Queue FTS jobs in a separate thread

This allows turning FTS on/off to not block the UI

src/calibre/db/cache.py

@@ -19,6 +19,7 @@ from functools import partial, wraps
 from io import DEFAULT_BUFFER_SIZE, BytesIO
 from threading import Lock
 from time import time
+from queue import Queue
 
 from calibre import as_unicode, isbytestring
 from calibre.constants import iswindows, preferred_encoding
@@ -139,6 +140,7 @@ class Cache:
     EventType = EventType
 
     def __init__(self, backend):
+        self.shutting_down = False
         self.backend = backend
         self.event_dispatcher = EventDispatcher()
         self.fields = {}
@@ -426,35 +428,48 @@ class Cache:
 
     # FTS API {{{
     def initialize_fts(self):
+        self.fts_queue_thread = None
+        self.fts_job_queue = Queue()
         self.backend.initialize_fts(weakref.ref(self))
         self.queue_next_fts_job()
 
-    def enable_fts(self, enabled=True, start_pool=True):
-        fts = self.backend.enable_fts(weakref.ref(self) if enabled else None)
-        if start_pool:  # used in the tests
-            self.queue_next_fts_job()
-        return fts
+    @read_api
+    def is_fts_enabled(self):
+        return self.backend.fts_enabled
 
     @write_api
-    def queue_next_fts_job(self):
+    def enable_fts(self, enabled=True, start_pool=True):
+        fts = self.backend.enable_fts(weakref.ref(self) if enabled else None)
+        if fts and start_pool:  # used in the tests
+            from threading import Thread
+            self.fts_queue_thread = Thread(name='FTSQueue', target=self.dispatch_fts_jobs, args=(self.fts_job_queue,), daemon=True)
+            self.fts_queue_thread.start()
+            fts.pool.initialize()
+            fts.pool.initialized.wait()
+            self.queue_next_fts_job()
+        if not fts and self.fts_queue_thread:
+            self.fts_job_queue.put(None)
+            self.fts_queue_thread = None
+            self.fts_job_queue = Queue()
+        return fts
+
+    def dispatch_fts_jobs(self, queue):
         from .fts.text import is_fmt_ok
-        if not self.backend.fts_enabled:
-            return
-        while True:
-            book_id, fmt = self.backend.get_next_fts_job()
-            if book_id is None:
-                return
-            path = self.format_abspath(book_id, fmt)
+
+        def do_one():
+            with self.read_lock:
+                if not self.backend.fts_enabled:
+                    return False
+                book_id, fmt = self.backend.get_next_fts_job()
+                if book_id is None:
+                    return False
+                path = self._format_abspath(book_id, fmt)
             if not path or not is_fmt_ok(fmt):
-                self.backend.remove_dirty_fts(book_id, fmt)
-                continue
-            try:
-                src = open(path, 'rb')
-            except OSError:
-                self.backend.remove_dirty_fts(book_id, fmt)
-                traceback.print_exc()
-                continue
-            with PersistentTemporaryFile(suffix=f'.{fmt.lower()}') as pt, src:
+                with self.write_lock:
+                    self.backend.remove_dirty_fts(book_id, fmt)
+                return True
+
+            with self.read_lock, open(path, 'rb') as src, PersistentTemporaryFile(suffix=f'.{fmt.lower()}') as pt:
                 sz = 0
                 h = hashlib.sha1()
                 while True:
@@ -464,9 +479,29 @@ class Cache:
                     sz += len(chunk)
                     h.update(chunk)
                     pt.write(chunk)
-            if self.backend.queue_fts_job(book_id, fmt, pt.name, sz, h.hexdigest()):
-                if not self.backend.fts_has_idle_workers:
-                    break
+            with self.write_lock:
+                self.backend.queue_fts_job(book_id, fmt, pt.name, sz, h.hexdigest())
+                return self.backend.fts_has_idle_workers
+
+        while not self.shutting_down:
+            x = queue.get()
+            if x is None:
+                break
+            if not self.backend.fts_enabled:
+                break
+            has_more = True
+            while has_more and not self.shutting_down and self.backend.fts_enabled:
+                try:
+                    has_more = do_one()
+                except Exception:
+                    import traceback
+                    traceback.print_exc()
+
+    @write_api
+    def queue_next_fts_job(self):
+        if not self.backend.fts_enabled:
+            return
+        self.fts_job_queue.put(True)
 
     @write_api
     def commit_fts_result(self, book_id, fmt, fmt_size, fmt_hash, text, err_msg):
@@ -2321,7 +2356,10 @@ class Cache:
 
     @write_api
     def close(self):
+        self.shutting_down = True
         self.event_dispatcher.close()
+        if self.fts_queue_thread is not None:
+            self.fts_job_queue.put(None)
         from calibre.customize.ui import available_library_closed_plugins
         for plugin in available_library_closed_plugins():
             try:
@@ -2330,6 +2368,9 @@ class Cache:
                 import traceback
                 traceback.print_exc()
         self.backend.shutdown_fts()
+        if self.fts_queue_thread is not None:
+            self.fts_queue_thread.join()
+            self.fts_queue_thread = None
         self.backend.close()
 
     @property

src/calibre/db/fts/pool.py

@@ -9,7 +9,7 @@ import sys
 import traceback
 from contextlib import suppress
 from queue import Queue
-from threading import Thread
+from threading import Thread, Event
 from time import monotonic
 
 from calibre import human_readable
@@ -121,15 +121,15 @@ class Pool:
         self.jobs_queue = Queue()
         self.supervise_queue = Queue()
         self.workers = []
-        self.initialized = False
+        self.initialized = Event()
         self.dbref = dbref
 
     def initialize(self):
-        if not self.initialized:
+        if not self.initialized.is_set():
             self.supervisor_thread = Thread(name='FTSSupervisor', daemon=True, target=self.supervise)
             self.supervisor_thread.start()
             self.expand_workers()
-            self.initialized = True
+            self.initialized.set()
 
     def prune_dead_workers(self):
         self.workers = [w for w in self.workers if w.is_alive()]
@@ -195,8 +195,7 @@ class Pool:
             db.commit_fts_result(result.book_id, result.fmt, result.fmt_size, result.fmt_hash, text, err_msg)
 
     def shutdown(self):
-        if self.initialized:
-            self.initialized = False
+        if self.initialized.is_set():
             self.supervise_queue.put(quit)
             for w in self.workers:
                 w.keep_going = False
@@ -205,6 +204,7 @@ class Pool:
             for w in self.workers:
                 w.join()
             self.workers = []
+            self.initialized.clear()
     # }}}
 
     def do_check_for_work(self):

src/calibre/db/tests/fts_api.py

@@ -85,7 +85,7 @@ class FTSAPITest(BaseTest):
         check(id=2, book=1, format='TXT', searchable_text='a test text2')
         # check closing shuts down all workers
         cache.close()
-        self.assertFalse(fts.pool.initialized)
+        self.assertFalse(fts.pool.initialized.is_set())
 
         # check enabling scans pre-exisintg
         cache = self.new_library()