Closedown

script/device/Image.py

@@ -71,6 +71,11 @@ class Image(DeviceBase, Readable):
     def get_int(self, filename = None):        
         if filename is None:
             filename = self.pixel.get_image_filename()
+
+        print "Waiting image file: " + filename 
+        wait_for_files([filename])
+        
+        
         threshold1 = self.pixel.threshold1
         threshold2 = self.pixel.threshold2
         threshold3 = self.pixel.threshold3

script/local.py

@@ -1,8 +1,10 @@
 ###################################################################################################
 #  Deployment specific global definitions - executed after startup.py
 ###################################################################################################
+import os
 import os.path
 
+
 ###################################################################################################
 #  Interlocks
 ###################################################################################################
@@ -263,9 +265,66 @@ def append_diag_datasets(parent = None):
             log("Error sampling " + str(get_diag_name(f)) + ": " + str(sys.exc_info()[1]))
 
 
-            
+
 ###################################################################################################
 #  Configuration 
 ###################################################################################################
 
-set_geometry(get_geometry(),True)          
+def is_locked(filepath):
+    """Checks if a file is locked by opening it in append mode.
+    If no exception thrown, then the file is not locked.
+    """
+    locked = None
+    file_object = None
+    if os.path.exists(filepath):
+        try:
+            print "Trying to open %s." % filepath
+            buffer_size = 8
+            # Opening file in append mode and read the first 8 characters.
+            file_object = open(filepath, 'a', buffer_size)
+            if file_object:
+                print "%s is not locked." % filepath
+                locked = False
+        except IOError, message:
+            print "File is locked (unable to open in append mode). %s." % \
+                  message
+            locked = True
+        finally:
+            if file_object:
+                file_object.close()
+                print "%s closed." % filepath
+    else:
+        print "%s not found." % filepath
+    return locked
+
+def wait_for_files(filepaths):
+    """Checks if the files are ready.
+
+    For a file to be ready it must exist and can be opened in append
+    mode.
+    """
+    wait_time = 5
+    for filepath in filepaths:
+        # If the file doesn't exist, wait wait_time seconds and try again
+        # until it's found.
+        while not os.path.exists(filepath):
+            print "%s hasn't arrived. Waiting %s seconds." % \
+                  (filepath, wait_time)
+            time.sleep(wait_time)
+        # If the file exists but locked, wait wait_time seconds and check
+        # again until it's no longer locked by another process.
+        while is_locked(filepath):
+            print "%s is currently in use. Waiting %s seconds." % \
+                  (filepath, wait_time)
+            time.sleep(wait_time)            
+
+
+
+###################################################################################################
+#  Configuration 
+###################################################################################################
+
+set_geometry(get_geometry(),True)      
+
+
+