If mongos is committed to matching the drivers Server Selection Spec, it needs to be updated to match behavior we decided on for drivers last year. See this section of the Server Selection Spec:
mongos should obey the "$readPreference" document sent with any command, regardless of the command name. The "whitelist" from the old Read Preferences spec is superseded by the new, simpler Server Selection Spec behavior.
- is related to
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SERVER-29407 BadValue error when passing readPreference option to usersInfo on a mongos only
- Closed
- related to
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SERVER-22515 Implement Server Selection Spec's changes for runCommand and command helpers
- Closed