indygreg created this revision.
Herald added a subscriber: mercurial-devel.
Herald added a reviewer: hg-reviewers.
REVISION SUMMARY
If the Mercurial process fork()s, the Python thread ID remains
unchanged. The previous code for returning a SQLite connection would
recycle the existing connection among all children.
Mercurial can fork() when performing working directory updates.
For reasons I don't fully understand, the recycling of even a
read-only SQLite connection was resulting in Python raising a
"DatabaseError: database disk image is malformed" exception. This
message comes from the bowels of SQLite. I suspect there is some
internal client state in the SQLite database somewhere and having
multiple clients race to update it results in badness. Who knows.
This commit teaches the "get a SQLite connection" logic to also
verify the PID matches before returning an existing connection.
REPOSITORY
rHG Mercurial
REVISION DETAIL
https://phab.mercurial-scm.org/D5411
AFFECTED FILES
hgext/sqlitestore.py
CHANGE DETAILS
diff --git a/hgext/sqlitestore.py b/hgext/sqlitestore.py
--- a/hgext/sqlitestore.py
+++ b/hgext/sqlitestore.py
@@ -76,6 +76,7 @@
)
from mercurial.utils import (
interfaceutil,
+procutil,
storageutil,
)
@@ -1005,17 +1006,18 @@
@property
def _dbconn(self):
-# SQLite connections can only be used on the thread that created
-# them. In most cases, this "just works." However, hgweb uses
-# multiple threads.
-tid = threading.current_thread().ident
+# SQLite connections can only be used on the OS and Python thread that
+# created them. In most cases, this "just works." However, hgweb uses
+# multiple Python threads. And Mercurial may fork. So we need to check
+# global state before returning an existing connection.
+key = (procutil.getpid(), threading.current_thread().ident)
if self._db:
-if self._db[0] == tid:
+if self._db[0] == key:
return self._db[1]
db = makedb(self.svfs.join('db.sqlite'))
-self._db = (tid, db)
+self._db = (key, db)
return db
To: indygreg, #hg-reviewers
Cc: mercurial-devel
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