Major - P3 Related to SERVER-4232
If the collection does not live on the primary shard, mongodump won't dump the collection.
mongos> db.system.namespaces.find()
{ "name" : "test.system.indexes" }
{ "name" : "test.system.profile", "options" : { "capped" : true, "size" : 1048576 } }
mongos>
bye
$ mongodump --port 27020 -d test -c foo
connected to: 127.0.0.1:27020
Thu Nov 7 10:18:10.875 DATABASE: test to dump/test
$ ls -la dump/test/
total 0
drwxr-xr-x 2 joannac staff 68 7 Nov 10:17 .
drwxr-xr-x 3 joannac staff 102 7 Nov 10:17 ..
$ mongodump --port 27020 -d test
connected to: 127.0.0.1:27020
Thu Nov 7 10:32:52.016 DATABASE: test to dump/test
Thu Nov 7 10:32:52.017 test.system.indexes to dump/test/system.indexes.bson
Thu Nov 7 10:32:52.017 0 objects
Thu Nov 7 10:32:52.017 test.system.profile to dump/test/system.profile.bson
Thu Nov 7 10:32:52.027 1232 objects
Thu Nov 7 10:32:52.029 Metadata for test.system.profile to dump/test/system.profile.metadata.json
mongoexport of the collection works:
$ mongoexport --port 27020 -d test -c foo
connected to: 127.0.0.1:27020
{ "_id" : { "$oid" : "5279b9e2972221f9a6cf650b" }, "a" : 1 }
exported 1 records
but mongoexport of the system.indexes doesn't
$ mongoexport --port 27020 -d test -c system.indexes connected to: 127.0.0.1:27020 exported 0 records
This is now more than just a cosmetic problem (SERVER-4232 was just about show collections not showing the collection)