Send the plugboard cache only once per worker instead of once per job

src/calibre/gui2/save.py

@@ -88,7 +88,6 @@ class Saver(QObject):
         self.do_one_signal.connect(self.tick, type=Qt.QueuedConnection)
         self.do_one = self.do_one_collect
         self.ids_to_collect = iter(self.all_book_ids)
-        self.plugboards_cache = {}
         self.tdir = PersistentTemporaryDirectory('_save_to_disk')
         self.pool = None
 
@@ -113,7 +112,7 @@ class Saver(QObject):
             setattr(p, 'no_gc_%s' % id(self), None)
         if self.pool is not None:
             self.pool.shutdown()
-        self.jobs = self.pool = self.plugboards_cache = self.plugboards = self.template_functions = self.collected_data = self.all_book_ids = self.pd = self.db = None  # noqa
+        self.jobs = self.pool = self.plugboards = self.template_functions = self.collected_data = self.all_book_ids = self.pd = self.db = None  # noqa
 
     def book_id_data(self, book_id):
         ans = self._book_id_data.get(book_id)
@@ -153,8 +152,15 @@ class Saver(QObject):
         self.pd.value = 0
         if self.opts.update_metadata:
             all_fmts = {fmt for data in self.collected_data.itervalues() for fmt in data[2]}
-            self.plugboards_cache = {fmt:find_plugboard(plugboard_save_to_disk_value, fmt, self.plugboards) for fmt in all_fmts}
+            plugboards_cache = {fmt:find_plugboard(plugboard_save_to_disk_value, fmt, self.plugboards) for fmt in all_fmts}
             self.pool = Pool(name='SaveToDisk') if self.pool is None else self.pool
+            try:
+                self.pool.set_common_data(plugboards_cache)
+            except Failure as err:
+                error_dialog(self.pd, _('Critical failure'), _(
+                    'Could not save books to disk, click "Show details" for more information'),
+                    det_msg=unicode(err.failure_message) + '\n' + unicode(err.details), show=True)
+                self.pd.canceled = True
         self.do_one_signal.emit()
 
     def do_one_write(self):
@@ -260,11 +266,11 @@ class Saver(QObject):
         if self.opts.update_metadata:
             if d['fmts']:
                 try:
-                    self.pool(book_id, 'calibre.library.save_to_disk', 'update_serialized_metadata', d, self.plugboards_cache)
+                    self.pool(book_id, 'calibre.library.save_to_disk', 'update_serialized_metadata', d)
                 except Failure as err:
                     error_dialog(self.pd, _('Critical failure'), _(
                         'Could not save books to disk, click "Show details" for more information'),
-                        det_msg=unicode(err) + '\n' + unicode(err.details), show=True)
+                        det_msg=unicode(err.failure_message) + '\n' + unicode(err.details), show=True)
                     self.pd.canceled = True
             else:
                 self.pd.value += 1
@@ -298,7 +304,7 @@ class Saver(QObject):
         except Failure as err:
             error_dialog(self.pd, _('Critical failure'), _(
                 'Could not save books to disk, click "Show details" for more information'),
-                det_msg=unicode(err) + '\n' + unicode(err.details), show=True)
+                det_msg=unicode(err.failure_message) + '\n' + unicode(err.details), show=True)
             self.pd.canceled = True
         except RuntimeError:
             pass  # tasks not completed

src/calibre/library/save_to_disk.py

@@ -446,8 +446,9 @@ def read_serialized_metadata(data):
             cdata = f.read()
     return mi, cdata
 
-def update_serialized_metadata(book, plugboard_cache):
+def update_serialized_metadata(book, common_data=None):
     result = []
+    plugboard_cache = common_data
     from calibre.customize.ui import apply_null_metadata
     with apply_null_metadata:
 

src/calibre/utils/ipc/pool.py

@@ -26,6 +26,7 @@ class Failure(Exception):
         Exception.__init__(self, tf.message)
         self.details = tf.tb
         self.job_id = tf.job_id
+        self.failure_message = tf.message
 
 class Worker(object):
 
@@ -89,7 +90,8 @@ class Pool(Thread):
         needing to be transmitted every time. You must call this method before
         queueing any jobs, otherwise the behavior is undefined. You can call it
         after all jobs are done, then it will be used for the new round of
-        jobs. '''
+        jobs. Can raise the :class:`Failure` exception is data could not be
+        sent to workers.'''
         with self.lock:
             self.common_data = data
             for worker in self.available_workers:
@@ -99,7 +101,7 @@ class Pool(Thread):
                     import traceback
                     self.terminal_failure = TerminalFailure('Worker process crashed while sending common data', traceback.format_exc())
                     self.terminal_error()
-                    break
+                    raise Failure(self.terminal_failure)
 
     def start_worker(self):
         try: