1:29 a.m.
>> And here's some quick stats:
>> $ grep syncrepl CHANGES | grep -v delta | wc -l
>> 76
>>
>> $ grep delta-syncrepl CHANGES | wc -l
>> 7
>>
>> Or syncrepl has had 10x times the issues.
>
> Or syncrepl has 10x the users, more eyes spot more bugs, and is now
> more stable because it has had more fixes? I'm just speculating here,
> but I wouldn't be more confident in product Y because it is mentioned
> less in the change log than product X.
Nope. I've been using syncrepl since it was first released in 2.2. I switched over
the production
ldap servers I was running @ Stanford to syncrepl when 2.3 came out, and found a really
vexing
problem when mass updates occurred (primarily at quarter end when we'd receive 10s
of
thousands of updates due to class enrollment changes). While 1-2 of our 6 replicas would
stay up
to date, the other 4 would fall hours or days behind. I.e., I'm quite familiar with
the issue you are
discussing, because I've been experiencing it for over a decade. Out of this,
delta-syncrepl was
born. I've been using it steadily now for over a decade. I switched Zimbra to it
back in 2007, and
it is deployed at customers world wide, from insallations with 10-20 users to
installations with many
millions of users. Has there been the occassional issue? Yes. But again, the vast
majority of
problems I encounter when investigating problems around replication come from syncrepl
fallback.
There is a very significant fix coming out in 2.4.43 that was found by Zimbra with
syncrepl refresh
when it is interrupted during the refresh phase (ITS#8281).
So, when I talk about replication and reliability in relation to OpenLDAP, this is
something I've been
working with since the early days of OpenLDAP 2.1. It's something that as a part of
my job, I have
to take with the utmost seriousness.
Now, you can ignore my advice if you wish, it doesn't matter to me one way or the
other. But to
me, mission critical systems must be as reliable as possible, and I've only found
that to be the case
with openldap replication when I deploy delta-syncrepl as the primary replication
mechanism.
Thanks for your insight, Quanah, and this is a much more substantial argument now than
doing
'grep -c' on a changelog, and I appreciate the time you spent to make that case.
If we're primarily adding or deleting entire objects, however, not modifying single
attributes,
won't delta-syncrepl just fall back to syncrepl anyway?
And this still doesn't change the fact that I'm now going to have to spin up 10-20
LDAP replicas on
a single machine to get around the single-threaded replication engine problem.
Mark.
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