Revert "Use all schedulable hosts"

This reverts commit a171bd2.

server/pkg/api/server_add_instance.go

@@ -231,7 +231,9 @@ func schedule(targets []targetHost, limitOverCommit uint64) (*targetHost, error)
 		return nil, ErrNoValidHost
 	}
 
-	return &schedulableTargets[rand.Intn(len(schedulableTargets))], nil
+	minTargets := getMinTargets(schedulableTargets)
+
+	return &minTargets[rand.Intn(len(minTargets))], nil
 }
 
 // parseAlias parse user input
@@ -270,3 +272,19 @@ func parseAlias(input string) (*api.InstanceSource, error) {
 		Alias: input,
 	}, nil
 }
+
+func getMinTargets(hosts []targetHost) []targetHost {
+	var minTargets []targetHost
+	// use lowest over-commit instance
+	// if there is more than one the lowest ones, it picks up from them randomly
+	minTargetOverCommit := hosts[0].percentOverCommit
+	for _, t := range hosts {
+		if minTargetOverCommit > t.percentOverCommit {
+			minTargetOverCommit = t.percentOverCommit
+			minTargets = []targetHost{t}
+		} else if minTargetOverCommit == t.percentOverCommit {
+			minTargets = append(minTargets, t)
+		}
+	}
+	return minTargets
+}

server/pkg/api/server_add_instance_test.go

@@ -0,0 +1,60 @@
+package api
+
+import (
+	"reflect"
+	"testing"
+)
+
+func Test_getMinTargets(t *testing.T) {
+	var (
+		hostA  = targetHost{percentOverCommit: 1}
+		hostA2 = targetHost{percentOverCommit: 1}
+		hostB  = targetHost{percentOverCommit: 2}
+		hostC  = targetHost{percentOverCommit: 3}
+	)
+
+	type args struct {
+		hosts []targetHost
+	}
+	tests := []struct {
+		name string
+		args args
+		want []targetHost
+	}{
+		{
+			name: "Single host",
+			args: args{
+				hosts: []targetHost{hostA},
+			},
+			want: []targetHost{hostA},
+		},
+		{
+			name: "Multiple host",
+			args: args{
+				hosts: []targetHost{hostA, hostB, hostC},
+			},
+			want: []targetHost{hostA},
+		},
+		{
+			name: "Multiple host (random order)",
+			args: args{
+				hosts: []targetHost{hostC, hostA, hostB},
+			},
+			want: []targetHost{hostA},
+		},
+		{
+			name: "Multiple host result",
+			args: args{
+				hosts: []targetHost{hostA, hostA2, hostB, hostC},
+			},
+			want: []targetHost{hostA, hostA2},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := getMinTargets(tt.args.hosts); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("getMinTargets() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}