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cmd/devp2p: close the iterator in discv4 LookupRandom - #35206
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The LookupRandom RPC handler obtains a node iterator from RandomNodes() but never closes it. RandomNodes returns a lookupIterator backed by a cancelable context derived from the listener's lifetime context, so each call leaks the cancel func (and any in-flight lookup) until the discv4 listener shuts down. When the listener serves the RPC API it is long-lived, so repeated LookupRandom calls accumulate the leak. Close the iterator when the handler returns, matching how the crawler releases the same RandomNodes iterators.
rjl493456442
approved these changes
Jun 30, 2026
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The `LookupRandom` RPC handler obtains a node iterator from `RandomNodes()` but never closes it.
`RandomNodes()` returns a `lookupIterator` backed by a cancelable context derived from the listener's lifetime context (`newLookupIterator` -> `context.WithCancel`). The iterator's `Close()` is what calls the cancel func, so each `LookupRandom` call that never closes leaks the cancel func (and any in-flight lookup goroutine) until the discv4 listener shuts down. When the listener serves the RPC API (`discv4 --rpc`) it is long-lived, so repeated `LookupRandom` calls accumulate the leak.
Close the iterator when the handler returns. This matches how the crawler already releases the same `RandomNodes()` iterators (`crawl.go` closes every iterator it consumes).