mongos删除库表的一个bug

ISSUE SUMMARY

When dropping a database / collection in a sharded cluster, even if the drop is reported as successful it is possible the database / collection may still be present in some nodes in the cluster. At this time, we do not recommend that users drop a database or
collection and then attempt to reuse the namespace.

USER IMPACT

When the database/collection is not successfully dropped in a given node, the corresponding files continue to use disk space in that node. Attempting to reuse the namespace may lead to undefined behavior.

WORKAROUNDS

To work around this issue one can follow the steps below to drop a database/collection in a sharded environment:
Drop the database / collection using a mongos
Connect to each shard's primary and verify the namespace has been dropped. If it has not, please drop it. Dropping a database (e.g db.dropDatabase()) removes the data files on disk for the database being dropped.
Connect to a mongos, switch to the config database and remove any reference to the removed namespace from the collections chunks, locks, databases and collections:

When dropping a database:
use config
db.collections.remove( { _id: /^DATABASE\./ } )
db.databases.remove( { _id: "DATABASE" } )
db.chunks.remove( { ns: /^DATABASE\./ } )
db.locks.remove( { _id: /^DATABASE\./ } )

When dropping a collection:
use config
db.collections.remove( { _id: "DATABASE.COLLECTION" } )
db.chunks.remove( { ns: "DATABASE.COLLECTION" } )
db.locks.remove( { _id: "DATABASE.COLLECTION" } )

Connect to each mongos and run flushRouterConfig

PS：也遭遇了，真坑，原文链接https://jira.mongodb.org/browse/SERVER-17397