CA-366309: ignore HA when checking update readiness

In particular, the evacuation plan is computed in a different way when
HA is enabled. We want the update readiness to check things as if HA is
disabled, because before updates are applied, HA will be disabled anyway.

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>

ocaml/xapi/xapi_host.ml

@@ -257,7 +257,7 @@ let string_of_per_vm_plan p =
 
 (** Return a table mapping VMs to 'per_vm_plan' types indicating either a target
  Host or a reason why the VM cannot be migrated. *)
-let compute_evacuation_plan_no_wlb ~__context ~host =
+let compute_evacuation_plan_no_wlb ~__context ~host ?(ignore_ha = false) () =
  let all_hosts = Db.Host.get_all ~__context in
  let enabled_hosts =
  List.filter (fun self -> Db.Host.get_enabled ~__context ~self) all_hosts
@@ -308,7 +308,7 @@ let compute_evacuation_plan_no_wlb ~__context ~host =
  planner's PoV) to the result obtained following a host failure and VM restart. *)
  let pool = Helpers.get_pool ~__context in
  let protected_vms, unprotected_vms =
- if Db.Pool.get_ha_enabled ~__context ~self:pool then
+ if Db.Pool.get_ha_enabled ~__context ~self:pool && not ignore_ha then
  List.partition
  (fun (_, record) ->
  Helpers.vm_should_always_run record.API.vM_ha_always_run
@@ -393,7 +393,7 @@ let compute_evacuation_plan_no_wlb ~__context ~host =
 (* Old Miami style function with the strange error encoding *)
 let assert_can_evacuate ~__context ~host =
  (* call no_wlb function as we only care about errors, and wlb only provides recs for moveable vms *)
- let plans = compute_evacuation_plan_no_wlb ~__context ~host in
+ let plans = compute_evacuation_plan_no_wlb ~__context ~host () in
  let errors =
  Hashtbl.fold
  (fun _ plan acc ->
@@ -411,9 +411,10 @@ let assert_can_evacuate ~__context ~host =
  (Api_errors.cannot_evacuate_host, [String.concat "|" errors])
  )
 
-(* New Orlando style function which returns a Map *)
-let get_vms_which_prevent_evacuation ~__context ~self =
- let plans = compute_evacuation_plan_no_wlb ~__context ~host:self in
+let get_vms_which_prevent_evacuation_internal ~__context ~self ~ignore_ha =
+ let plans =
+ compute_evacuation_plan_no_wlb ~__context ~host:self ~ignore_ha ()
+ in
  Hashtbl.fold
  (fun vm plan acc ->
  match plan with
@@ -424,6 +425,10 @@ let get_vms_which_prevent_evacuation ~__context ~self =
  )
  plans []
 
+(* New Orlando style function which returns a Map *)
+let get_vms_which_prevent_evacuation ~__context ~self =
+ get_vms_which_prevent_evacuation_internal ~__context ~self ~ignore_ha:false
+
 let compute_evacuation_plan_wlb ~__context ~self =
  (* We treat xapi as primary when it comes to "hard" errors, i.e. those that aren't down to memory constraints. These are things like
  VM_REQUIRES_SR or VM_LACKS_FEATURE_SUSPEND.
@@ -438,7 +443,7 @@ let compute_evacuation_plan_wlb ~__context ~self =
  right thing to do because WLB doesn't know about all the HA corner cases (for example), but xapi does.
  If there are any VMs left over, record them as HOST_NOT_ENOUGH_FREE_MEMORY, because we assume that WLB thinks they don't fit.
  *)
- let error_vms = compute_evacuation_plan_no_wlb ~__context ~host:self in
+ let error_vms = compute_evacuation_plan_no_wlb ~__context ~host:self () in
  let vm_recoms =
  get_evacuation_recoms ~__context ~uuid:(Db.Host.get_uuid ~__context ~self)
  in
@@ -538,7 +543,7 @@ let compute_evacuation_plan ~__context ~host =
  debug
  "Using wlb recommendations for choosing a host has been disabled or wlb \
  is not available. Using original algorithm" ;
- compute_evacuation_plan_no_wlb ~__context ~host
+ compute_evacuation_plan_no_wlb ~__context ~host ()
  ) else
  try
  debug "Using WLB recommendations for host evacuation." ;
@@ -565,12 +570,12 @@ let compute_evacuation_plan ~__context ~host =
  )
  with _ -> ()
  ) ;
- compute_evacuation_plan_no_wlb ~__context ~host
+ compute_evacuation_plan_no_wlb ~__context ~host ()
  | _ ->
  debug
  "Encountered an unknown error when using wlb for choosing host. \
  Using original algorithm" ;
- compute_evacuation_plan_no_wlb ~__context ~host
+ compute_evacuation_plan_no_wlb ~__context ~host ()
 
 let evacuate ~__context ~host ~network =
  let task = Context.get_task_id __context in

ocaml/xapi/xapi_host.mli

@@ -54,6 +54,15 @@ val assert_can_evacuate : __context:Context.t -> host:API.ref_host -> unit
 val get_vms_which_prevent_evacuation :
  __context:Context.t -> self:API.ref_host -> (API.ref_VM * string list) list
 
+(* Similar to the (API) call `host.get_vms_which_prevent_evacuation`, but with an
+ additional `ignore_ha` argument. The makes the evacuation planner behave the
+ same no matter whether HA is enabled or not. *)
+val get_vms_which_prevent_evacuation_internal :
+ __context:Context.t
+ -> self:API.ref_host
+ -> ignore_ha:bool
+ -> (API.ref_VM * string list) list
+
 val evacuate :
  __context:Context.t -> host:API.ref_host -> network:API.ref_network -> unit
 

ocaml/xapi/xapi_pool.ml

@@ -3440,7 +3440,8 @@ let check_update_readiness ~__context ~self:_ ~requires_reboot =
  if not alive then
  [[Api_errors.host_offline; Ref.string_of host]]
  else if requires_reboot then
- Xapi_host.get_vms_which_prevent_evacuation ~__context ~self:host
+ Xapi_host.get_vms_which_prevent_evacuation_internal ~__context ~self:host
+ ~ignore_ha:true
  |> List.map (fun (_, error) -> error)
  else
  [[]]