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Improve the reliability of the refresh process due to the loss of slots #52

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Oct 20, 2023
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Improve the reliability of the refresh process due to the loss of slots #52

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8641598
Improve the reliability of the refresh process due to the loss of slo…
Oct 15, 2023
5fcedd2
Fix getting addrs on method refresh does not work as expected
Oct 19, 2023
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8 changes: 7 additions & 1 deletion cluster.go
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Original file line number Diff line number Diff line change
Expand Up @@ -106,7 +106,13 @@ func (c *Cluster) refresh(bg bool) error {
var errMsgs []string
var oldm, newm [HashSlots][]string

addrs, _ := c.getNodeAddrs(false)
// get all node addrs, including replicas
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Note that this does not return all node addresses, it will return the replicas if it knows about any, otherwise the masters. I'm not sure I like switching the refresh to get cluster slots from replicas - it should be ok, but it might need a READONLY call to make the replica accept the command (I'm not sure since this is not serving a key, it's an administration command), we'd have to test that and it might differ based on redis version...

I'll come back to review it when I have a bit more time to get back in context, but I think we should address that in getNodeAddrs instead and reuse the StartupNodes only if both c.masters and c.replicas are empty, and here in refresh fall back to using the replicas only if getNodeAddrs(false) returns an empty list of addresses.

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here in refresh fall back to using the replicas only if getNodeAddrs(false) returns an empty list of addresses.

And making sure the replicas do serve the CLUSTER SLOTS command without a READONLY request first.

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@ljfuyuan ljfuyuan Oct 16, 2023 •
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Indeed, I made the mistake of getNodeAddrs(true) will not return all nodes.

And making sure the replicas do serve the CLUSTER SLOTS command without a READONLY request first

I did tests on redis 5.0.8 and 6.2.13 clusters. The replica node can correctly return cluster slots information without READONLY

So, based on the above, can we try to do this? At the same time, the semantics of preferReplicas can be preserved .

        addrs, _ := c.getNodeAddrs(false)
	if len(addrs) == 0 {
		if addrs, _ = c.getNodeAddrs(true); len(addrs) == 0 {
			addrs = c.StartupNodes
		}
	}

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Yes, I think that would be good.

addrs, _ := c.getNodeAddrs(true)
// when addrs cannot be obtained, StartupNodes is always used to populate
if len(addrs) == 0 {
addrs = c.StartupNodes
}

for _, addr := range addrs {
m, err := c.getClusterSlots(addr)
if err != nil {
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