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Re: Syncrepl: full sync vs. delta
Quanah Gibson-Mount wrote:
--On Wednesday, October 12, 2005 9:35 AM -0700 Howard Chu
Howard Chu wrote:
The assignment of CSNs to operations needs to occur later though. ModRdn
In fact, running test008 with an accesslog overlay that uses a single
mutex on the write ops actually completes faster than normal, because
back-bdb never hits any deadlocks. (Quite a bit faster, 2x at least.)
So I guess this approach is acceptable.
is fine, because it doesn't get a CSN until the backend calls
slap_modrdn2mods. But Add, Delete, and Modify all assign the CSN in the
frontend, before the accesslog's mutex is locked, so CSNs are still
allocated in an uncontrolled order. I'm thinking that all of the
assignments should be invoked from the backend. But that means that
modules that call into backends would need to do the graduate() call
the frontend does right now. I guess the simplest would be for the
accesslog overlay to just replace the CSN the frontend assigned with a
new one. Or add a backend flag "SLAP_DBFLAG_DEFER_CSN" that tells the
frontend not to assign it, because someone else will. ...?
If someone is going to be using delta-syncrepl with a fallback of a
full refresh, don't the CSN's need to be coordinated between the
accesslog backend and their main (bdb/hdb) backend?
Yes, that would be best. Currently they are.
I'm guessing that is what you mean will happen in the
Yes. But that's still too messy; currently only the frontend de-queues
CSNs but there are several places that en-queue them (passwd.c, sasl.c,
various overlays) which means right now those places cause a CSN memory
leak. The cleanest solution now appears to be invoking the CSN
management directly from the backend (like ModRdn does) and removing the
responsibility from the frontend. This seems to be the only way to make
sure slap_graduate_commit_csn() will get called when it's needed.
-- Howard Chu
Chief Architect, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc
OpenLDAP Core Team http://www.openldap.org/project/