[rucksack-cvs] CVS rucksack

[alemmens]

Update of /project/rucksack/cvsroot/rucksack
In directory clnet:/tmp/cvs-serv2990

Modified Files:
	cache.lisp transactions.lisp 
Log Message:
Ensure unique transaction IDs (from Edi Weitz).


--- /project/rucksack/cvsroot/rucksack/cache.lisp	2006/08/03 10:59:52	1.6
+++ /project/rucksack/cvsroot/rucksack/cache.lisp	2006/08/03 18:37:50	1.7
@@ -1,4 +1,4 @@
-;; $Id: cache.lisp,v 1.6 2006/08/03 10:59:52 alemmens Exp $
+;; $Id: cache.lisp,v 1.7 2006/08/03 18:37:50 alemmens Exp $
 
 (in-package :rucksack)
 
@@ -62,6 +62,11 @@
 cache."))
 
 
+(defgeneric make-transaction-id (cache)
+  (:documentation "Returns a new transaction ID.  The result is an
+integer greater than all previous IDs."))
+
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;; The cache
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -87,9 +92,10 @@
           :documentation "A queue of the ids of all non-dirty objects
 that are currently in the cache memory.  Whenever an object is
 retrieved (i.e. read), it's added to the queue.")
-   (highest-transaction-id :initarg :highest-transaction-id
-                           :initform 0
-                           :accessor highest-transaction-id)
+   (last-timestamp :initform (get-universal-time)
+                   :accessor last-timestamp)
+   (transaction-id-helper :initform -1
+                          :accessor transaction-id-helper)
    (transactions :initform (make-hash-table)
                  :reader transactions
                  :documentation "A mapping from transaction ids to
@@ -115,6 +121,18 @@
             (pathname (heap-stream (heap cache)))
             (cache-count cache))))
 
+ 
+(defmethod make-transaction-id ((cache standard-cache))
+  ;; This would allow for up to 100 transactions per millisecond
+  ;; The result is a bignum but it at least fits in 8 octets and
+  ;; can thus be serialized with SERIALIZE-BYTE-64.
+  (let ((timestamp (get-universal-time)))
+    (when (> timestamp (last-timestamp cache))
+      (setf (last-timestamp cache) timestamp
+            (transaction-id-helper cache) -1))
+    (+ (* timestamp 100000)
+       (mod (incf (transaction-id-helper cache)) 1000000))))
+
 ;;
 ;; Open/close/initialize
 ;;
--- /project/rucksack/cvsroot/rucksack/transactions.lisp	2006/08/03 11:52:46	1.5
+++ /project/rucksack/cvsroot/rucksack/transactions.lisp	2006/08/03 18:37:50	1.6
@@ -1,4 +1,4 @@
-;; $Id: transactions.lisp,v 1.5 2006/08/03 11:52:46 alemmens Exp $
+;; $Id: transactions.lisp,v 1.6 2006/08/03 18:37:50 alemmens Exp $
 
 (in-package :rucksack)
 
@@ -133,7 +133,7 @@
                                 (rucksack standard-rucksack)
                                 &key &allow-other-keys)
   ;; Create new transaction.
-  (let* ((id (incf (highest-transaction-id cache)))
+  (let* ((id (make-transaction-id cache))
          (transaction (make-instance 'standard-transaction :id id)))
     ;; Add to open transactions.
     (open-transaction cache transaction)