RUST-2179 Ignore whether nodes are data-bearing when directConnection is true
#1334
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| .filter(|s| { | ||
| // If we're direct-connected or connected to a standalone, ignore whether the | ||
| // single server in the topology is data-bearing. | ||
| (self.topology_type == TopologyType::Single || s.server_type.is_data_bearing()) |
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The GetMore operation sets its selection criteria to a predicate, which meant that a direct connection to a hidden replica set member (which the driver gives server type RsOther) couldn't be selected here because it's not considered data-bearing. The fix here is to ignore whether a server is data-bearing if it's the only one in the topology. I didn't have much spec guidance to go off of here because, as far as I can tell, the predicate selection criteria variant is a rust-driver-specific thing. However, this server selection spec section indicates that the lone server in a single topology should always be selected.
It does still seem reasonable to filter out non-data-bearing servers when there are multiple servers in a topology so that, e.g., an arbiter isn't selected when a primary or secondary is also available.
RUST-2179, fixes #1332