Bug 9034

Created attachment 2962 [details]
Patch fixing -wal and -shm sqlite file deletion

When daemonizing the PR service the -wal and -shm sqlite files are being deleted, although they should never be (see https://www.sqlite.org/wal.html and https://www.sqlite.org/tempfiles.html).

While the daemonized process keeps the file descriptors open (seen from /prid<pid>/fd on linux) and thus a clean exit does not loose any data, a power outage would loose all data in the WAL as the -wal file is unavailable when sqlite does its recovery, so even committed transactions would be lost.

Removing these files also breaks sqlite collaboration between processes and furthermore prevents taking proper backups without stopping the PR service (e.g., with sqlite3 shell's ".backup" command).

The reason the files are deleted is that the DB connection is opened in the initial process, before forking for daemonization. When the DB connection is closed by the exiting parent processes it can delete the -wal and -shm files if it considers itself to be the last connection to the DB. This is easily fixed by opening the DB connection after all forking.

The attached patch does this (on top of jethro branch). With this I have been able to start the PR Service in daemon mode and the -wal and -shm files do exist and I can take proper backups.