference directly and also reference a chunk that already received the debug info of that client reference. - Recording the last receiving chunk on each entry would be exact while a chunk parses its model, where the transfers into it are consecutive. It would break once transfers into different chunks interleave, and that is the path the reported crash takes. - Turning `_debugInfo` itself into a `Set` is not possible, because the reconciler, Fizz, the Flight Server and DevTools read it by index and depend on its order. Fixes #37343 Closes #37358 Closes #37359 Co-authored-by: sundeep8967 <71071718+sundeep8967@users.noreply.github.com> DiffTrain build for [8f00437](8f00437)
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When the Flight Client resolves chunk references during model parsing, it calls
transferReferencedDebugInfoto propagate debug info entries from referenced chunks to the parent chunk. Debug info on chunks is later moved to their resolved values, where it is used by React DevTools to show performance tracks and what a component was suspended by.Debug chunks themselves (specifically
ReactComponentInfo,ReactAsyncInfo,ReactIOInfo, and their outlined references) are metadata that is never rendered. They don't need debug info attached to them. Without this fix, debug info entries accumulate on outlined debug chunks via their references to other debug chunks (e.g. owner chains and props deduplication paths). Since each outlined chunk's accumulated entries are copied to every chunk that references it, this creates exponential growth in deep component trees, which can cause the dev server to hang and run out of memory.This generalizes the existing skip of
transferReferencedDebugInfofor Element owner/stack references (which already recognizes that references to debug chunks don't need debug info transferred) to all references resolved during debug info resolution. It adds anisInitializingDebugInfoflag set ininitializeDebugChunkandresolveIOInfo, which propagates through all nestedinitializeModelChunkcalls within the same synchronous stack. For the async path,waitForReferencecaptures the flag at call time intoInitializationReference.isDebug, so deferred fulfillments also skip the transfer.