Having a sharded cluster in production which has been running for a good year now without issues. Everything is on 4.0, classic 3-3-3(config) + 2 mongos.

While revisiting our back-up strategy i stumped upon this step.

I tried finding that value on every node (mongos, primaries, secondaries) and none of them have a shardIdentity.

mongos> db.system.version.find()
{ "_id" : "featureCompatibilityVersion", "version" : "4.0" }
{ "_id" : "authSchema", "currentVersion" : 5 }

This thing looks important and is part of STARTUP2 phase.

For the sake of testing and documenting our back-ups, i followed all the steps from the "Restore Sharded Cluster" documentation. At the end of it:

  • sh.status() is looking good, i'm seeing the shards
  • rs.status() is also good
  • A standalone mongod gives me the proper stats on restored data
  • mongod output seems fine..

But then db.coll.stats() fails with :

        "ok" : 0,
        "errmsg" : "Cannot accept sharding commands if sharding state has not been initialized with a shardIdentity document",
        "code" : 203,
        "codeName" : "ShardingStateNotInitialized",
        "operationTime" : Timestamp(1548184216, 1),
        "$clusterTime" : {
                "clusterTime" : Timestamp(1548184216, 1),
                "signature" : {
                        "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
                        "keyId" : NumberLong(0)

And i can see this error from mongod:

I CONTROL [LogicalSessionCacheReap] Sessions collection is not set up; waiting until next sessions reap interval: sharding state is not yet initialized

So far i tried:

  • sh.enableSharding() returns true (1) but doesn't change anything
  • Been through https://github.com/mongodb/mongo/wiki/Sharding-Internals#sharding-component-initialization
  • Double checked on our production cluster and no shardIdentity there.

So, how does one enforce a shardIdentify or generate one? How do you find out the "shard name" because i couldn't find such a thing. And, well, why would sh.status() give the proper result but cannot associate its shards with the current data?



At first I didn't want to mess around with the admin database but it seemed it was the only thing to do.

Gather information

sh.status() on a mongos will give the shards name needed and the shard cluster id. Something like that:

"clusterId" : ObjectId("3b743bf3134df1f277980ard")
        {  "_id" : "shardname1",  "host" : "[host:port]",  "state" : 1 }
        {  "_id" : "shardname2",  "host" : "[host:port]",  "state" : 1 }

For each replica set

  • Get on the primary, select the admin database


    "_id" : "shardIdentity",
    "clusterId" : ObjectId("3b743bf3134df1f277980ard"),
    "shardName" : "REPLICA_SHARD_NAME",
    "configsvrConnectionString" : "conf/[host]"

See Shard Aware.

  • Reboot all replica set members

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.