# HG changeset patch
# User Jun Wu <quark@fb.com>
# Date 1468956851 -3600
# Node ID bc73b80baf983c1f822b7eddb16684905c34cd86
# Parent  9a6bb365786159343633fd8c27bef6cc795fc7ae
SqliteRevMap: wait indefinitely for database lock

Python sqlite has 5 seconds timeout by default, which means if a writer holds
the lock, and the second writer will error out after 5 seconds.

In our use-case, it makes sense to just wait. However, sqlite does not support
waiting forever (see sqlite3_busy_timeout). Therefore use a while loop to
workaround.

diff --git a/hgsubversion/maps.py b/hgsubversion/maps.py
--- a/hgsubversion/maps.py
+++ b/hgsubversion/maps.py
@@ -662,7 +662,14 @@ class SqliteRevMap(collections.MutableMa
         if self._db is None:
             self._opendb()
         with self._db as db:
-            db.execute('BEGIN %s' % mode)
+            # wait indefinitely for database lock
+            while True:
+                try:
+                    db.execute('BEGIN %s' % mode)
+                    break
+                except sqlite3.OperationalError as ex:
+                    if str(ex) != 'database is locked':
+                        raise
             yield db
 
     def _query(self, sql, params=()):