make resume with jsonl output fault tolerant.

src/wikiq/__init__.py

@@ -624,8 +624,11 @@ class WikiqParser:
         return path.parent / f"{path.stem}.part{part_num}{path.suffix}"
 
     def _open_checkpoint(self, output_file):
-        """Enable checkpointing for the given output file."""
+        """Enable checkpointing for Parquet output only.
-        if (not self.output_jsonl and not self.output_parquet) or output_file == sys.stdout.buffer:
+
+        JSONL doesn't need checkpoint files - resume point is derived from last line.
+        """
+        if not self.output_parquet or output_file == sys.stdout.buffer:
             return
         self.checkpoint_path = get_checkpoint_path(output_file, self.partition_namespaces)
         Path(self.checkpoint_path).parent.mkdir(parents=True, exist_ok=True)
@@ -1481,7 +1484,8 @@ def main():
                         else:
                             resume_point = get_resume_point(output_file, partition_namespaces)
                     else:
-                        resume_point = read_checkpoint(get_checkpoint_path(output_file))
+                        # JSONL: get resume point from last line of file (no checkpoint)
+                        resume_point = get_resume_point(output_file, input_file=filename)
                     if resume_point is not None:
                         if isinstance(resume_point, dict):
                             print(f"Resuming from checkpoint for {len(resume_point)} namespaces", file=sys.stderr)

src/wikiq/resume.py

@@ -10,6 +10,7 @@ This module handles:
 import json
 import os
 import sys
+from collections import deque
 
 import pyarrow.parquet as pq
 
@@ -153,31 +154,71 @@ def cleanup_interrupted_resume(output_file, partition_namespaces):
                 os.remove(temp_output_file)
 
 
-def get_resume_point(output_file, partition_namespaces=False):
+def get_jsonl_resume_point(output_file, input_file=None):
+    """Get resume point from last complete line of JSONL file.
+
+    For .jsonl.d directories, derives the file path from input_file using get_output_filename.
+    """
+    # Handle .jsonl.d directory output
+    if output_file.endswith('.jsonl.d'):
+        if input_file is None:
+            return None
+        if os.path.isdir(output_file):
+            # Import here to avoid circular import
+            from wikiq import get_output_filename
+            jsonl_filename = os.path.basename(get_output_filename(input_file, 'jsonl'))
+            output_file = os.path.join(output_file, jsonl_filename)
+        else:
+            return None
+
+    if not os.path.exists(output_file):
+        return None
+
+    try:
+        with open(output_file) as f:
+            # Stream through file, keeping only last 2 lines in memory
+            for line in reversed(deque(f, maxlen=2)):
+                try:
+                    record = json.loads(line)
+                    return (record['articleid'], record['revid'])
+                except (json.JSONDecodeError, KeyError):
+                    continue
+        return None
+    except IOError as e:
+        print(f"Warning: Could not read {output_file}: {e}", file=sys.stderr)
+        return None
+
+
+def get_resume_point(output_file, partition_namespaces=False, input_file=None):
     """
     Find the resume point(s) from existing output.
 
-    First checks for a checkpoint file (fast), then falls back to scanning
+    For JSONL: reads last line of file (no checkpoint needed).
-    the parquet output (slow, for backwards compatibility).
+    For Parquet: checks checkpoint file, falls back to scanning parquet.
 
     Args:
         output_file: Path to the output file.
         partition_namespaces: Whether the output uses namespace partitioning.
+        input_file: Path to input file (needed for .jsonl.d directory output).
 
     Returns:
         For single files: A tuple (pageid, revid) or (pageid, revid, part), or None.
         For partitioned: A dict mapping namespace -> (pageid, revid, part), or None.
     """
+    # For JSONL, read resume point directly from last line (no checkpoint needed)
+    if output_file.endswith('.jsonl') or output_file.endswith('.jsonl.d'):
+        result = get_jsonl_resume_point(output_file, input_file)
+        if result:
+            print(f"Resume point found from JSONL: pageid={result[0]}, revid={result[1]}", file=sys.stderr)
+        return result
+
+    # For Parquet, use checkpoint file (fast)
     checkpoint_path = get_checkpoint_path(output_file, partition_namespaces)
     checkpoint_result = read_checkpoint(checkpoint_path, partition_namespaces)
     if checkpoint_result is not None:
         print(f"Resume point found in checkpoint file {checkpoint_path}", file=sys.stderr)
         return checkpoint_result
 
-    # For JSONL, only checkpoint-based resume is supported
-    if output_file.endswith('.jsonl'):
-        return None
-
     # Fall back to scanning parquet (slow, for backwards compatibility)
     print(f"No checkpoint file found at {checkpoint_path}, scanning parquet output...", file=sys.stderr)
     try: