Mongos is reporting inconsistent information for sharded collections.

Our Setup:

A DB Cluster with three shards. Each shard has PSA Architecture. Three config servers.

Mongo Versions: 4.0.X

Scenario:

Mongos reports that collection alerts_20191026 is not sharded. But config.chunks reports that there are three chunks for that namespace that are in different shards

mongos> db.alerts_20191026.getShardDistribution()

Collection hitron.alerts_20191026 is not sharded.

mongos> use config

switched to db config

mongos> db.chunks.find({ns: "hitron.alerts_20191026"})

{ "_id" : "hitron.alerts_20191026-lineId_-3074457345618258602", "lastmod" : Timestamp(2, 0), "lastmodEpoch" : ObjectId("5da687c8a664d0a846cf713f"), "ns" : "hitron.alerts_20191026", "min" : \{ "lineId" : NumberLong("-3074457345618258602") }, "max" : { "lineId" : NumberLong("3074457345618258602") }, "shard" : "rs2", "history" : [ { "validAfter" : Timestamp(1571194825, 261), "shard" : "rs2" }, { "validAfter" : Timestamp(1571194824, 926), "shard" : "rs1" } ] }

{ "_id" : "hitron.alerts_20191026-lineId_3074457345618258602", "lastmod" : Timestamp(3, 0), "lastmodEpoch" : ObjectId("5da687c8a664d0a846cf713f"), "ns" : "hitron.alerts_20191026", "min" : \{ "lineId" : NumberLong("3074457345618258602") }, "max" : { "lineId" : { "$maxKey" : 1 } }, "shard" : "rs3", "history" : [ { "validAfter" : Timestamp(1571194825, 616), "shard" : "rs3" }, { "validAfter" : Timestamp(1571194824, 926), "shard" : "rs1" } ] }

{ "_id" : "hitron.alerts_20191026-lineId_MinKey", "lastmod" : Timestamp(3, 1), "lastmodEpoch" : ObjectId("5da687c8a664d0a846cf713f"), "ns" : "hitron.alerts_20191026", "min" : { "lineId" : { "$minKey" : 1 } }, "max" : { "lineId" : NumberLong("-3074457345618258602") }, "shard" : "rs1", "history" : [ { "validAfter" : Timestamp(1571194824, 926), "shard" : "rs1" } ] }

mongos> db.alerts_20191026.stats().nchunks
1

mongos> sh.status()

hitron.alerts_20191026
shard key: { "lineId" : "hashed" }
unique: false
balancing: true
chunks:
rs1 1
rs2 1
rs3 1
{ "lineId" : { "$minKey" : 1 } } -->> { "lineId" : NumberLong("-3074457345618258602") } on : rs1 Timestamp(3, 1)
{ "lineId" : NumberLong("-3074457345618258602") } -->> { "lineId" : NumberLong("3074457345618258602") } on : rs2 Timestamp(2, 0)
{ "lineId" : NumberLong("3074457345618258602") } -->> { "lineId" : { "$maxKey" : 1 } } on : rs3 Timestamp(3, 0)