The current callers of ovsdb_log_open() always want to lock the file if
they are accessing it for read/write access. An upcoming commit will add
a new caller that does not fit this model (it wants to lock the file
across a wider region) and so the caller should be able to choose whether
to do locking. This commit adds that ability.
Also, get rid of the use of <fcntl.h> flags to choose the open mode, which
has always seemed somewhat crude and which this change would make even
cruder.
When a new record is inserted into a database, ovsdb logs the values of all
of the fields in the record. However, often new records have many columns
that contain default values. There is no need to log those values, so this
commit causes them to be omitted.
As a side effect, this also makes "ovsdb-tool show-log --more --more"
output easier to read, because record insertions print less noise. (Adding
--more --more to this command makes it print changes to database records.
The --more option will be introduced in an upcoming commit.)
The idea here is that transaction comments get copied to the ovsdb-server's
transaction log, which can then make it clear later why a particular change
was made to the database, to ease debugging.
An upcoming commit will add support for replicating tables across JSON-RPC
connection. As a prerequisite ovsdb itself must support basic replication.
This commit adds that support and then reimplements the ovsdb file storage
in terms of that replication.
