contextCSN of subordinate syncrepl DBs
by Rein Tollevik
I've been trying to figure out why syncrepl used on a backend that is
subordinate to a glue database with the syncprov overlay should save the
contextCSN in the suffix of the glue database rather than the suffix of
the backend where syncrepl is used. But all I come up with are reasons
why this should not be the case. So, unless anyone can enlighten me as
to what I'm missing, I suggest that this be changed.
The problem with the current design is that it makes it impossible to
reliably replicate more than one subordinate db from the same remote
server, as there are now race conditions where one of the subordinate
backends could save an updated contextCSN value that is picked up by the
other before it has finished its synchronization. An example of a
configuration where more than one subordinate db replicated from the
same server might be necessary is the central master described in my
previous posting in
http://www.openldap.org/lists/openldap-devel/200806/msg00041.html
My idea as to how this race condition could be verified was to add
enough entries to one of the backends (while the consumer was stopped)
to make it possible to restart the consumer after the first backend had
saved the updated contextCSN but before the second has finished its
synchronization. But I was able to produce it by simply add or delete
of an entry in one of the backends before starting the consumer. Far to
often was the backend without any changes able to pick up and save the
updated contextCSN from the producer before syncrepl on the second
backend fetched its initial value. I.e it started with an updated
contextCSN and didn't receive the changes that had taken place on the
producer. If syncrepl stored the values in the suffix of their own
database then they wouldn't interfere with each other like this.
There is a similar problem in syncprov, as it must use the lowest
contextCSN value (with a given sid) saved by the syncrepl backends
configured within the subtree where syncprov is used. But to do that it
also needs to distinguish the contextCSN values of each syncrepl
backend, which it can't do when they all save them in the glue suffix.
This also implies that syncprov must ignore contextCSN updates from
syncrepl until all syncrepl backends has saved a value, and that
syncprov on the provider must send newCookie sync info messages when it
updates its contextCSN value when the changed entry isn't being
replicated to a consumer. I.e as outlined in the message referred to above.
Neither of these changes should interfere with ordinary multi-master
configurations where syncrepl and syncprov are both use on the same
(glue) database.
I'll volunteer to implement and test the necessary changes if this is
the right solution. But to know whether my analysis is correct or not I
need feedback. So, comments please?
--
Rein Tollevik
Basefarm AS
14 years
dITStructureRules/nameForms in subschema subentry for informational purpose
by Michael Ströder
HI!
Discussed this very briefly with Howard at LDAPcon 2007 based on an idea
of Steve:
Support for dITStructureRules and nameForms is still in OpenLDAP's TODO.
In the meanwhile slapd could accept definitions for both in slapd.conf
and simply pass them on to a schema-aware LDAP client for informational
purpose without enforcing them. Same function like rootDSE <file> in
slapd.conf.
Opinions?
Ciao, Michael.
--
Michael Ströder
E-Mail: michael(a)stroeder.com
http://www.stroeder.com
14 years, 8 months
slapadd performance degradation from 2.3.43 to 2.4.12
by Ralf Haferkamp
Hi,
While doing a few slapadd testruns comparing the RE23 with the RE24 version I
ran into a strange issue. I ran test with different LDIFs (100k, 500k and
1000k Entries) and especially with the 500k and 1000k LDIF, slapadd from
2.3.43 was significantly faster than the 2.4.12 version.
2.3.43 loaded the 500k database in 13m54s while it took 33m49s with 2.4.12.
The 1000k testcase to 29m41s on 2.3 (still faster than the 500k on 2.4). I
didn't finish the 2.4 run with the 1000k database I stopped it after about an
hour.
I used exactly the same configuration on exactly the same hardware/os for the
tests (a HP Proliant DL 580 G3 with 4 3.33GHz Xeons, 8GB of RAM, SLES10-SP2,
ext3 filesystem). BerkelyDB Version was 4.5.20 with the following DB_CONFIG:
set_cachesize 0 4294967295 1
set_lg_regionmax 262144
set_lg_bsize 2097152
cachesize in slapd.conf was large enough to hold the entire database and tool-
threads was set to 4.
I did some profiling (with valgrinds callgrind tool) to find out where all the
time is spend and it revealed that 2.4 spend a significantly larger amount of
systime in the pwrite() function than 2.3. Most of that seemed to come from
the bdb_tool_trickle_task() that calls libdb's memp_trickle() function.
Just to verify this I ran a testbuild with the trickle_task disabled(). And
slapadd's performance was back to a normal level, comparable to the 2.3.43
release.
AFAIK the trickle_task() was introduced into 2.4 to increase slapadd
throughput but has exactly the opposite effect on my test system. Did anybody
else make similar experiences? Or do you see anything thats obviously wrong
with my testcases?
--
Ralf
15 years
moduleload <statically linked module>
by Hallvard B Furuseth
Could we make "moduleload <statically linked module>" valid if the
module name contains no "." or directory separator? Or introduce a
new "module" keyword which works that way?
That would simplify slapd.conf scripting, and documentation examples
could simply include moduleload and would be correct without any
caveats about whether the modules are statically linked.
Also, moduleload seems to take an undocumented argument list which
is passed to the module init routine. See module.c:module_load().
That ought to work whether or not the module is dynamically loaded.
I don't think it does now.
--
Hallvard
15 years
OpenLDAP 2.4.x: change of shared library version every release
by Xin LI
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Hi,
I just noticed that 2.4.12 and 2.4.13 both bumped the shared library
version. Did we actually changed the API that makes the version bump
necessary?
Cheers,
- --
Xin LI <delphij(a)delphij.net> http://www.delphij.net/
FreeBSD - The Power to Serve!
