mirrors/nats-server

Add support to customize leafnode ping_interval (#8718)

Addresses the Leafnodes part of #4991.

What

Adds ping_interval and ping_max as options in the leafnodes{} config block, independent from the global settings:

leafnodes {
  port: 7422
  ping_interval: '5s'
  ping_max: 6
}

This mirrors the existing route override from #5029 and the existing websocket.ping_interval override. Split out from the gateway PR to keep each change small and reviewable.

How

LeafNodeOpts.PingInterval / LeafNodeOpts.MaxPingsOut (opts.go), parsed in parseLeafNodes.
Wired through the same three call sites the route override uses in client.go: processPingTimer, setPingTimer, setFirstPingTimer.
No change needed in leafnode.go — unlike gateway/route, leafnode has no direct watchForStaleConnection call site to update.

Testing

Added TestLeafNodeCustomPing, modeled on TestRouteCustomPing. Verified it fails without the client.go wiring (ping never fires within the configured interval) and passes with it. Ran the full leafnode/parse-leaf/ config-check suite locally with no regressions.

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