SCTX-525: Reduce number of round-trips in the "PIF resynchronisation" logic

Pool:
* 5 hosts
* 300 VLANs (none in use)
xapi start time decreased from 129s to 100s.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>

diff --git a/ocaml/xapi/dbsync_slave.ml b/ocaml/xapi/dbsync_slave.ml
index 1e3ddaad660a9ae9e28cca8f2ca7900c3a812e50..ed0fa72705cf14fc15b9b639b5ac548a0982e8fc 100644 (file)
--- a/ocaml/xapi/dbsync_slave.ml
+++ b/ocaml/xapi/dbsync_slave.ml
@@ -421,39 +421,61 @@ let remove_all_leaked_vbds __context =
  * For example, this will prevent needless glitches in storage interfaces.
  *)
 let resynchronise_pif_params ~__context =
-  let localhost = Helpers.get_localhost () in
-  (* See which PIFs were brought up at start of day, according to the inventory file *)
-  let pifs_brought_up =
-    try
-      let bridges_already_up = Xapi_pif.read_bridges_from_inventory () in
-      debug "HA interfaces: [%s]" (String.concat "; " bridges_already_up);
-      (* Create a list pairing each PIF with the bridge for the network that it is on *)
-      let pifs_with_bridges = List.map (fun (pif,pifr) -> (pif, Db.Network.get_bridge ~__context ~self:pifr.API.pIF_network)) (Db.PIF.get_all_records ~__context) in
-      (* Retain the (pif, bridge) pairs where the bridge was listed in the inventory as an HA interface *)
-      List.filter (fun (_,bridge_name) -> List.mem bridge_name bridges_already_up) pifs_with_bridges
-    with
-      Xapi_inventory.Missing_inventory_key _ -> []
-    in
-  List.iter
-    (fun self ->
-       let is_management_pif = Xapi_pif.is_my_management_pif ~__context ~self in
-       let was_pif_brought_up_at_start_of_day = List.mem self (List.map fst pifs_brought_up) in
-       (* Mark important interfaces as attached *)
-       let mark_as_attached = is_management_pif || was_pif_brought_up_at_start_of_day || 
-                              (Mtc.is_pif_attached_to_mtc_vms_and_should_not_be_offline ~__context ~self) in
-       Db.PIF.set_currently_attached ~__context ~self ~value:mark_as_attached;
-       Db.PIF.set_management ~__context ~self ~value:is_management_pif;
-       debug "Marking PIF device %s as %s" (Db.PIF.get_device ~__context ~self) (if mark_as_attached then "attached" else "offline");
-       
-       (* sync MTU *)
-       try
-         let device = Db.PIF.get_device ~__context ~self in
-         let mtu = Int64.of_string (Netdev.get_mtu device) in
-         Db.PIF.set_MTU ~__context ~self ~value:mtu;
-       with _ ->
-         debug "could not update MTU field on PIF %s" (Db.PIF.get_uuid ~__context ~self)
-    )
-    (Db.Host.get_PIFs ~__context ~self:localhost)
+       let localhost = Helpers.get_localhost () in
+       (* 1. Acquire data. We minimise round-trips not bandwidth *)
+       let networks = Db.Network.get_all_records ~__context in
+       let expr = Db_filter_types.Eq(Db_filter_types.Field "host", Db_filter_types.Literal (Ref.string_of localhost)) in
+       let pifs = Db.PIF.get_records_where ~__context ~expr in
+
+       (* 2. Inspect current system configuration *)
+       let bridges_already_up = 
+               try Xapi_pif.read_bridges_from_inventory ()
+               with Xapi_inventory.Missing_inventory_key _ -> [] in
+       debug "dom0 interfaces: [%s]" (String.concat "; " bridges_already_up);
+       let management_bridge = 
+               try [ Xapi_inventory.lookup Xapi_inventory._management_interface ]
+               with Xapi_inventory.Missing_inventory_key _ -> [] in                    
+       debug "management interface: [%s]" (String.concat "; " management_bridge);
+
+       (* 3. Produce internal lookup tables *)
+       let network_to_bridge = List.map (fun (net, net_r) -> net, net_r.API.network_bridge) networks in
+
+       (* PIF -> bridge option: None means "dangling PIF" *)
+       let pifs_to_bridge =
+               let all_up_bridges = management_bridge @ bridges_already_up in
+               (* Create a list pairing each PIF with the bridge for the network 
+                  that it is on *)
+               List.map (fun (pif, pif_r) ->
+                       let net = pif_r.API.pIF_network in
+                       let bridge = if List.mem_assoc net network_to_bridge
+                       then Some (List.assoc net network_to_bridge) else None in
+                       pif, bridge) pifs in
+
+       (* 4. Perform the database resynchronisation *)
+       List.iter
+               (fun (pif, pif_r) ->
+                       let all_up_bridges = management_bridge @ bridges_already_up in
+                       let bridge = List.assoc pif pifs_to_bridge in
+                       let currently_attached = Opt.default false (Opt.map (fun x -> List.mem x all_up_bridges) bridge) in
+                       let management = Opt.default false (Opt.map (fun x -> List.mem x management_bridge) bridge) in
+                       if pif_r.API.pIF_currently_attached <> currently_attached then begin
+                               Db.PIF.set_currently_attached ~__context ~self:pif ~value:currently_attached;
+                               debug "PIF %s currently_attached <- %b" (Ref.string_of pif) currently_attached;
+                       end;
+                       if pif_r.API.pIF_management <> management then begin
+                               Db.PIF.set_management ~__context ~self:pif ~value:management;
+                               debug "PIF %s management <- %b" (Ref.string_of pif) management;
+                       end;
+                       (* sync MTU *)
+                       try
+                               let mtu = Int64.of_string (Netdev.get_mtu pif_r.API.pIF_device) in
+                               if pif_r.API.pIF_MTU <> mtu then begin
+                                       Db.PIF.set_MTU ~__context ~self:pif ~value:mtu;
+                                       debug "PIF %s MTU <- %Ld" (Ref.string_of pif) mtu;
+                               end;
+                       with _ ->
+                               debug "could not update MTU field on PIF %s" (Db.PIF.get_uuid ~__context ~self:pif)
+               ) pifs       
 
 (* Update the database to reflect current state. Called for both start of day and after
    an agent restart. *)