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- To: OpenLDAP Devel <firstname.lastname@example.org>
- Subject: OpenLDAP 2.5
- From: Howard Chu <email@example.com>
- Date: Tue, 22 Dec 2009 19:40:45 -0800
- User-agent: Mozilla/5.0 (X11; U; Linux i686; rv:1.9.3a1pre) Gecko/20091218 SeaMonkey/2.0a1pre Firefox/3.0.3
With 2.4.21 out, and hopefully stable enough to promote to the next Stable
release, it's time to feature-freeze 2.4 and prepare for the 2.5 branch. As I
already announced to the OpenLDAP-Committers, we're also planning to switch
from CVS to GIT in mid-January. Commits for 2.5 will begin after we've settled
We haven't really laid out a formal roadmap for 2.5 yet, but I think most of
it has been discussed here or in Development ITSs already.
I would like to be able to resolve all outstanding Development ITSs - we will
either implement them or reject/close them. There are 42 outstanding at the
Likewise for all outstanding ITSs in Software Bugs - many of them have been
deferred because a proper fix would require invasive changes to large parts of
the code base. There are 26 outstanding. With 2.5 beginning we are free to
make these large scale changes.
We should also walk thru the Software Enhancement requests and decide which to
accept and which to reject. Currently there are 37 outstanding.
I also have a number of specific areas I want to see worked on; some of these
are included in the above ITSs but I'll outline them here:
config - this is pretty unwieldy already; syncrepl needs to be moved
outside of the slapd core and into an overlay. That will allow us a lot more
flexibility in configuring while also eliminating a lot of redundant parsing code.
suffixmassage - we at the very least need to be able to point a consumer
at some non-homogeneous suffix in the provider. We may go for complete
librewrite support as well, although at this point I don't see as strong a need.
TLS certs and keys should be stored as LDAP attributes, not pointers to
filesystem locations. This is a prereq to using some of the dynamic cert
generation features of the CA overlay. (This can be troublesome as there may
not be clean APIs for reading certs from memory in all of the TLS APIs we
Disabling individual config attribute values and entries. At the moment
I'm thinking of adding an ";x-disabled" tag to those values.
Using a single-level store for Entries will impact all of the schema
engine as well. I think the simplest solution here is going to be using an
mmap'd file for all of the schema elements.
The actual design of back-mdb still needs to be defined in several areas.
The single-level store approach exposes us to some new failure modes that the
current multi-level backends don't have. (E.g., corruptions due to bad RAM /
wild pointer writes are very likely to get persisted on disk, implicitly.)
The solution I'm considering is based on a mirroring strategy. Every
database will be stored twice on disk: once in the file that is actively
mmap'd into the process, and once in a write-only file. On every intentional
update of a memory page, we will also store a checksum of the page, and
manually write the page to the mirror. If we detect a checksum failure on any
in-memory page we can still retrieve a valid copy from the mirror file. This
of course doubles our potential I/O load, but I don't believe it's any worse
than the load from performing write-ahead logging on a traditional database.
(And yes, mirroring will take the place of writing transaction log files.)
Some of these same considerations apply to the schema storage, but not
entirely. At runtime, the schema is effectively read-only. When we do dynamic
schema changes thru cn=config, all other threads are suspended. For the mmap
purposes, we can mark all of the schema pages as read-only during runtime, and
only make them read-write when cn=config is actually trying to perform an
update. As such, the only sticky issue is dealing with changes made to the
back-config internal files by plain text editors and such.
These are the things I'm interested in. But as always, this Project is driven
forward by the particular interests of each individual contributor. If you
have other ideas you want to pursue, speak up.
-- Howard Chu
CTO, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc/
Chief Architect, OpenLDAP http://www.openldap.org/project/