Close hub subscriptions that cannot catch up - #71
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Replace the 100-block SOURCE_CHAN_SIZE limit with a 10000-block cap and a 30s catch-up timeout, so bursts on fast chains no longer close healthy subscriptions.
UlysseCorbeil
approved these changes
Sep 23, 2026
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Hub subscriptions were closed as soon as 100 blocks were waiting (
SOURCE_CHAN_SIZE). On a chain producing ~14 blocks/s, a ~15s pause from the live source is followed by a burst of ~200 blocks arriving within milliseconds, faster than a consumer can send the first one, so every subscriber was dropped at once even though each would have drained the burst in under a second.A subscription is now closed when:
SubscriptionCatchUpTimeout(default 30s). This catches a consumer that is stuck or slower than the chain, whatever the block rate, and closes it withErrSubscriptionBehind, which matchesErrSubscriptionChannelFullwitherrors.Isso substreams tier1 reconnects the same way.SubscriptionMaxBufferedBlocks(default 10000) blocks are waiting, to bound memory. Queued blocks are the same pointers the hub broadcasts to every subscriber, so the worst case is about that many blocks in total, not per subscriber.SOURCE_CHAN_SIZEis no longer read; firehose-core exposes both settings as flags.