Mongodb – How to properly use moveChunk when chunks of certain range needs to be moved

mongodbmongodb-3.6mongorestoresharding

A MongoDB 3.6.3 database has two shards and a mongodump file with partial data of one collection needs to be restored. The first shard is named "fast" while second "slow". The idea is to restore the dump to the "slow" shard. According to sharding rules the data should go to the "slow" shard, but it actually goes to the wrong one when restore is tried.

Before restoring the data, I want to manually move a range of chunks from fast to slow shard, but are unable to properly issue the command. All examples found are showing of moving only one exact chunk. _id is used as a sharding key.

Try 1:

use admin
db.runCommand({ moveChunk: "db.use", bounds : [ {_id : ObjectId("58b60e73e5d4e7019aa2be17")}, {_id : ObjectId("58bca60f5067031c77b03807")} ], to: "rs1" })

This is the response:

{
        "ok" : 0,
        "errmsg" : "no chunk found with the shard key bounds [{ _id: ObjectId('58b60e73e5d4e7019aa2be17') }, { _id: ObjectId('58bca60f5067031c77b03807') })",
        "$clusterTime" : {
                "clusterTime" : Timestamp(1523459407, 14673),
                "signature" : {
                        "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
                        "keyId" : NumberLong(0)
                }
        },
        "operationTime" : Timestamp(1523459407, 14673)
}

Try 2:

sh.moveChunk("db.use", {_id:{$gt: ObjectId("58b60e73e5d4e7019aa2be17"), $lt: ObjectId("58bca60f5067031c77b03807") }},"rs1")

Response:

{
        "ok" : 0,
        "errmsg" : "no shard key found in chunk query { _id: { $gt: ObjectId('58b60e73e5d4e7019aa2be17'), $lt: ObjectId('58bca60f5067031c77b03807') } }",
        "$clusterTime" : {
                "clusterTime" : Timestamp(1523460271, 11742),
                "signature" : {
                        "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
                        "keyId" : NumberLong(0)
                }
        },
        "operationTime" : Timestamp(1523460271, 11742)
}

Any idea how to move chunks that belong to certain shard key range?

Best Answer

Until a more decent way is found, I used this script solution:

use config
sh.stopBalancer()
var lower=ObjectId("58B60F00e4b03547ad945a8a");
var upper=ObjectId("58BCA680e4b03547ad945a8a");
var query={shard: "rs0", ns: "db.use", "max._id":{$gte: lower}, "min._id": {$lte: upper}};
var cursor=db.chunks.find(query);

cursor.forEach(function(d) {
 print( "chunk: " + d.min._id ); 
 sh.moveChunk("feedback.usage", { "_id" : d.min._id }, "rs1");
});
sh.setBalancerState(true)
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