Matthias Andree:
> Am 11.06.2017 um 20:50 schrieb Wietse Venema:
> > Philip Paeps:
> >> On 2017-06-11 14:07:36 (-0400), Wietse Venema <wie...@porcupine.org> wrote:
> >>> Oh, and it will of course open a DB_CONFIG file in whatever happens to
> >>> be the super-user's cwd when they invoke the postmap or postalias
> >>> command, so this is not just a matter of set-gid Postfix commands.
> >>>
> >>> [...]
> >>> - if ((errno = db->set_cachesize(db, 0, dict_db_cache_size, 0)) != 0)
> >>> - msg_fatal("set DB cache size %d: %m", dict_db_cache_size);
> >> Is this change intentional, or did it sneak in? It seems unrelated to
> >> the environment workaround.
> > dbenv->set_cachesize(dbenv, 0, dict_db_cache_size, 0) rejected a
> > call with the Postfix default cache size, and there appears to be
> > no API to find what cache size it would have accepted. Screw it.
> > This library needs to die.
>
> Hi Wietse,
>
> sorry for the techy noise on a users list in this post. There may be
> valid reasons for killing off Berkeley DB, but your using it counter to
> the specs is not one :-)
>
> Explanation: BDB did not reject the size, but it did reject your attempt
> to call db->set_cachesize(...) when the "db" handle was created and
> initialized with a non-NULL dbenv (the db_create(&db, dbenv, 0) call below).
I was calling dbenv->set_cachesize(dbenv, 0, dict_db_cache_size, 0)
as stated in my email above, not db->set_cachesize(...)
Anyway. I found a call dbenv->set_cache_max, introduced somewhere
between DB 4.2 and DB 4.7. That fixes the problem for all but very
old implementations. See postfix-3.3-20170612.
Wietse
> Meaning that:
> You are attempting to set the cache size on the /database/ (not the
> /environment/). The documentation of Berkeley DB states it is an error
> to set the cache size for databases opened within an environment (i. e.
> with a non-null dbenv used in db_create()), because the database uses
> the cache from its environment. Before your patch, there was no
> environment (the dbenv argument was 0 in your db_create() call), so it
> was permissible to call db->set_cachesize().
>
> So instead of calling db->set_cachesize, you now - after introducing the
> environment - need to call dbenv->set_cachesize, (the _env_ being the
> important addition), so that you set the cache size on the environment
> (dbenv variable in your code) instead.
> We've been doing that successfully in bogofilter for more than a decade
> across various Berkeley DB versions.
>
> You can no longer use this:
> *
> https://docs.oracle.com/cd/E17275_01/html/api_reference/C/dbset_cachesize.html
> "Because databases opened within Berkeley DB environments use the cache
> specified to the environment, it is an error to attempt to set a cache
> in a database created within an environment."
>
> You need to use this:
> *
> https://docs.oracle.com/cd/E17275_01/html/api_reference/C/envset_cachesize.html
>
> and you best set it very early, *before* the dbenv->open.
>
>
> Note that the fatal error messages in the code are also misleading here
> in two places - all these marked calls create are the in-memory
> structures ("handles"), the actual environment or database, are only
> created on their respective ->open() calls.
> > + /* Fix 20170611 workaround for undocumented ./DB_CONFIG read. */
> > + if ((errno = db_env_create(&dbenv, 0)) != 0)
> > + msg_fatal("create DB environment: %m");
> here ^^^^^^ I suggest:
>
> msg_fatal("create DB environment handle: %m");
>
> > + dirname_buf = vstring_alloc(100);
> > + if ((errno = dbenv->open(dbenv, sane_dirname(dirname_buf, db_path),
> > + DB_INIT_MPOOL | DB_CREATE | DB_PRIVATE, 0)) != 0)
> > + msg_fatal("open DB environment: %m");
> > + vstring_free(dirname_buf);
> > + if ((errno = db_create(&db, dbenv, 0)) != 0)
> > msg_fatal("create DB database: %m");
>
> here ^^^^^^ I suggest:
>
> msg_fatal("create DB database handle: %m");
>
> HTH
> Matthias
>
>
Wietse
