Use pipe worker for the main render process

src/calibre/gui2/viewer/convert_book.py

@@ -14,9 +14,11 @@ from hashlib import sha1
 
 from calibre import walk
 from calibre.constants import cache_dir, iswindows
+from calibre.ptempfile import TemporaryFile
 from calibre.srv.render_book import RENDER_VERSION
-from calibre.utils.ipc.simple_worker import fork_job
+from calibre.utils.ipc.simple_worker import start_pipe_worker
 from calibre.utils.lock import ExclusiveFile
+from calibre.utils.serialize import msgpack_dumps
 from calibre.utils.short_uuid import uuid4
 from polyglot.builtins import as_bytes, as_unicode, iteritems
 
@@ -120,10 +122,16 @@ def prepare_convert(temp_path, key, st):
 
 def do_convert(path, temp_path, key, instance):
     tdir = os.path.join(temp_path, instance['path'])
-    fork_job('calibre.srv.render_book', 'render_for_viewer', args=(
-        path, tdir, {'size': instance['file_size'], 'mtime': instance['file_mtime'], 'hash': key},
-        ), timeout=3000, no_output=True
-    )
+    with TemporaryFile('log.txt') as logpath, open(logpath, 'w+b') as logf:
+        p = start_pipe_worker('from calibre.srv.render_book import viewer_main; viewer_main()', stdout=logf, stderr=logf)
+        p.stdin.write(msgpack_dumps((
+            path, tdir, {'size': instance['file_size'], 'mtime': instance['file_mtime'], 'hash': key},
+            )))
+        p.stdin.close()
+    if p.wait() != 0:
+        with lopen(logpath, 'rb') as logf:
+            raise Exception('Failed to convert book: {} with errors:\n{}'.format(
+                path, logf.read().decode('utf-8', 'replace')))
     size = 0
     for f in walk(tdir):
         size += os.path.getsize(f)

src/calibre/srv/render_book.py

@@ -861,5 +861,11 @@ def render_for_viewer(path, out_dir, book_hash):
     )
 
 
+def viewer_main():
+    stdin = getattr(sys.stdin, 'buffer', sys.stdin)
+    args = msgpack_loads(stdin.read())
+    render_for_viewer(*args)
+
+
 if __name__ == '__main__':
     render_for_viewer(sys.argv[-2], sys.argv[-1], None)