Don't recalculate num pending inline on consumer info#7758
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neilalexander merged 2 commits intomainfrom Jan 23, 2026
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Don't recalculate num pending inline on consumer info#7758neilalexander merged 2 commits intomainfrom
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Signed-off-by: Neil Twigg <neil@nats.io>
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Signed-off-by: Maurice van Veen <github@mauricevanveen.com>
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| if o.sseq > state.LastSeq { | ||
| o.npc = 0 | ||
| } else if npc > 0 { | ||
| o.npc = int64(min(npc, state.Msgs, state.LastSeq-o.sseq+1)) |
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Updated from min(npc, state.Msgs) to min(npc, state.Msgs, state.LastSeq-o.sseq+1), which means:
- our pending count can't be larger than the total amount of available messages
- our pending count can't be larger than if every single message from our pointer to the end of the stream would be delivered
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…ithAccurateNumPending() This test demonstrates that when npc underflows (is too low due to double-decrement race): - info() returns wrong value (20) because checkNumPending() only caps, never recalculates - infoWithAccurateNumPending() returns correct value (50) because it always calls streamNumPending() Key insight: After PR nats-io#7758, checkNumPending() no longer triggers recalculation when npc is below state.Msgs. This means underflow scenarios (npc too low) are not detected/corrected by info(). For accurate monitoring, use infoWithAccurateNumPending(). https://claude.ai/code/session_011PV3TqBnngV6caLgFPdirH
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Recalculating num pending inline on consumer info can make them considerably more expensive than intended and can result in unexpectedly taking out the lock on the underlying store of the stream, creating contention with other resources.
We will now only make simple adjustments just to make sure that the numbers aren't completely unrealistic. Num pending calculations still take place when becoming leader or updating the subject filters in the consumer config.
Signed-off-by: Neil Twigg neil@nats.io