- ported to daemon_spec

- used as example of exn_handler to avoid sigpipe kill processes
  holding mutexes

diff --git a/helm/DEVEL/ocaml-http/examples/threads.ml b/helm/DEVEL/ocaml-http/examples/threads.ml
index a73f422d8199c11106d9687219105ab8f9035b37..01f6dae4c3ea30ed25f0389be13b00915263cc86 100644 (file)
--- a/helm/DEVEL/ocaml-http/examples/threads.ml
+++ b/helm/DEVEL/ocaml-http/examples/threads.ml
@@ -19,29 +19,45 @@
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *)
 
-let m = Mutex.create () in
-let i = ref 10 in
+open Http_types
+
+let m = Mutex.create ()
+let m_locked = ref true
+
+let critical f =
+  Mutex.lock m;
+    m_locked := true;
+    Lazy.force f;
+    m_locked := false;
+  Mutex.unlock m
+
+  (** ocaml's Thread.unlock suspend the invoking process if the mutex is already
+  * unlocked, therefore we unlock it only if we know that it's currently locked
+  *)
+let safe_unlock _ _ = if !m_locked then Mutex.unlock m
+
+let i = ref 10
 let dump_i outchan =
   Http_daemon.respond ~body:(Printf.sprintf "i = %d\n" !i) outchan
-in
+
 let callback req outchan =
   match req#path with
-  | "/incr" ->
-      Mutex.lock m;
-      incr i;
-      dump_i outchan;
-      Unix.sleep 5;
-      Mutex.unlock m
-  | "/decr" ->
-      Mutex.lock m;
-      decr i;
-      dump_i outchan;
-      Unix.sleep 5;
-      Mutex.unlock m
-  | "/get" ->
-      Mutex.lock m;
-      dump_i outchan;
-      Mutex.unlock m
+  | "/incr" -> critical (lazy (incr i; dump_i outchan; Unix.sleep 5))
+  | "/decr" -> critical (lazy (decr i; dump_i outchan; Unix.sleep 5))
+  | "/get"  -> critical (lazy (dump_i outchan))
   | bad_request -> Http_daemon.respond_error outchan
-in
-Http_daemon.start' ~port:9999 ~mode:`Thread callback
+
+let spec =
+  { Http_daemon.default_spec with
+      port = 9999;
+      mode = `Thread;
+      callback = callback;
+      exn_handler = Some safe_unlock;
+        (** ocaml-http's default exn_handler is Pervasives.ignore. This means
+        * that threads holding the "m" mutex above may die without unlocking it.
+        * Using safe_unlock as an exception handler we ensure that "m" mutex is
+        * unlocked in case of exceptions (e.g. SIGPIPE) *)
+  }
+
+let _ = Http_daemon.main spec
+