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Type:
Bug
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Resolution: Done
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Priority:
Minor - P4
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None
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Affects Version/s: 2.4.9, 2.6.5
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Component/s: Sharding
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None
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ALL
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Sharding 2019-07-01
After removing one RS member in a shard, MongoS updates config.shards but keeps the stale shard string in the explain() output.
Create a new sharded collection with a single record:
mongos> sh.enableSharding("beep")
{ "ok" : 1 }
mongos> sh.shardCollection("beep.beeps",{_id:1})
{ "collectionsharded" : "beep.beeps", "ok" : 1 }
mongos> use beep
switched to db beep
mongos> db.beeps.insert({x:1})
WriteResult({ "nInserted" : 1 })
mongos> db.beeps.find()
{ "_id" : ObjectId("5463ac6986131a1d5750adcd"), "x" : 1 }
mongos> db.beeps.find({ "_id" : ObjectId("5463ac6986131a1d5750adcd")}).explain()
{
"clusteredType" : "ParallelSort",
"shards" : {
"db_0/AlexMMSADemo-0.mralex.9768.mongodbdns.com:27000,AlexMMSADemo-1.mralex.9768.mongodbdns.com:27000,AlexMMSADemo-2.mralex.9768.mongodbdns.com:27000" : [
{
"cursor" : "IDCursor",
"n" : 1,
"nscannedObjects" : 1,
"nscanned" : 1,
"indexOnly" : false,
"millis" : 0,
"indexBounds" : {
"_id" : [
[
ObjectId("5463ac6986131a1d5750adcd"),
ObjectId("5463ac6986131a1d5750adcd")
]
]
},
"server" : "AlexMMSADemo-0.mralex.9768:27000"
}
]
},
"cursor" : "IDCursor",
"n" : 1,
"nscanned" : 1,
"nscannedObjects" : 1,
"millisShardTotal" : 0,
"millisShardAvg" : 0,
"numQueries" : 1,
"numShards" : 1,
"indexBounds" : {
"_id" : [
[
ObjectId("5463ac6986131a1d5750adcd"),
ObjectId("5463ac6986131a1d5750adcd")
]
]
},
"millis" : 0
}
mongos> sh.status()
--- Sharding Status ---
sharding version: {
"_id" : 1,
"version" : 4,
"minCompatibleVersion" : 4,
"currentVersion" : 5,
"clusterId" : ObjectId("5463abcdd77c8abb282138a4")
}
shards:
{ "_id" : "db_0", "host" : "db_0/AlexMMSADemo-0.mralex.9768.mongodbdns.com:27000,AlexMMSADemo-1.mralex.9768.mongodbdns.com:27000,AlexMMSADemo-2.mralex.9768.mongodbdns.com:27000" }
{ "_id" : "db_1", "host" : "db_1/AlexMMSADemo-0.mralex.9768.mongodbdns.com:27001,AlexMMSADemo-0.mralex.9768.mongodbdns.com:27002,AlexMMSADemo-1.mralex.9768.mongodbdns.com:27001" }
databases:
{ "_id" : "admin", "partitioned" : false, "primary" : "config" }
{ "_id" : "beep", "partitioned" : true, "primary" : "db_0" }
beep.beeps
shard key: { "_id" : 1 }
chunks:
db_0 1
{ "_id" : { "$minKey" : 1 } } -->> { "_id" : { "$maxKey" : 1 } } on : db_0 Timestamp(1, 0)
Remove one replica set node and see that the shard description in the explain() output still has the old node in it:
mongos> sh.status()
--- Sharding Status ---
sharding version: {
"_id" : 1,
"version" : 4,
"minCompatibleVersion" : 4,
"currentVersion" : 5,
"clusterId" : ObjectId("5463abcdd77c8abb282138a4")
}
shards:
{ "_id" : "db_0", "host" : "db_0/AlexMMSADemo-0.mralex.9768.mongodbdns.com:27000,AlexMMSADemo-1.mralex.9768.mongodbdns.com:27000" }
{ "_id" : "db_1", "host" : "db_1/AlexMMSADemo-0.mralex.9768.mongodbdns.com:27001,AlexMMSADemo-0.mralex.9768.mongodbdns.com:27002,AlexMMSADemo-1.mralex.9768.mongodbdns.com:27001" }
databases:
{ "_id" : "admin", "partitioned" : false, "primary" : "config" }
{ "_id" : "beep", "partitioned" : true, "primary" : "db_0" }
beep.beeps
shard key: { "_id" : 1 }
chunks:
db_0 1
{ "_id" : { "$minKey" : 1 } } -->> { "_id" : { "$maxKey" : 1 } } on : db_0 Timestamp(1, 0)
mongos> db.beeps.find({ "_id" : ObjectId("5463ac6986131a1d5750adcd")}).explain()
{
"clusteredType" : "ParallelSort",
"shards" : {
"db_0/AlexMMSADemo-0.mralex.9768.mongodbdns.com:27000,AlexMMSADemo-1.mralex.9768.mongodbdns.com:27000,AlexMMSADemo-2.mralex.9768.mongodbdns.com:27000" : [
{
"cursor" : "IDCursor",
"n" : 1,
"nscannedObjects" : 1,
"nscanned" : 1,
"indexOnly" : false,
"millis" : 0,
"indexBounds" : {
"_id" : [
[
ObjectId("5463ac6986131a1d5750adcd"),
ObjectId("5463ac6986131a1d5750adcd")
]
]
},
"server" : "AlexMMSADemo-0.mralex.9768:27000"
}
]
},
"cursor" : "IDCursor",
"n" : 1,
"nscanned" : 1,
"nscannedObjects" : 1,
"millisShardTotal" : 0,
"millisShardAvg" : 0,
"numQueries" : 1,
"numShards" : 1,
"indexBounds" : {
"_id" : [
[
ObjectId("5463ac6986131a1d5750adcd"),
ObjectId("5463ac6986131a1d5750adcd")
]
]
},
"millis" : 0
}
Wait some time to be sure:
mongos> new Date()
ISODate("2014-11-12T18:57:44.499Z")
mongos> new Date()
ISODate("2014-11-12T18:59:23.038Z")
mongos> db.beeps.find({ "_id" : ObjectId("5463ac6986131a1d5750adcd")}).explain()
{
"clusteredType" : "ParallelSort",
"shards" : {
"db_0/AlexMMSADemo-0.mralex.9768.mongodbdns.com:27000,AlexMMSADemo-1.mralex.9768.mongodbdns.com:27000,AlexMMSADemo-2.mralex.9768.mongodbdns.com:27000" : [
{
"cursor" : "IDCursor",
"n" : 1,
"nscannedObjects" : 1,
"nscanned" : 1,
"indexOnly" : false,
"millis" : 0,
"indexBounds" : {
"_id" : [
[
ObjectId("5463ac6986131a1d5750adcd"),
ObjectId("5463ac6986131a1d5750adcd")
]
]
},
"server" : "AlexMMSADemo-0.mralex.9768:27000"
}
]
},
"cursor" : "IDCursor",
"n" : 1,
"nscanned" : 1,
"nscannedObjects" : 1,
"millisShardTotal" : 0,
"millisShardAvg" : 0,
"numQueries" : 1,
"numShards" : 1,
"indexBounds" : {
"_id" : [
[
ObjectId("5463ac6986131a1d5750adcd"),
ObjectId("5463ac6986131a1d5750adcd")
]
]
},
"millis" : 0
}
mongos>