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Type:
Task
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Resolution: Fixed
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Priority:
Major - P3
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Affects Version/s: None
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Component/s: Index Maintenance, Sharding
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Labels:
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Fully Compatible
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Sharding 2019-07-15
This only affects debug builds, since the assertion is a dassert. In a sharded cluster, I have an existing sharded collection sharded on {"shardKey": "hashed"}:
mongos> sh.shardCollection("test.sharded", {shardKey: "hashed"}) { "collectionsharded" : "test.sharded", "collectionUUID" : UUID("872244a4-4045-444c-b014-61170c3bc6da"), "ok" : 1, "operationTime" : Timestamp(1533326578, 10), "$clusterTime" : { "clusterTime" : Timestamp(1533326578, 10), "signature" : { "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="), "keyId" : NumberLong(0) } } }
This index creation trips the invariant failure:
mongos> db.sharded.createIndex({shardKey: "hashed", x: 1, y: 1}, {unique: true})
{
"raw" : {
"shardingtest-rs0/kimchi:20000" : {
"ok" : 0,
"errmsg" : "Connection was closed",
"code" : 6,
"codeName" : "HostUnreachable"
},
"shardingtest-rs1/kimchi:20001" : {
"ok" : 0,
"errmsg" : "Connection was closed",
"code" : 6,
"codeName" : "HostUnreachable"
}
},
"code" : 6,
"codeName" : "HostUnreachable",
"ok" : 0,
"errmsg" : "{ shardingtest-rs0/kimchi:20000: \"Connection was closed\", shardingtest-rs1/kimchi:20001: \"Connection was closed\" }",
"operationTime" : Timestamp(1533326580, 1),
"$clusterTime" : {
"clusterTime" : Timestamp(1533326580, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
}
}
The invariant failure in question is
d20001| 2018-08-03T16:03:00.733-0400 F - [conn21] Invariant failure !KeyPattern::isHashedKeyPattern(uniqueIndexPattern) src/mongo/s/shard_key_pattern.cpp 351
The failing assertion is here. It seems like we should be doing more validation beforehand before hitting the invariant, though.
shard_key_pattern.cpp
bool ShardKeyPattern::isUniqueIndexCompatible(const BSONObj& uniqueIndexPattern) const { dassert(!KeyPattern::isHashedKeyPattern(uniqueIndexPattern)); if (!uniqueIndexPattern.isEmpty() && uniqueIndexPattern.firstElementFieldName() == kIdField) { return true; } return _keyPattern.toBSON().isFieldNamePrefixOf(uniqueIndexPattern); }