I asked on StackOverflow (http://stackoverflow.com/questions/6118411/why-do-my-mongodb-logs-fill-up-with-getmore-local-oplog-rs) and people reported seeing the same thing, even on a totally new/fresh server.

This is repeated over and over again in my MongoDB logs on the primary replica. Note, also, that new Date(5610408224193773570) is always the same!

Wed May 25 00:35:58 [dur] lsn set 1552362
Wed May 25 00:36:02 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:36:06 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:36:11 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3884ms
Wed May 25 00:36:15 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:36:19 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:36:23 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:36:27 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:36:31 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:36:35 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:36:39 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:36:43 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:36:47 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:36:51 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:36:55 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:36:58 [dur] lsn set 1582372
Wed May 25 00:36:59 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:37:02 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:817 nreturned:1 3229ms
Wed May 25 00:37:06 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3685ms
Wed May 25 00:37:10 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:37:14 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:37:18 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:37:22 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:37:26 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:37:30 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:37:34 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:37:38 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:37:42 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:37:46 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:37:50 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:37:54 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:37:58 [conn14] getmore local.oplog.rs cid:265112601668423723 getMore: { ts:

{ $gte: new Date(5610408224193773570) }

} bytes:20 nreturned:0 3979ms
Wed May 25 00:37:58 [dur] lsn set 1612372