[ZODB-Dev] Errors running a Stress Test

[Tim Peters]

A quick update on two of the unexpected errors Brandon Ehle is seeing:

> FileStorageError: The database has already been packed to a later time
> or no changes have been made since the last pack

Everyone who has made a comment about this exception (in earlier threads,
not this one) said it was an annoyance.  So current ZODB HEAD has been
changed to stop propagating it.  FileStorage.pack() logs the message now (at
INFO level), but the pack attempt just quits then instead of complaining.

> CorruptedError: zodb.fs:609:transaction with checkpoint flag set

This one is bogus (nothing is actually corrupted).  It's a teensy timing
hole, when a pack overlaps in time with the last step of a concurrent
transaction's commit.  The pack code could get fooled into reading a part of
the file then that's not in its final state (so, yes, it "looks corrupted"
at the time pack reads it, but the commit code hasn't finished writing this
piece of the file then).  This should also be repaired now on current ZODB
HEAD.

Both of these were quite shallow.  The other problems you're seeing probably
aren't related to either of them.