Avoid serving validator endpoints while the node is far behind syncing head #7962
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…g head (non finality situations)
michaelsproul
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Aug 29, 2025
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LGTM. We need to be careful here, but I think this is safe enough for now as we have an escape hatch in case of liveness issues (--sync-tolerance-epochs).
jimmygchen
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jtraglia
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Sep 16, 2025
…g head (sigp#7962) A performance issue was discovered when devnet-3 was under non-finality - some of the lighthouse nodes are "stuck" with syncing because of handling proposer duties HTTP requests. These validator requests are higher priority than Status processing, and if they are taking a long time to process, the node won't be able to progress. What's worse is - under long period of non finality, the proposer duties calculation function tries to do state advance for a large number of [slots](https://github.com/sigp/lighthouse/blob/d545ddcbc7d97b24b5c15012d1a5f9a1dae90b2a/beacon_node/beacon_chain/src/beacon_proposer_cache.rs#L183) here, causing the node to spend all its CPU time on a task that doesn't really help, e.g. the computed duties aren't useful if the node is 20000 slots behind. To solve this issue, we use the `not_while_syncing` filter to prevent serving these requests, until the node is synced. This should allow the node to focus on sync under non-finality situations.
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Issue Addressed
A performance issue was discovered when devnet-3 was under non-finality - some of the lighthouse nodes are "stuck" with syncing because of handling proposer duties HTTP requests.
These validator requests are higher priority than Status processing, and if they are taking a long time to process, the node won't be able to progress. What's worse is - under long period of non finality, the proposer duties calculation function tries to do state advance for a large number of slots here, causing the node to spend all its CPU time on a task that doesn't really help, e.g. the computed duties aren't useful if the node is 20000 slots behind.
To solve this issue, we use the
not_while_syncingfilter to prevent serving these requests, until the node is synced. This should allow the node to focus on sync under non-finality situations.