Changeset 2883 for pykota/trunk

Timestamp:

05/11/06 16:08:45 (19 years ago)

Author:

jerome

Message:

Added locking to prevent two or more cupspykota processes to handle different
jobs for the same print queue at the very same time.

Location:

pykota/trunk

Files:

• bin/cupspykota (modified) (5 diffs)
• NEWS (modified) (1 diff)

pykota/trunk/bin/cupspykota

@@ -27 +27 @@
 import sys
 import os
+import fcntl
 import time
 import errno
@@ -113 +114 @@
         self.logdebug("SIGINT enabled.")
         
+    def waitForLock(self) :    
+        """Waits until we can acquire the lock file."""
+        self.logdebug("Waiting for lock...")
+        stillrunning = True
+        while 1 :
+            self.lockfile = open(self.lockfilename, "a+")
+            fcntl.lockf(self.lockfile, fcntl.LOCK_EX) # Will wait until lock available
+            self.lockfile.seek(0, 0)      
+            try : 
+                oldpid = int(self.lockfile.read().strip())
+            except :    
+                stillrunning = False
+            else :    
+                try :
+                    os.kill(oldpid, 0)
+                except OSError :    
+                    stillrunning = False
+            if not stillrunning :        
+                self.lockfile.seek(0, 0)
+                self.lockfile.write("%i" % self.pid)
+                self.lockfile.flush()
+                break
+            else :    
+                time.sleep(0.1)
+        self.logdebug("Lock acquired.")
+                    
     def discoverOtherBackends(self) :    
         """Discovers the other CUPS backends.
@@ -257 +284 @@
         (jbtype, self.JobBillingCode) = jbing
         
+        self.lockfilename = os.path.join(self.Directory, "%s-%s..LCK" % (self.myname, self.PrinterName))
+        
         self.logdebug("Backend : %s" % self.RealBackend)
         self.logdebug("DeviceURI : %s" % self.DeviceURI)
@@ -404 +433 @@
             self.logdebug("Work file %s will be kept." % self.DataFile)
         PyKotaTool.clean(self)    
+        self.logdebug("Removing lock...")
+        try :
+            fcntl.flock(self.lockfile, fcntl.LOCK_UN)
+            self.lockfile.close()
+            # NB : we don't remove the lock file, since it might already be opened by another process.
+        except :    
+            pass
+        else :    
+            self.logdebug("Lock removed.")
         self.logdebug("Clean.")
             
@@ -1251 +1289 @@
             wrapper.deferredInit()
             wrapper.initBackendParameters()
+            wrapper.waitForLock()
             wrapper.saveDatasAndCheckSum()
             wrapper.preaccounter = openAccounter(wrapper, ispreaccounter=1)

pykota/trunk/NEWS

@@ -24 +24 @@
     - 1.25alpha3 (2006-05-11) :
     
+        - Added a lock to ensure that a single cupspykota backend
+          is processing datas for a particular print queue at any
+          given time.
+          
         - Now exports more environment variables for the subprocesses.