CA-61929: Don't return from DR_task.create until SR is ready.

When creating a DR_task, don't return until the asynchronous actions dealing with metadata VDIs have completed. This means that VDI.metadata_latest will be up to date for foreign database VDIs when DR_task.create returns.
johnelse · Aug 9, 2011 · 69ad9d1 · 69ad9d1
1 parent 763d1f8
commit 69ad9d1
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Showing 3 changed files with 50 additions and 6 deletions.
diff --git a/ocaml/xapi/message_forwarding.ml b/ocaml/xapi/message_forwarding.ml
@@ -3325,11 +3325,14 @@ end
 	    the internal scan function directly. 
       *)
 			Server_helpers.exec_with_new_task "PBD.plug initial SR scan" (fun __scan_context ->
-				let handle_metadata_vdis () =
+				(* Only handle metadata VDIs when attaching shared storage to the master. *)
-					(* Only handle metadata VDIs when attaching shared storage to the master. *)
+				let should_handle_metadata_vdis =
 					let pbd_host = Db.PBD.get_host ~__context:__scan_context ~self in
 					let master = Db.Pool.get_master ~__context:__scan_context ~self:(Helpers.get_pool ~__context:__scan_context) in
-					if (pbd_host = master) && (Db.SR.get_shared ~__context:__scan_context ~self:sr) then begin
+					(pbd_host = master) && (Db.SR.get_shared ~__context:__scan_context ~self:sr)
+				in
+				let handle_metadata_vdis () =
+					if should_handle_metadata_vdis then begin
 						debug "Shared SR %s is being plugged to master - handling metadata VDIs." (sr_uuid ~__context sr);
 						let metadata_vdis = List.filter
 							(fun vdi -> Db.VDI.get_type ~__context:__scan_context ~self:vdi = `metadata)
@@ -3354,10 +3357,13 @@ end
 							with e ->
 								debug "Could not re-enable database replication to VDI %s - caught %s"
 									vdi_uuid (Printexc.to_string e)
-						end
+						end;
+						Xapi_dr.signal_sr_is_ready ~__context:__scan_context ~sr
 					end else
 						debug "SR %s is not shared or is being plugged to a slave - not handling metadata VDIs at this point." (sr_uuid ~__context sr)
 				in
+				if should_handle_metadata_vdis then
+					Xapi_dr.signal_sr_is_processing ~__context:__scan_context ~sr;
 				Xapi_sr.scan_one ~__context:__scan_context ~callback:handle_metadata_vdis sr)
 
     let unplug ~__context ~self =

diff --git a/ocaml/xapi/xapi_dr.ml b/ocaml/xapi/xapi_dr.ml
@@ -5,6 +5,8 @@ open Threadext
 module D = Debug.Debugger(struct let name="xapi" end)
 open D
 
+(* -------------------------- VDI caching ----------------------------------- *)
+
 (* Keep track of foreign metadata VDIs and their database generations and pool UUIDs. *)
 (* The generation count is used to keep track of metadata_latest of all foreign database VDIs. *)
 (* The pool uuid is cached so that "xe pool-param-get param-name=metadata-of-pool" can be called without opening the database. *)
@@ -113,6 +115,42 @@ let read_vdi_cache_record ~vdi =
 			else
 				None)
 
+(* ------------ Providing signalling that an SR is ready for DR ------------- *)
+
+let processing_srs : API.ref_SR list ref = ref []
+let processing_srs_m = Mutex.create ()
+let processing_srs_c = Condition.create ()
+
+let signal_sr_is_processing ~__context ~sr =
+	debug "Recording that processing of SR %s has started." (Db.SR.get_uuid ~__context ~self:sr);
+	Mutex.execute processing_srs_m
+		(fun () ->
+			let srs = !processing_srs in
+			if not(List.mem sr srs) then
+				processing_srs := sr::srs)
+
+let signal_sr_is_ready ~__context ~sr =
+	debug "Recording that processing of SR %s has finished." (Db.SR.get_uuid ~__context ~self:sr);
+	Mutex.execute processing_srs_m
+		(fun () ->
+			let srs = !processing_srs in
+			if List.mem sr srs then begin
+				processing_srs := (List.filter (fun x -> x <> sr) srs);
+				Condition.broadcast processing_srs_c
+			end)
+
+let wait_until_sr_is_ready ~__context ~sr =
+	let sr_uuid = Db.SR.get_uuid ~__context ~self:sr in
+	Mutex.execute processing_srs_m
+		(fun () ->
+			debug "Waiting for SR %s to be processed." sr_uuid;
+			while List.mem sr !processing_srs do
+				Condition.wait processing_srs_c processing_srs_m
+			done;
+			debug "Finished waiting for SR %s to be processed." sr_uuid)
+
+(* --------------------------------- VM recovery ---------------------------- *)
+
 (* This function uses the VM export functionality to *)
 (* create the objects required to reimport a list of VMs *)
 let create_import_objects ~__context ~vms =

diff --git a/ocaml/xapi/xapi_dr_task.ml b/ocaml/xapi/xapi_dr_task.ml
@@ -78,8 +78,8 @@ let try_create_sr_from_record ~__context ~_type ~device_config ~dr_task ~sr_reco
 					debug "Attaching SR %s to host %s" sr_record.uuid (Db.Host.get_name_label ~__context ~self:host);
 					let pbd = Client.PBD.create ~rpc ~session_id ~host ~sR:sr ~device_config ~other_config:[] in
 					Client.PBD.plug ~rpc ~session_id ~self:pbd) hosts;
-				(* Ensure the VDI records are in the database. *)
+				(* Wait until the asynchronous scan is complete and metadata_latest has been updated for all metadata VDIs. *)
-				Client.SR.scan ~rpc ~session_id ~sr;
+				Xapi_dr.wait_until_sr_is_ready ~__context ~sr;
 				Db.SR.set_introduced_by ~__context ~self:sr ~value:dr_task
 			with e ->
 				(* Clean up if anything goes wrong. *)