How many Host I need to instantiate?

[marimcmurtrie]

Hi, I just started leaning this. I am a bit confused about Host and connection pool. I need help for clarification.

I have Dynomite cluster in remote servers. See below. Details here: Netflix/dynomite#569

• data center:"dc1"

  • rack1:"dc1_rack1"
    • node1 - host:216.11.111.1, token:2147483647
    • node2 - host:216.11.111.1, token:4294967294

• data center:"dc2"

  • rack1:"dc2_rack1"
    • node1 - host:216.22.222.2, token: 1383429731
  • rack2:"dc2_rack2"
    • node1 - host: 216.22.222.2, token: 2147483647
    • node2 - host:216.22.222.2, token: 4294967294

I write client code with DynoJedis. I have questions about this client-side code. I generate own tokenMap:

[
  {
    "token": "2147483647",
    "hostname": "216.11.111.1",
    "zone": "dc1_rack1",
    "dc": "dc1"
  },
  {
    "token": "4294967294",
    "hostname": "216.11.111.1",
    "zone": "dc1_rack1",
    "dc": "dc1"
  },
  {
    "token": "1383429731",
    "hostname": "216.22.222.2",
    "zone": "dc2_rack1",
    "dc": "dc2"
  },
  {
    "token": "2147483647",
    "hostname": "216.22.222.2",
    "zone": "dc2_rack2",
    "dc": "dc2"
  },
  {
    "token": "4294967294",
    "hostname": "216.22.222.2",
    "zone": "dc2_rack2",
    "dc": "dc2"
  }
]

1. How many Host objects do I have to instantiate? I have 2 data centers and total of 5 nodes.
   (a) Do I need only 1 Host object for a given cluster?
   (b) 2 Host objects because I use 2 hosts for this cluster?
   (c) 5 Host objects since I have 5 nodes? That is probably not the case.

2. What the port should be when I instantiate the Host object? Should it be one of ports the nodes LISTEN to? I know default port is 8102.

3. Suppose only 1 Host is needed for HostSupplier, then doesn't it mean that all requests from a client goes to 1 node? I know if the first node does not have data, then it passes the request around, but if the initial requests all go to 1 node, then the node gets too busy, doesn't it? Or is the connection pool smart enough to handle that complexity?

Thanks for help!!

[marimcmurtrie]

I quickly read AWS and its terminology (region, availability_zone, etc). Is there an assumption that 1 host contains only 1 rack? That is why we instantiate Host with 1 rack with 1 port (this is LISTEN port of one of the nodes in the rack).? I set up my Dynomite so that 1 host contains multiple racks. If this is the case, then how many Host objects should I instantiate? Thanks.

[marimcmurtrie]

@ipapapa answered this in gitter so I close this issue.
How many Host I need -> "one, there is a connection pool underneath. Dyno opens connections to all nodes in the same datacenter. The connections are kept in the connection pool, so if a node goes down Dyno does not have pay the penalty to reopen a connection."