Uploaded image for project: 'Core Server'
  1. Core Server
  2. SERVER-16110

MongoS doesn't update the shard description in the explain() output

    XMLWordPrintable

    Details

    • Type: Bug
    • Status: Closed
    • Priority: Minor - P4
    • Resolution: Gone away
    • Affects Version/s: 2.4.9, 2.6.5
    • Fix Version/s: None
    • Component/s: Sharding
    • Labels:
      None
    • Operating System:
      ALL
    • Sprint:
      Sharding 2019-07-01

      Description

      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>

        Attachments

          Activity

            People

            Assignee:
            kaloian.manassiev Kaloian Manassiev
            Reporter:
            alex.komyagin Alexander Komyagin
            Participants:
            Votes:
            0 Vote for this issue
            Watchers:
            5 Start watching this issue

              Dates

              Created:
              Updated:
              Resolved: