zones: introduce Zone.GetCephMonitors()

returning the local ceph monitors and setting one
if there is none. non-gateway nodes are preferred
when setting a monitor automatically

Signed-off-by: Alejandro Mery <amery@jpi.io>

pkg/zones/ceph.go

@@ -2,6 +2,7 @@ package zones
 
 import (
 	"bytes"
+	"sort"
 
 	"darvaza.org/core"
 	"github.com/gofrs/uuid/v5"
@@ -28,3 +29,47 @@ func (m *Zones) GetCephConfig() (*ceph.Config, error) {
 	r := bytes.NewReader(data)
 	return ceph.NewConfigFromReader(r)
 }
+
+// GetCephMonitors returns the set of Ceph monitors on
+// the zone
+func (z *Zone) GetCephMonitors() Machines {
+	var mons Machines
+	var first, second *Machine
+
+	z.ForEachMachine(func(p *Machine) bool {
+		switch {
+		case p.CephMonitor:
+			// it is a monitor
+			mons = append(mons, p)
+		case len(mons) > 0:
+			// zone has a monitor
+		case first == nil && !p.IsGateway():
+			// first option for monitor
+			first = p
+		case second == nil:
+			// second option for monitor
+			second = p
+		}
+
+		return false
+	})
+
+	switch {
+	case len(mons) > 0:
+		// ready
+	case first != nil:
+		// make first option our monitor
+		first.CephMonitor = true
+		mons = append(mons, first)
+	case second != nil:
+		// make second option our monitor
+		second.CephMonitor = true
+		mons = append(mons, second)
+	default:
+		// zone without machines??
+		panic("unreachable")
+	}
+
+	sort.Sort(mons)
+	return mons
+}