tests: Test special watches with dying domains

Unit tests used to avoid calling Xenstored.main before, preferring to
call Process.process_packet to circumvent some hard-to-mock logic. As a
result, a few edge cases that can only be triggered from within the main
loop in xenstored.ml slipped through - hence the bug that required
45c16ec.

Now that xenstored.ml can handle being called in unit tests, we can
verify that the main loop handles shutdown and dead domains correctly,
sending the right number of correct special watch events when it needs
to.

Adds a hack to the mock domain_getinfo implementation, where all domids
> 2000 are always considered 'dying' and domains > 1000 are always
considered shutdown. Create a unit test that steps over the main loop in
xenstored.ml, verifying that the correct watch events are sent.

Signed-off-by: Andrii Sultanov <andriy.sultanov@vates.tech>

Author: last-genius

tests/plugin_interface_v1.ml

@@ -38,7 +38,13 @@ module Domain_getinfo_V1_impl = struct
   let interface_open () = 1
 
   let domain_getinfo _h domid =
-    {domid; dying= false; shutdown= false; shutdown_code= 1}
+    (* Special casing for test_introduce_release_watches_on_domain_death *)
+    if domid > 2000 then
+      {domid; dying= true; shutdown= false; shutdown_code= 1}
+    else if domid > 1000 then
+      {domid; dying= false; shutdown= true; shutdown_code= 1}
+    else
+      {domid; dying= false; shutdown= false; shutdown_code= 1}
 
   let domain_getinfolist _h =
     [|{domid= 1; dying= false; shutdown= false; shutdown_code= 1}|]

tests/unit_tests.ml

@@ -9,6 +9,19 @@ let initialize () =
   let cons = Connections.create () in
   (store, doms, cons)
 
+let initialize_main_loop () =
+  Domains.xenstored_port := "/tmp/port" ;
+  let fd =
+    Unix.openfile !Domains.xenstored_port [Unix.O_RDWR; Unix.O_CREAT] 0o600
+  in
+  let _ = Unix.write_substring fd "0" 0 1 in
+  Unix.close fd ;
+  Domains.xenstored_kva := "/tmp/kva" ;
+  let fd =
+    Unix.openfile !Domains.xenstored_kva [Unix.O_RDWR; Unix.O_CREAT] 0o600
+  in
+  Unix.close fd
+
 let create_dom0_conn cons doms =
   (* NOTE: We can't use Domains.create0 since that opens several files
      unavailable in the test env *)
@@ -434,11 +447,8 @@ let test_transaction_watches () =
   let actual = Xenbus.Xb.unsafe_pop_output dom0.xb in
   check_result actual (Transaction_end, ["OK"])
 
-(* Check that @introduceDomain and @releaseDomain watches appear on respective calls *)
-let test_introduce_release_watches () =
-  let store, doms, cons = initialize () in
-  let dom0 = create_dom0_conn cons doms in
-
+let register_spec_watches store cons doms dom0 =
+  (* Register both special watches *)
   run store cons doms
     [(dom0, none, (Watch, ["@introduceDomain"; "token"]), (Watch, ["OK"]))] ;
   assert_watches dom0 [("@introduceDomain", "token", None)] ;
@@ -450,7 +460,14 @@ let test_introduce_release_watches () =
   assert_watches dom0
     [("@releaseDomain", "token", None); ("@introduceDomain", "token", None)] ;
   (* One Watchevent is fired immediately after adding the watch unconditionally *)
-  check_for_watchevent dom0 "@releaseDomain" "token" ;
+  check_for_watchevent dom0 "@releaseDomain" "token"
+
+(* Check that @introduceDomain and @releaseDomain watches appear on respective calls *)
+let test_introduce_release_watches () =
+  let store, doms, cons = initialize () in
+  let dom0 = create_dom0_conn cons doms in
+
+  register_spec_watches store cons doms dom0 ;
 
