How to Verify Sharding? - mongodb

Question

I am trying to shard MongoDB. I am done with Sharding configuration, but I am not sure how to verify if sharding is functional.
How do i check whether my data is get sharded? Is there a query to verify/validate the shards?

Answer 1

You can also execute a simple command on your mongos router :
> use admin
> db.printShardingStatus();
which should output informations about your shards, your sharded dbs and your sharded collection as mentioned in the mongodb documentation
sharding version: { "_id" : 1, "version" : 2 }
shards:
{ "_id" : ObjectId("4bd9ae3e0a2e26420e556876"), "host" : "localhost:30001" }
{ "_id" : ObjectId("4bd9ae420a2e26420e556877"), "host" : "localhost:30002" }
{ "_id" : ObjectId("4bd9ae460a2e26420e556878"), "host" : "localhost:30003" }
databases:
{ "name" : "admin", "partitioned" : false,
"primary" : "localhost:20001",
"_id" : ObjectId("4bd9add2c0302e394c6844b6") }
my chunks
{ "name" : "foo", "partitioned" : true,
"primary" : "localhost:30002",
"sharded" : { "foo.foo" : { "key" : { "_id" : 1 }, "unique" : false } },
"_id" : ObjectId("4bd9ae60c0302e394c6844b7") }
my chunks
foo.foo { "_id" : { $minKey : 1 } } -->> { "_id" : { $maxKey : 1 } }
on : localhost:30002 { "t" : 1272557259000, "i" : 1 }

Answer 2

MongoDB has detailed documentation on Sharding here ...
http://www.mongodb.org/display/DOCS/Sharding+Introduction
To anwser you question (I think), see the portion on the config Servers ...
Each config server has a complete copy
of all chunk information. A two-phase
commit is used to ensure the
consistency of the configuration data
among the config servers.
Basically, it is the config server's job to make sure everything get sharded ... correctly.
Also, there are system collections you can query ...
db.runCommand( { listshards : 1 } );
Lots of help in the prez below too ...
http://www.slideshare.net/mongodb/mongodb-sharding-internals
http://www.10gen.com/video/mongosv2010/sharding

Answer 3

If you just want to check whether you are conencted to a sharded cluster or not:
db.isMaster() can be used to detect that you are connected to a sharding router (mongos).
If db.isMaster().msg is "isdbgrid", you are connected to a sharded instance.
db.isMaster() can be run without authentication.
For checking the details of the shards, sh.status() also works, which has the same output as db.printShardingStatus(); works.