Merge pull request #28 from gaborigloi/cleanup

Cleanup and documentation for CA-273309

.travis.yml

@@ -7,7 +7,6 @@ env:
     - OCAML_VERSION=4.04.2
     - DISTRO=debian-stable
     - PACKAGE=xapi-nbd
-    - PINS="nbd:git://github.com/xapi-project/nbd.git#bugfix-v2.x xen-api-client:git://github.com/xapi-project/xen-api-client#feature/CBT xen-api-client-lwt:git://github.com/xapi-project/xen-api-client#feature/CBT xen-api-client-async:git://github.com/xapi-project/xen-api-client#feature/CBT"
   matrix:
     - BASE_REMOTE=git://github.com/xapi-project/xs-opam
     - EXTRA_REMOTES=git://github.com/xapi-project/xs-opam

src/cleanup.ml

@@ -163,6 +163,14 @@ module Block = struct
 end
 
 module Runtime = struct
+  (* Exceptions raised from signal handlers are not caught by the Lwt.finalize
+     functions unfortunately, therefore just raising an exception from the
+     signal handlers is not enough: We need to use a global reference instead
+     to collect the things to be cleaned up, and add cleanup code to the signal
+     handlers. It is still necessary to raise an exception from the signal
+     handlers to stop the program.
+     See https://github.com/ocsigen/lwt/issues/451 for details. *)
+
   let cleanup_resources signal =
     let cleanup () =
       Lwt_log.warning_f "Caught signal %d, cleaning up" signal >>= fun () ->

src/main.ml

@@ -61,8 +61,6 @@ let handle_connection fd tls_role =
     let vdi_uuid = if path <> "" then String.sub path 1 (String.length path - 1) else path in
     Xen_api.VDI.get_by_uuid ~rpc ~session_id ~uuid:vdi_uuid
     >>= fun vdi_ref ->
-    Xen_api.VDI.get_record ~rpc ~session_id ~self:vdi_ref
-    >>= fun vdi_rec ->
     with_attached_vdi vdi_ref rpc session_id
       (fun filename ->
          Cleanup.Block.with_block filename (Nbd_lwt_unix.Server.serve t ~read_only:true (module Block))
@@ -219,7 +217,9 @@ let setup_logging () =
 let () =
   (* We keep track of the VBDs we've created but haven't yet cleaned up, and
      when we receive a SIGTERM or SIGINT signal, we clean up these leftover
-     VBDs first and then fail with an exception. *)
+     VBDs first and then fail with an exception.
+     This means that when systemd stops the service with SIGTERM, it will be
+     in the failed state, and a backtrace will show up in the logs. *)
   Cleanup.Runtime.register_signal_handler ();
   setup_logging ();
   match Term.eval cmd with