CODEWITHSUNDEEP
mongodbsharding
Florent Constant
Florent Constant

Reputation: 1

MongoDB error when sharding a collection: ns not found

I've setup a simple server configuration for testing sharding functionnalities purpose and i get the error above.

My configuration is pretty simple: one config server, one shard server and one mongos (respectively in 127.0.0.1:27019, 127.0.0.1:27018, 127.0.0.1:27017).

Everything looks to work well until i try to shard a collection, the command gives me the following:

sh.shardCollection("test.test", { "test" : 1 } )
{
    "ok" : 0,
    "errmsg" : "ns not found",
    "code" : 26,
    "codeName" : "NamespaceNotFound",
    "operationTime" : Timestamp(1590244259, 5),
    "$clusterTime" : {
        "clusterTime" : Timestamp(1590244259, 5),
        "signature" : {
            "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
            "keyId" : NumberLong(0)
        }
    }
}

The config server and shard server outputs show no errors:

2020-05-23T10:39:46.629-0400 I  SHARDING [conn11] about to log metadata event into changelog: { _id: "florent-Nitro-AN515-53:27018-2020-05-23T10:39:46.629-0400-5ec935b2bec982e313743b1a", server: "florent-Nitro-AN515-53:27018", shard: "rs0", clientAddr: "127.0.0.1:58242", time: new Date(1590244786629), what: "shardCollection.start", ns: "test.test", details: { shardKey: { test: 1.0 }, collection: "test.test", uuid: UUID("152add6f-e56b-40c4-954c-378920eceede"), empty: false, fromMapReduce: false, primary: "rs0:rs0/127.0.0.1:27018", numChunks: 1 } }

2020-05-23T10:39:46.620-0400 I  SHARDING [conn25] distributed lock 'test' acquired for 'shardCollection', ts : 5ec935b235505bcc59eb60c5
2020-05-23T10:39:46.622-0400 I  SHARDING [conn25] distributed lock 'test.test' acquired for 'shardCollection', ts : 5ec935b235505bcc59eb60c7
2020-05-23T10:39:46.637-0400 I  SHARDING [conn25] distributed lock with ts: 5ec935b235505bcc59eb60c7' unlocked.
2020-05-23T10:39:46.640-0400 I  SHARDING [conn25] distributed lock with ts: 5ec935b235505bcc59eb60c5' unlocked.

Of course the collection exists on primary shard:

rs0:PRIMARY> db.test.stats()
{
    "ns" : "test.test",
    "size" : 216,
    "count" : 6,
    "avgObjSize" : 36,
    "storageSize" : 36864,
    "capped" : false,
    ...
}

I have no idea what could be wrong here, i'd much appreciate any help :)

EDIT:

Here is the detail about steps i follom to run servers, i probably misunderstand something :

Config server:

sudo mongod --configsvr --replSet rs0 --port 27019 --dbpath /srv/mongodb/cfg  
mongo --port 27019

Then in mongo shell

rs.initiate(
  {
    _id: "rs0",
    configsvr: true,
    members: [
      { _id : 0, host : "127.0.0.1:27019" }
    ]
  }
)

Sharded server:

sudo mongod --shardsvr --replSet rs0  --dbpath /srv/mongodb/shrd1/ --port 27018
mongo --port 27018

Then in shell:

rs.initiate(
  {
    _id: "rs0",
    members: [
      { _id : 0, host : "127.0.0.1:27018" }
    ]
  }
)
db.test.createIndex({test:1})

Router:

sudo mongos --configdb rs0/127.0.0.1:27019
mongo

Then in shell:

sh.addShard('127.0.0.1:27018')
sh.enableSharding('test')
sh.shardCollection('test.test', {test:1})

Upvotes: 0

Views: 2904

Answers (2)

Florent Constant
Florent Constant

Reputation: 1

I just misunderstood one base concept: config servers and shard servers are distinct and independant mongodb instances, so each must be part of distinct replicasets .

So replacing

sudo mongod --configsvr --replSet rs0 --port 27019 --dbpath /srv/mongodb/cfg

with

sudo mongod --configsvr --replSet rs0Config --port 27019 --dbpath /srv/mongodb/cfg

makes the configuration work.

Upvotes: 0

D. SM
D. SM

Reputation: 14520

That error happens sometimes when some routers have out of date ideas of what databases/collections exist in the sharded cluster.

Try running https://docs.mongodb.com/manual/reference/command/flushRouterConfig/ on each mongos (i.e. connect to each mongos sequentially by itself and run this command on it).

Upvotes: 2

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