[
  {
    "comment": "Promote Master and Slave normally.",
    "stateModel": "MasterSlave",
    "liveInstances": [
      "node_1",
      "node_2",
      "node_3"
    ],
    "preferenceList": [
      "node_1",
      "node_2",
      "node_3"
    ],
    "currentStateMap": {
      "node_1": "OFFLINE",
      "node_2": "OFFLINE",
      "node_3": "OFFLINE"
    },
    "disabledInstancesForPartition": [],
    "expectedBestPossibleStateMap": {
      "node_1": "MASTER",
      "node_2": "SLAVE",
      "node_3": "SLAVE"
    }
  },
  {
    "comment": "Normal case, assignment stays the same.",
    "stateModel": "MasterSlave",
    "liveInstances": [
      "node_1",
      "node_2",
      "node_3"
    ],
    "preferenceList": [
      "node_1",
      "node_2",
      "node_3"
    ],
    "currentStateMap": {
      "node_1": "MASTER",
      "node_2": "SLAVE",
      "node_3": "SLAVE"
    },
    "disabledInstancesForPartition": [],
    "expectedBestPossibleStateMap": {
      "node_1": "MASTER",
      "node_2": "SLAVE",
      "node_3": "SLAVE"
    }
  },
  {
    "comment": "Drop instance not in preferenceList(empty), no matter it's disabled or in ERROR state.",
    "stateModel": "MasterSlave",
    "liveInstances": [
      "node_1",
      "node_2",
      "node_3"
    ],
    "preferenceList": [],
    "currentStateMap": {
      "node_1": "MASTER",
      "node_2": "ERROR",
      "node_3": "SLAVE"
    },
    "disabledInstancesForPartition": [
      "node_1"
    ],
    "expectedBestPossibleStateMap": {
      "node_1": "DROPPED",
      "node_2": "DROPPED",
      "node_3": "DROPPED"
    }
  },
  {
    "comment": "node_1: disabled and live, set initial-state. node_2: disabled and non-live, do nothing. node_3: disabled but in ERROR, do nothing. node_3: ",
    "stateModel": "MasterSlave",
    "liveInstances": [
      "node_1",
      "node_3"
    ],
    "preferenceList": [
      "node_1",
      "node_2",
      "node_3"
    ],
    "currentStateMap": {
      "node_1": "MASTER",
      "node_3": "ERROR"
    },
    "disabledInstancesForPartition": [
      "node_1",
      "node_2",
      "node_3"
    ],
    "expectedBestPossibleStateMap": {
      "node_1": "OFFLINE"
    }
  },
  {
    "comment": "node_1 back live before node_2 become Master. Promote node_1 to Slave, at the same time promote node_2 to Master (for high-availability)",
    "stateModel": "MasterSlave",
    "liveInstances": [
      "node_1",
      "node_2",
      "node_3"
    ],
    "preferenceList": [
      "node_1",
      "node_2",
      "node_3"
    ],
    "currentStateMap": {
      "node_1": "OFFLINE",
      "node_2": "SLAVE",
      "node_3": "SLAVE"
    },
    "disabledInstancesForPartition": [],
    "expectedBestPossibleStateMap": {
      "node_1": "SLAVE",
      "node_2": "MASTER",
      "node_3": "SLAVE"
    }
  },
  {
    "comment": "node_1 come back live (or still transiting to Slave) after node_2 already become Master, node_2 stay as Master while promoting node_1 to Slave first (high-availability during node_1 recovery)",
    "stateModel": "MasterSlave",
    "liveInstances": [
      "node_1",
      "node_2",
      "node_3"
    ],
    "preferenceList": [
      "node_1",
      "node_2",
      "node_3"
    ],
    "currentStateMap": {
      "node_1": "OFFLINE",
      "node_2": "MASTER",
      "node_3": "SLAVE"
    },
    "disabledInstancesForPartition": [],
    "expectedBestPossibleStateMap": {
      "node_1": "SLAVE",
      "node_2": "MASTER",
      "node_3": "SLAVE"
    }
  },
  {
    "comment": "After node_1 become Slave, switch Master and Slave.",
    "stateModel": "MasterSlave",
    "liveInstances": [
      "node_1",
      "node_2",
      "node_3"
    ],
    "preferenceList": [
      "node_1",
      "node_2",
      "node_3"
    ],
    "currentStateMap": {
      "node_1": "SLAVE",
      "node_2": "MASTER",
      "node_3": "SLAVE"
    },
    "disabledInstancesForPartition": [],
    "expectedBestPossibleStateMap": {
      "node_1": "MASTER",
      "node_2": "SLAVE",
      "node_3": "SLAVE"
    }
  },
  {
    "comment": "Rebalancer switched master to a new instance. Before the new instance ready, keep the master at the original node to avoid extra mastership handoff.",
    "stateModel": "MasterSlave",
    "liveInstances": [
      "node_1",
      "node_2",
      "node_3",
      "node_4"
    ],
    "preferenceList": [
      "node_4",
      "node_2",
      "node_1"
    ],
    "currentStateMap": {
      "node_1": "MASTER",
      "node_2": "SLAVE",
      "node_3": "SLAVE"
    },
    "disabledInstancesForPartition": [],
    "expectedBestPossibleStateMap": {
      "node_1": "MASTER",
      "node_2": "SLAVE",
      "node_3": "DROPPED",
      "node_4": "SLAVE"
    }
  }, {
    "comment": "For a multiple top state state model with complicated middle states, the rebalancer correctly handles the top states and assigns all instances with the expected state.",
    "stateModel": "OnlineOfflineWithBootstrap",
    "liveInstances": [
      "node_1",
      "node_2",
      "node_3"
    ],
    "preferenceList": [
      "node_3",
      "node_2",
      "node_1"
    ],
    "currentStateMap": {
      "node_1": "OFFLINE",
      "node_2": "ONLINE",
      "node_3": "ONLINE"
    },
    "disabledInstancesForPartition": [],
    "expectedBestPossibleStateMap": {
      "node_1": "ONLINE",
      "node_2": "ONLINE",
      "node_3": "ONLINE"
    }
  }
]