Question

I’m using Tokyo Cabinet with the tc module in python. I store my data in the TDB format. I expected the table to block only for the duration of a write. Unfortunately, I see that when the file is open with in the “writer mode”, other processes cannot read from it. Is that a standard behaviour, wrappers problem, or am I doing something wrong? Or maybe there are other cases when the operations are blocked?

Answer 1

According to specification:

Tokyo Cabinet provides two modes to
connect to a database: “reader” and
“writer”. A reader can perform
retrieving but neither storing nor
deleting. A writer can perform all
access methods. Exclusion control
between processes is performed when
connecting to a database by file
locking. While a writer is connected
to a database, neither readers nor
writers can be connected. While a
reader is connected to a database,
other readers can be connect, but
writers can not. According to this
mechanism, data consistency is
guaranteed with simultaneous
connections in multitasking
environment.

You have either create and close writer for each write operation or use Tokyo Tyrant to provide concurrent access.