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use test;
db.c.createIndex( { uid: 1} )
use config;
sh.enableSharding( "test" )
sh.shardCollection( "test.c" , { uid: 1 } )
sh.stopBalancer();
db.adminCommand({split : "test.c" , middle : {uid : 10} })
db.adminCommand({split : "test.c" , middle : {uid : 100} })
db.adminCommand({split : "test.c" , middle : {uid : 1000} })
db.settings.find();
// we want:
// { "_id" : "chunksize" , "value" : NumberLong(64) }
// { "_id" : "balancer" , "stopped" : true }
use test;
// doc ~270 B size, should get us a ~72 MB chunk with 251K docs - leave 8 B added by uid
var doc = {
"a" : ".23456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789.123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789.1234567890123456789012345678901234567890123456789012345678901"
};
for ( var ix=0; ix < 251000; ix++) {
doc.uid = 99;
// if ( ix % 2 == 0 ) { doc.uid = 100; } // should split ok into 99 and 100 -only chunks when chunkSize > maxChunkSize/2 (avoid SERVER-19919)
db.c.insert( doc );
if ( ix % 10000 == 0 ) { print(ix); }
}
print(ix);
db.c.stats();
sh.status( true );
Note the balancer is off and the Jumbo flags are absent, as initially expected:
mongos> sh.status( true )
--- Sharding Status ---
sharding version: {
"_id" : 1,
"minCompatibleVersion" : 5,
"currentVersion" : 6,
"clusterId" : ObjectId( "57fd594ff35daed3247bea8d" )
}
shards:
{ "_id" : "sh1" , "host" : "sh1/localhost:27018,localhost:27019" }
{ "_id" : "sh2" , "host" : "sh2/localhost:27020,localhost:27021" }
active mongoses:
{ "_id" : "Scotts-MacBook-Pro.local:27017" , "ping" : ISODate( "2016-10-11T21:41:26.026Z" ), "up" : NumberLong(822), "waiting" : true , "mongoVersion" : "3.2.8" }
balancer:
Currently enabled: no
Currently running: no
Failed balancer rounds in last 5 attempts: 0
Migration Results for the last 24 hours:
No recent migrations
databases:
{ "_id" : "test" , "primary" : "sh2" , "partitioned" : true }
test.c
shard key: { "uid" : 1 }
unique: false
balancing: true
chunks:
sh2 4
{ "uid" : { "$minKey" : 1 } } -->> { "uid" : 10 } on : sh2 Timestamp(1, 1)
{ "uid" : 10 } -->> { "uid" : 100 } on : sh2 Timestamp(1, 3)
{ "uid" : 100 } -->> { "uid" : 1000 } on : sh2 Timestamp(1, 5)
{ "uid" : 1000 } -->> { "uid" : { "$maxKey" : 1 } } on : sh2 Timestamp(1, 6)
Finally, start the balancer,
mongos> sh.startBalancer();
and note the server log entries and no-Jumbo flag result:
2016-10-11T14:42:27.572-0700 I SHARDING [Balancer] moving chunk ns: test.c moving ( ns: test.c, shard: sh2, lastmod: 2|1||57fd5ae3f35daed3247beaa7, min: { uid: 10.0 }, max: { uid: 100.0 }) sh2 -> sh1
2016-10-11T14:42:27.799-0700 I SHARDING [Balancer] moveChunk result: { chunkTooBig: true, estimatedChunkSize: 76304000, ok: 0.0, errmsg: "chunk too big to move" }
2016-10-11T14:42:27.801-0700 I SHARDING [Balancer] balancer move failed: { chunkTooBig: true, estimatedChunkSize: 76304000, ok: 0.0, errmsg: "chunk too big to move" } from: sh2 to: sh1 chunk: min: { uid: 10.0 } max: { uid: 100.0 }
2016-10-11T14:42:27.801-0700 I SHARDING [Balancer] performing a split because migrate failed for size reasons
2016-10-11T14:42:28.085-0700 I SHARDING [Balancer] split results: CannotSplit: chunk not full enough to trigger auto-split
2016-10-11T14:42:28.086-0700 I SHARDING [Balancer] marking chunk as jumbo: ns: test.c, shard: sh2, lastmod: 2|1||57fd5ae3f35daed3247beaa7, min: { uid: 10.0 }, max: { uid: 100.0 }
Inspecting the related source code for these messages ...
"performing a split because migrate failed for size reasons"
calls _splitOrMarkJumbo()
"CannotSplit: chunk not full enough to trigger auto-split"
"marking chunk as jumbo" calls chunk->markAsJumbo(txn)
Suggests the state of txn is deficient to permit setting the chunk's Jumbo flag. The resulting shard status is absent the Jumbo flag that should have been set:
mongos> sh.status(true)
--- Sharding Status ---
sharding version: {
"_id" : 1,
"minCompatibleVersion" : 5,
"currentVersion" : 6,
"clusterId" : ObjectId("57fd594ff35daed3247bea8d")
}
shards:
{ "_id" : "sh1", "host" : "sh1/localhost:27018,localhost:27019" }
{ "_id" : "sh2", "host" : "sh2/localhost:27020,localhost:27021" }
active mongoses:
{ "_id" : "Scotts-MacBook-Pro.local:27017", "ping" : ISODate("2016-10-11T21:55:54.530Z"), "up" : NumberLong(1690), "waiting" : true, "mongoVersion" : "3.2.8" }
balancer:
Currently enabled: yes
Currently running: no
Failed balancer rounds in last 5 attempts: 0
Migration Results for the last 24 hours:
2 : Success
1 : Failed with error 'chunk too big to move', from sh2 to sh1
databases:
{ "_id" : "test", "primary" : "sh2", "partitioned" : true }
test.c
shard key: { "uid" : 1 }
unique: false
balancing: true
chunks:
sh1 2
sh2 2
{ "uid" : { "$minKey" : 1 } } -->> { "uid" : 10 } on : sh2 Timestamp(7, 0)
{ "uid" : 10 } -->> { "uid" : 100 } on : sh2 Timestamp(6, 1)
{ "uid" : 100 } -->> { "uid" : 1000 } on : sh1 Timestamp(7, 1)
{ "uid" : 1000 } -->> { "uid" : { "$maxKey" : 1 } } on : sh1 Timestamp(4, 0)
Repeating with collection 'C' inserting TWO shard key values, uid = 99, 100 – splits normally:
use test;
db.C.createIndex( { uid: 1} )
use config;
sh.enableSharding( "test" )
sh.shardCollection( "test.C" , { uid: 1 } )
sh.stopBalancer();
db.adminCommand({split : "test.C" , middle : {uid : 10} })
db.adminCommand({split : "test.C" , middle : {uid : 100} })
db.adminCommand({split : "test.C" , middle : {uid : 1000} })
db.settings.find();
// we want:
// { "_id" : "chunksize" , "value" : NumberLong(64) }
// { "_id" : "balancer" , "stopped" : true }
use test;
// doc ~270 B size, should get us a ~72 MB chunk with 251K docs - leave 8 B added by uid
var doc = {
"a" : ".23456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789.123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789.1234567890123456789012345678901234567890123456789012345678901"
};
for ( var ix=0; ix < 251000; ix++) {
doc.uid = 99;
if ( ix % 2 == 0 ) { doc.uid = 100; } // should split ok into 99 and 100 -only chunks when chunkSize > maxChunkSize/2 (avoid SERVER-19919)
db.C.insert( doc );
if ( ix % 10000 == 0 ) { print(ix); }
}
print(ix);
db.C.stats();
sh.status( true );
mongos> sh.status( true );
Bug
Major - P3