ceph/doc/rados/configuration/mon-lookup-dns.rst

   1 ===============================
   2 Looking op Monitors through DNS
   3 ===============================
   4
   5 Since version 11.0.0 RADOS supports looking up Monitors through DNS.
   6
   7 This way daemons and clients do not require a *mon host* configuration directive in their ceph.conf configuration file.
   8
   9 Using DNS SRV TCP records clients are able to look up the monitors.
  10
  11 This allows for less configuration on clients and monitors. Using a DNS update clients and daemons can be made aware of changes in the monitor topology.
  12
  13 By default clients and daemons will look for the TCP service called *ceph-mon* which is configured by the *mon_dns_srv_name* configuration directive.
  14
  15
  16 ``mon dns srv name``
  17
  18 :Description: the service name used querying the DNS for the monitor hosts/addresses
  19 :Type: String
  20 :Default: ``ceph-mon``
  21
  22 Example
  23 -------
  24 When the DNS search domain is set to *example.com* a DNS zone file might contain the following elements.
  25
  26 First, create records for the Monitors, either IPv4 (A) or IPv6 (AAAA).
  27
  28 ::
  29
  30     mon1.example.com. AAAA 2001:db8::100
  31     mon2.example.com. AAAA 2001:db8::200
  32     mon3.example.com. AAAA 2001:db8::300
  33
  34 ::
  35
  36     mon1.example.com. A 192.168.0.1
  37     mon2.example.com. A 192.168.0.2
  38     mon3.example.com. A 192.168.0.3
  39
  40
  41 With those records now existing we can create the SRV TCP records with the name *ceph-mon* pointing to the three Monitors.
  42
  43 ::
  44
  45     _ceph-mon._tcp.example.com. 60 IN SRV 10 60 6789 mon1.example.com.
  46     _ceph-mon._tcp.example.com. 60 IN SRV 10 60 6789 mon2.example.com.
  47     _ceph-mon._tcp.example.com. 60 IN SRV 10 60 6789 mon3.example.com.
  48
  49 In this case the Monitors are running on port *6789*.
  50
  51 The current implementation in clients and daemons does *not* honor nor respect the weight or priority set in SRV records.
  52
  53 All records returned will be treated equally in a Round Robin fashion.