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15 years
Leak in syncprov_matchops()?
by Pierangelo Masarati
==30484== 1,371 bytes in 43 blocks are definitely lost in loss record 12
of 13
==30484== at 0x40053C0: malloc (vg_replace_malloc.c:149)
==30484== by 0x8258EFB: ber_memalloc_x (memory.c:226)
==30484== by 0x80A743C: ch_malloc (ch_malloc.c:54)
==30484== by 0x81747E5: bdb_entry_get (id2entry.c:421)
==30484== by 0x8104832: overlay_entry_get_ov (backover.c:365)
==30484== by 0x81FF53A: syncprov_matchops (syncprov.c:1151)
==30484== by 0x820175E: syncprov_op_mod (syncprov.c:1870)
==30484== by 0x8104F47: overlay_op_walk (backover.c:660)
==30484== by 0x810517C: over_op_func (backover.c:722)
==30484== by 0x81052AA: over_op_delete (backover.c:774)
==30484== by 0x80FA708: syncrepl_entry (syncrepl.c:2283)
==30484== by 0x80F5AC5: do_syncrep2 (syncrepl.c:877)
==30484== by 0x80F72C2: do_syncrepl (syncrepl.c:1301)
==30484== by 0x8086439: connection_read_thread (connection.c:1218)
==30484== by 0x8222E50: ldap_int_thread_pool_wrapper (tpool.c:663)
==30484== by 0xDEB46A: start_thread (in /lib/libpthread-2.5.so)
==30484== by 0x423FDBD: clone (in /lib/libc-2.5.so)
This was the result of a concurrency test while testing MMR. Not sure
about how to reproduce it, but I've seen lots of deadlock resolutions,
so probably there's some exception we're not handling fine with respect
to memory allocation (HEAD as of today).
p.
Ing. Pierangelo Masarati
OpenLDAP Core Team
SysNet s.r.l.
via Dossi, 8 - 27100 Pavia - ITALIA
http://www.sys-net.it
-----------------------------------
Office: +39 02 23998309
Mobile: +39 333 4963172
Fax: +39 0382 476497
Email: ando(a)sys-net.it
-----------------------------------
15 years
valgrind complains about use of uninitialized var
by Pierangelo Masarati
==30484== Conditional jump or move depends on uninitialised value(s)
==30484== at 0x81740C2: bdb_entry_release (id2entry.c:271)
Apparently, boi_flags is not initialized. Where should it be
initialized, and how, is still obscure to me (HEAD as of today).
p.
Ing. Pierangelo Masarati
OpenLDAP Core Team
SysNet s.r.l.
via Dossi, 8 - 27100 Pavia - ITALIA
http://www.sys-net.it
-----------------------------------
Office: +39 02 23998309
Mobile: +39 333 4963172
Fax: +39 0382 476497
Email: ando(a)sys-net.it
-----------------------------------
15 years
Strange issue with contextCSN
by Pierangelo Masarati
I'm running concurrency tests of MMR, and I see some strange issues:
1) loss of sync after multi-concurrent load (multiple concurrent ops on
each server, and modifications to the same data subset on all servers,
in order to trigger conflicts). I'm still trying to see if there is any
pattern or clue about what failed (like finding some explanation in the
logs). This happens once in a while after many operations. I don't
expect this to be necessarily a bug; it might be the consequence of
conflicts. Of course, it would be nice if slapd allows to clearly
identify where the conflict occurred, to support manual resolution.
2) loss of sync after single-concurrent load (multiple concurrent ops on
a single server). This is really inesplicable (to me), as there should
be no conflict. The only possible explanation I see (but need to
investigate further) is that an entry is added on a server, sync'd to
another one and, in the meanwhile, deleted on the first one before its
own sync gets back. This happens very seldom.
3) whay puzzled me a bit is that when I load a single server, I'd expect
to end up with a single contextCSN containing the SID of that server.
This is correct for the server I load, but the others, even when they
get correctly sync'd, contain a contextCSN for each server in the MMR
pool, and the contextCSN with the other SIDs don't get propagated to the
server that was loaded. It's not clear why those CSNs are generated,
and how they get into the loop and propagate between servers that do not
receive direct modifications.
4) another thing that puzzled me a bit is that in some cases, when all
servers are loaded, and the contextCSNs are one for each SID and the
same in all of the servers, they are sorted randomly, and differently;
for example:
bash-3.2$ diff -u testrun/server2.out testrun/server3.out
--- testrun/server2.out 2008-11-22 17:17:28.000000000 +0100
+++ testrun/server3.out 2008-11-22 17:17:28.000000000 +0100
@@ -2497,8 +2497,8 @@
associatedDomain: example.com
entryCSN: 20081122161630.753152Z#000000#001#000000
contextCSN: 20081122161708.935242Z#000000#001#000000
-contextCSN: 20081122161658.195350Z#000000#002#000000
contextCSN: 20081122161658.193983Z#000000#003#000000
+contextCSN: 20081122161658.195350Z#000000#002#000000
Not a big deal (except for the need to sort values to compare them), but
I'd expect them to be exactly in the same order...
I'm going to pack my suite of tests and put them on ftp.openldap.org
(and eventually add them to OpenLDAP's test suite, specifically meant to
test MMR), but first I need to polish them a little bit and enucleate
those that present issues, in order to open specific ITSes.
p.
Ing. Pierangelo Masarati
OpenLDAP Core Team
SysNet s.r.l.
via Dossi, 8 - 27100 Pavia - ITALIA
http://www.sys-net.it
-----------------------------------
Office: +39 02 23998309
Mobile: +39 333 4963172
Fax: +39 0382 476497
Email: ando(a)sys-net.it
-----------------------------------
15 years
