The node-engine's bus watch never holds the client back (issue 1966, bootstrap recovery) #210

Merged

mesh-tools merged 2 commits from fix/1966-watch-never-blocks into main 2026-11-07 23:40:49 +00:00

Conversation 1 Commits 2 Files Changed 4

+148 -33

2 Commits

Author	SHA1	Message	Date
jschoubben	4f1e92160a	Round 1: the pin tests merged (test budget), KVWatch's doc says what folds ... The review of fe9533c1: a new test function raised a count already over the budget, so two broker-pin tests are one; KVWatch no longer yields every change, and its doc says so (issue 1966). Claude-Session: https://claude.ai/code/session_01NcbgfFfQ4Z9UE5jK32PmE5	2026-11-08 00:38:36 +01:00
jschoubben	fe9533c186	The node-engine's bus watch never holds the client back: it keeps the newest update per key while its reader is busy (issue 1966) ... Live fault 2026-11-08: node-engines on two machines logged only "nats: slow consumer, messages dropped" and applied nothing. The client's watch sends into its channel from inside the subscription's callback; KVWatch forwarded that channel to its reader blocking, and the reader (composing for minutes) stopped draining, so the subscription's pending limit overflowed. Quick fix: a larger buffer on the watch's channel; it only moves the limit. Thorough fix (chosen): the forwarder always drains the client's channel and, while its reader is busy, coalesces the pending updates by key (newest value and revision, first-seen order, Caught kept in its place), so no reader's pace can back the client up, whatever the burst. A slow consumer error now names its subscription and what it holds pending. Claude-Session: https://claude.ai/code/session_01NcbgfFfQ4Z9UE5jK32PmE5	2026-11-08 00:26:33 +01:00