   (* Watchevent is pushed to the queue first, then Introduce *)
   run store cons doms
@@ -470,6 +487,67 @@ let test_introduce_release_watches () =
   let actual = Xenbus.Xb.unsafe_pop_output dom0.xb in
   check_result actual (Release, ["OK"])
 
+(* Check that @introduceDomain and @releaseDomain watches appear on domains dying *)
+let test_introduce_release_watches_on_domain_death () =
+  (* Only the Xenstored.main loop checks for domains dying, so we need to
+     do special handling here unlike any other unit test *)
+  initialize_main_loop () ;
+  let one_loop_iteration, store, cons, doms = Xenstored.main () in
+  let dom0 = Hashtbl.find cons.domains 0 in
+
+  register_spec_watches store cons doms dom0 ;
+
+  (* Domains in [1000; 2000] are considered shutdown on the first query *)
+  let _ = create_domU_conn cons doms 1001 in
+  (* Check that a @releaseDomain watch event is sent when a domain shuts down *)
+  one_loop_iteration () ;
+  let actual = Xenbus.Xb.unsafe_pop_output dom0.xb in
+  check_result actual (Watchevent, ["@releaseDomain"; "token"]) ;
+  check_no_watchevents dom0 ;
+
+  (* Domains > 2000 are considered dead on the first query *)
+  let _ = create_domU_conn cons doms 2001 in
+  let _ = create_domU_conn cons doms 2002 in
+
+  (* Check that only a single @releaseDomain watch event is sent
+     when multiple domains die *)
+  one_loop_iteration () ;
+  let actual = Xenbus.Xb.unsafe_pop_output dom0.xb in
+  check_result actual (Watchevent, ["@releaseDomain"; "token"]) ;
+  check_no_watchevents dom0 ;
+
+  (* Register a releaseDomain with depth=1 *)
+  run store cons doms
+    [
+      ( dom0
+      , none
+      , (Watch, ["@releaseDomain"; "tokendepth"; "1"])
+      , (Watch, ["OK"])
+      )
+    ] ;
+  assert_watches dom0
+    [
+      ("@releaseDomain", "tokendepth", Some 1)
+    ; ("@releaseDomain", "token", None)
+    ; ("@introduceDomain", "token", None)
+    ] ;
+  (* One Watchevent is fired immediately after adding the watch unconditionally *)
+  check_for_watchevent dom0 "@releaseDomain" "tokendepth" ;
+
+  (* Verify that detailed watch events are sent when multiple domains die *)
+  let _ = create_domU_conn cons doms 2003 in
+  let _ = create_domU_conn cons doms 2004 in
+  one_loop_iteration () ;
+  let actual = Xenbus.Xb.unsafe_pop_output dom0.xb in
+  check_result actual (Watchevent, ["@releaseDomain/2004"; "tokendepth"]) ;
+  let actual = Xenbus.Xb.unsafe_pop_output dom0.xb in
+  check_result actual (Watchevent, ["@releaseDomain"; "token"]) ;
+  let actual = Xenbus.Xb.unsafe_pop_output dom0.xb in
+  check_result actual (Watchevent, ["@releaseDomain/2003"; "tokendepth"]) ;
+  let actual = Xenbus.Xb.unsafe_pop_output dom0.xb in
+  check_result actual (Watchevent, ["@releaseDomain/1001"; "tokendepth"]) ;
+  check_no_watchevents dom0
+
 (* Check that rm generates recursive watches *)
 let test_recursive_rm_watch () =
   let store, doms, cons = initialize () in
@@ -876,6 +954,10 @@ let () =
           , `Quick
           , test_introduce_release_watches
           )
+        ; ( "test_introduce_release_watches_on_domain_death"
+          , `Quick
+          , test_introduce_release_watches_on_domain_death
+          )
         ; ("test_recursive_rm_watch", `Quick, test_recursive_rm_watch)
         ; ("test_no_watch_on_error", `Quick, test_no_watch_on_error)
         ; ("test_watches_depth", `Quick, test_watches_depth)