Improvements to deterministic fix (false triggers) (#3766)

changedetectionio/html_tools.py

@@ -542,29 +542,17 @@ def html_to_text(html_content: str, render_anchor_tag_content=False, is_rss=Fals
     """
     Convert HTML content to plain text using inscriptis.
 
-    CRITICAL FIX: Uses thread-local lxml parsers to prevent race conditions.
+    Thread-Safety: This function uses inscriptis.get_text() which internally calls
+    lxml.html.fromstring() with the default parser. Testing with 50 concurrent threads
+    confirms this approach is thread-safe and produces deterministic output.
 
-    Under high concurrency (50+ threads), lxml's default shared global parser
-    (lxml.html.html_parser) caused non-deterministic parsing behavior, resulting in:
-    - Different text extraction from identical HTML
-    - Different MD5 checksums
-    - False change detection alerts
-
-    This function ensures each thread gets its own HTMLParser instance via
-    thread-local storage, eliminating the race condition.
-
-    See: LXML_THREADING_FIX.md for full details
+    Alternative Approach Rejected: An explicit HTMLParser instance (thread-local or fresh)
+    would also be thread-safe, but was found to break change detection logic in subtle ways
+    (test_check_basic_change_detection_functionality). The default parser provides correct
+    and reliable behavior.
     """
-    from inscriptis import Inscriptis
+    from inscriptis import get_text
     from inscriptis.model.config import ParserConfig
-    from lxml.html import fromstring, HTMLParser
-    import threading
-
-    # Thread-local storage for HTML parser instances to avoid race conditions
-    # under high concurrency. lxml's default parser is a shared global which
-    # causes non-deterministic parsing when used from multiple threads.
-    if not hasattr(html_to_text, '_thread_local'):
-        html_to_text._thread_local = threading.local()
 
     if render_anchor_tag_content:
         parser_config = ParserConfig(
@@ -578,15 +566,7 @@ def html_to_text(html_content: str, render_anchor_tag_content=False, is_rss=Fals
         html_content = re.sub(r'<title([\s>])', r'<h1\1', html_content)
         html_content = re.sub(r'</title>', r'</h1>', html_content)
 
-    # Get or create thread-local parser
-    if not hasattr(html_to_text._thread_local, 'parser'):
-        html_to_text._thread_local.parser = HTMLParser()
-
-    # Parse HTML with thread-local parser to ensure thread-safety
-    html_tree = fromstring(html_content, parser=html_to_text._thread_local.parser)
-
-    # Convert to text using inscriptis
-    text_content = Inscriptis(html_tree, config=parser_config).get_text()
+    text_content = get_text(html_content, config=parser_config)
     return text_content
 
 # Does LD+JSON exist with a @type=='product' and a .price set anywhere?