func addMachineForUnit(st *state.State, unit *state.Unit, placement *instance.Placement, networks []string) (*state.Machine, error) {
unitCons, err := unit.Constraints()
if err != nil {
return nil, err
}
var containerType instance.ContainerType
var mid, placementDirective string
// Extract container type and parent from container placement directives.
if containerType, err = instance.ParseContainerType(placement.Scope); err == nil {
mid = placement.Directive
} else {
switch placement.Scope {
case st.EnvironUUID():
placementDirective = placement.Directive
case instance.MachineScope:
mid = placement.Directive
default:
return nil, errors.Errorf("invalid environment UUID %q", placement.Scope)
}
}
// Create any new machine marked as dirty so that
// nothing else will grab it before we assign the unit to it.
// If a container is to be used, create it.
if containerType != "" {
template := state.MachineTemplate{
Series: unit.Series(),
Jobs: []state.MachineJob{state.JobHostUnits},
Dirty: true,
Constraints: *unitCons,
RequestedNetworks: networks,
}
return st.AddMachineInsideMachine(template, mid, containerType)
}
// If a placement directive is to be used, do that here.
if placementDirective != "" {
template := state.MachineTemplate{
Series: unit.Series(),
Jobs: []state.MachineJob{state.JobHostUnits},
Dirty: true,
Constraints: *unitCons,
RequestedNetworks: networks,
Placement: placementDirective,
}
return st.AddOneMachine(template)
}
// Otherwise use an existing machine.
return st.Machine(mid)
}