transport: use go 1.19 atomic.Pointer instead of atomic.Value #284
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transport/cluster.go
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| @@ -443,7 +443,7 @@ func parseTokensFromRow(n *Node, r frame.Row, ring *Ring) error { | |||
| } | |||
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| func (c *Cluster) Topology() *topology { | |||
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Is Topology() method still necessary? It is an exported method returning non-exported type, so I wonder if we could just remove it in favor of using c.topology.Load() directly.
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Topology() is used in session to get all nodes to prepare a query on them. Nodes are the only field of topology that is currently exported and used outside of transport, so I suppose Topology() could be removed and replaced with just func (*Cluster) Nodes().
The other thing is that topology is passed inside QueryInfo to host selection policies, but same as all fields of QueryInfo, it is unexported. It likely should be accessible outside of transport, opened #287 about it, it may influence if topology will be exported.
The point of Topology() and setTopology() cluster methods was to give some sort of type safety as topology was an atomic.Value that can hold any type. As topology is now an atomic.Pointer they are no longer needed. Session sometimes needs to perform a query on all nodes of the cluster, to allow that cluster now has an exported Nodes() method.
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Currently transport package atomically replaces topology and connections with new ones. This is done using atomic.Value that hold topology and conn pointers, this is not type-safe and requires type assertions every time the driver needs the values hidden in atomic.Value.
Go 1.19 introduces a generic atomic.Pointer[T], that is a more suitable replacement, adding type-safety and removing the type assertions,
This PR replaces mentioned atomic.Values with the new generic atomic pointer type.
Fixes #269