CA-160971: Improve patch_apply failure error reporting

Raise a proper Api_error if patch_apply fails
when patch backup files are created
And user tries to re-apply the patch

Signed-off-by: Sharad Yadav <[email protected]>

Author: sharady

ocaml/idl/api_errors.ml

@@ -335,6 +335,7 @@ let patch_precheck_failed_wrong_server_build = "PATCH_PRECHECK_FAILED_WRONG_SERV
 let patch_precheck_failed_vm_running = "PATCH_PRECHECK_FAILED_VM_RUNNING"
 let patch_precheck_tools_iso_mounted = "PATCH_PRECHECK_FAILED_ISO_MOUNTED"
 let patch_apply_failed = "PATCH_APPLY_FAILED"
+let patch_apply_failed_backup_files_exists = "PATCH_APPLY_FAILED_BACKUP_FILES_EXISTS"
 let cannot_find_oem_backup_partition = "CANNOT_FIND_OEM_BACKUP_PARTITION"
 let only_allowed_on_oem_edition = "ONLY_ALLOWED_ON_OEM_EDITION"
 let not_allowed_on_oem_edition = "NOT_ALLOWED_ON_OEM_EDITION"

ocaml/idl/datamodel.ml

@@ -1091,6 +1091,8 @@ let _ =
     ~doc:"This patch has already been applied" ();
   error Api_errors.patch_apply_failed [ "output" ]
     ~doc:"The patch apply failed.  Please see attached output." ();
+  error Api_errors.patch_apply_failed_backup_files_exists [ "output" ]
+    ~doc:"The patch apply failed" ();
   error Api_errors.patch_precheck_failed_unknown_error [ "patch"; "info" ]
     ~doc:"The patch precheck stage failed with an unknown error.  See attached info for more details." ();
   error Api_errors.patch_precheck_failed_prerequisite_missing [ "patch"; "prerequisite_patch_uuid_list" ]

ocaml/xapi/xapi_pool_patch.ml

@@ -645,8 +645,18 @@ let apply ~__context ~self ~host =
 	        output;
 
         | Failure(log, exn) ->
-	        debug "error from patch application: %s" log;
-	        raise (Api_errors.Server_error(Api_errors.patch_apply_failed, [log]))
+		debug "error from patch application: %s" log;
+           	let error_string = "Backup files already present - aborting." in
+           	if List.length (Xstringext.String.find_all error_string log) = 0 then
+               		raise (Api_errors.Server_error(Api_errors.patch_apply_failed, [log]))
+           	else begin
+               		let xml = Xml.parse_string log in
+               		match xml with
+               		| Element ("error", [("errorcode", "PATCH_PRECHECK_FAILED_UNKNOWN_ERROR")], [Element("info", _, [PCData info])]) ->
+                    		raise (Api_errors.Server_error(Api_errors.patch_apply_failed_backup_files_exists, [info]))
+               		| _ ->
+                   		raise (Bad_precheck_xml "Could not find element info")
+           	end
     end
 
 let pool_apply ~__context ~self =