mongodb 0.9.1

{
  "topology_description": {
    "type": "ReplicaSetNoPrimary",
    "servers": [
      {
        "address": "a:27017",
        "type": "Unknown"
      },
      {
        "address": "b:27017",
        "type": "Unknown"
      }
    ]
  },
  "read_preference": {
    "mode": "Nearest",
    "maxStalenessSeconds": 1
  },
  "error": true
}