copydb fails via mongos

Set up a sharded cluster of two replica sets, and call copydb on mongos: var rsOpts = { oplogSize: 10 }; var st = new ShardingTest({shards : 1, mongos : 1, rs: rsOpts, verbose : 0});   var mongos = st.s; var test1 = mongos.getDB('test1'); var test2 = mongos.getDB('test2');   test1.getCollection('test').insert({foo: 'bar'}); jsTestLog('Test document on source db:'); printjson(test1.getCollection('test').findOne()); jsTestLog('copydb'); var result = mongos.getDB('admin').copyDatabase('test1', 'test2'); printjson(result); assert.eq(result.ok, 1.0); jsTestLog('Test document on destination db:'); printjson(test2.getCollection('test').findOne()); With mongod 2.4.9, the database is copied and copydb returns "ok": 1. With mongod 2.6.0-rc0 / hash 3779bf41, we get: { "ok" : 0, "errmsg" : "couldn't connect to server shard1/localhost:4002,localhost:4003 (shard1/localhost:4002,localhost), connection attempt failed", "$gleStats" : { "lastOpTime" : Timestamp(0, 0), "electionId" : ObjectId("530758b3c9aea15f7b4c58bb") } } The fault seems to be mongod's, since copydb works with old mongod and new mongos. copydb always works if the shards aren't replica sets.