From: David Scott <dave.scott@eu.citrix.com>
Date: Mon, 12 Apr 2010 16:54:42 +0000 (+0100)
Subject: CA-40149: Add an explicit cache of the local hostname and make it posible to invalida... 
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=c123f14b51c1da682e2cd87fd6ab7c163c58b2d4;p=xcp%2Fxen-api-libs.git

CA-40149: Add an explicit cache of the local hostname and make it posible to invalidate the cache.

The hostname is included in every log line.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
---

diff --git a/log/debug.ml b/log/debug.ml
index bdd43e8..092b13e 100644
--- a/log/debug.ml
+++ b/log/debug.ml
@@ -22,11 +22,6 @@ let thread_tasks_m = Mutex.create ()
 let get_thread_id () =
   try Thread.id (Thread.self ()) with _ -> -1 
 
-(* Theses functions need to be defined later in the code. *)
-let get_hostname = 
-  let f () = "Debug.get_hostname not set" in
-  ref f
-
 let associate_thread_with_task task = 
   let id = get_thread_id () in
   if id <> -1
@@ -81,8 +76,18 @@ module type BRAND = sig
   val name: string
 end
 
+let hostname_cache = ref None
+let hostname_m = Mutex.create ()
+let get_hostname () =
+  match Mutex.execute hostname_m (fun () -> !hostname_cache) with
+  | Some h -> h
+  | None ->
+		let h = Unix.gethostname () in
+		Mutex.execute hostname_m (fun () -> hostname_cache := Some h);
+		h
+let invalidate_hostname_cache () = Mutex.execute hostname_m (fun () -> hostname_cache := None)
+
 module Debugger = functor(Brand: BRAND) -> struct
-  let hostname = Unix.gethostname ()
   let _ =
     Mutex.execute dkmutex (fun () -> 
       debug_keys := StringSet.add Brand.name !debug_keys)
@@ -102,7 +107,7 @@ module Debugger = functor(Brand: BRAND) -> struct
   let output (f:string -> ?extra:string -> ('a, unit, string, 'b) format4 -> 'a) fmt =
     let extra = 
       Printf.sprintf "%s|%s|%s|%s" 
-      hostname
+      (get_hostname ())
       (get_thread_name ()) 
       (get_task ())
       Brand.name
@@ -112,7 +117,7 @@ module Debugger = functor(Brand: BRAND) -> struct
 	let output_and_return ?raw (f:string -> ?raw:bool -> ?extra:string -> ('a, unit, string, 'b) format4 -> 'a) fmt =
     let extra =
       Printf.sprintf "%s|%s|%s|%s"
-      hostname
+      (get_hostname ())
       (get_thread_name ())
       (get_task ())
       Brand.name
diff --git a/log/debug.mli b/log/debug.mli
index 22e0013..2f2b53c 100644
--- a/log/debug.mli
+++ b/log/debug.mli
@@ -14,6 +14,9 @@
 
 (** Debug utilities *)
 
+(** Throw away the cached hostname. The next log line will re-query the hostname *)
+val invalidate_hostname_cache: unit -> unit
+
 (** {2 Associate a task to the current actions} *)
 
 (** Associate a task name to the current thread *)