need to handle command object variant
cmd: { "query" : { [js_test:basic2] 2017-07-20T16:29:50.439-0400 "count" : "basic2", [js_test:basic2] 2017-07-20T16:29:50.439-0400 "query" : { [js_test:basic2] 2017-07-20T16:29:50.439-0400 [js_test:basic2] 2017-07-20T16:29:50.440-0400 }, [js_test:basic2] 2017-07-20T16:29:50.440-0400 "fields" : { [js_test:basic2] 2017-07-20T16:29:50.440-0400 [js_test:basic2] 2017-07-20T16:29:50.440-0400 }, [js_test:basic2] 2017-07-20T16:29:50.440-0400 "readConcern" : { [js_test:basic2] 2017-07-20T16:29:50.440-0400 "afterClusterTime" : Timestamp(1500582590, 4), [js_test:basic2] 2017-07-20T16:29:50.440-0400 "level" : "local" [js_test:basic2] 2017-07-20T16:29:50.441-0400 } [js_test:basic2] 2017-07-20T16:29:50.441-0400 }, [js_test:basic2] 2017-07-20T16:29:50.441-0400 "$readPreference" : { [js_test:basic2] 2017-07-20T16:29:50.441-0400 "mode" : "secondary" [js_test:basic2] 2017-07-20T16:29:50.441-0400 } [js_test:basic2] 2017-07-20T16:29:50.441-0400 }
i.e the readConcern needs to be inside the "query" or "$query" commands