krb5 1.13 Replication enhancements

Sat Oct 11 18:48:12 EDT 2014

I found an issue with kdb_first_sno not being set during a DB restore which
contributed to extra resyncs. Now, I believe all my prior 1.12 contributions
are now covered by these patches.

Updated wiki:
https://github.com/rbasch/krb5/wiki/1.13-Replication-enhancements

Revised commits (pursuant to "git rebase"):

https://github.com/rbasch/krb5/commit/d9ec51d87f9fc4e1592423bf7562895fad2752
c2  first_sno fix

https://github.com/rbasch/krb5/commit/f4ed3369f2c7a0ec6d834f46677d8ffc4e2223
f4  notify slaves

From: Richard Basch [mailto:basch at alum.mit.edu] 
Sent: Wednesday, October 8, 2014 9:42 PM
To: 'Richard Basch'; 'Greg Hudson'; 'tlyu at mit.edu'; 'krbdev at mit.edu'
Cc: 'kayla.c.harrison at gmail.com'
Subject: RE: krb5 1.13 Replication enhancements

I found a problem in kproplog pursuant to my "first_sno fix".

Revised wiki:
https://github.com/rbasch/krb5/wiki/1.13-Replication-enhancements

Revised commits (pursuant to "git rebase"):

https://github.com/rbasch/krb5/commit/d3189af4fc65569881d6f553d8ab34f4357946
35  first_sno fix

https://github.com/rbasch/krb5/commit/4fbe0f4b8f5aa771bc7173725f9303a3a5b627
11  notify slaves

From: Richard Basch [mailto:basch at alum.mit.edu] 
Sent: Thursday, October 2, 2014 8:25 PM
To: 'Richard Basch'; 'Greg Hudson'; 'tlyu at mit.edu'; 'krbdev at mit.edu'
Cc: 'kayla.c.harrison at gmail.com'
Subject: RE: krb5 1.13 Replication enhancements

Revised commits (in particular, the second one only differs in the syslog
output generated, not in the core functionality). I was concerned about
excessive logging by kadmind's servicing lots of slaves, so instead of
indicating each slave being notified (which was useful during debugging),
merely indicate the number of slaves being notified (being notified does not
mean they "understand" the notification or will check-in).

https://github.com/rbasch/krb5/commit/ce238c4a19e117caedc7ce53f4780270b86d52
1c      first_sno fix

https://github.com/rbasch/krb5/commit/1bf5b212392ff2679250fcb3d3f197fee3ced3
e1      notify slaves

I have also documented an alternate approach to implementing the feature in
my Wiki, but it is far too involved for me to pursue. MIT should decide if
they want to keep the separation of programs as it stands today, in which
case this patch is probably among the better implementations possible.

From: Richard Basch [mailto:basch at alum.mit.edu] 
Sent: Wednesday, October 1, 2014 9:22 PM
To: 'Greg Hudson'; 'tlyu at mit.edu'; 'krbdev at mit.edu'
Cc: 'kayla.c.harrison at gmail.com'; 'Richard Basch'
Subject: krb5 1.13 Replication enhancements

I have uploaded my commits to github (I am still testing, but I am
reasonably in my git commit)

See https://github.com/rbasch/krb5/wiki/1.13-Replication-enhancements

Basically, this uplifts the 1.13-beta1 code base to the same level as I
previously provided as an enhancement for 1.12, specifically:

- Do not require the DB first_sno to be present in the ulog (this avoids
extraneous db resyncs to downstream slaves)

- Implement downstream slave notification when ulog is updated.

The following are my GIT commits, but it may be better to reference the
commits via the wiki in case I have to apply another fix and rebase.

Allow kdb_first_* not to be present in the ulog

https://github.com/rbasch/krb5/commit/ce238c4a19e117caedc7ce53f4780270b86d52
1c      

Notify downstream slaves of pending ulog updates

https://github.com/rbasch/krb5/commit/db0c450f6c09f4623bff3c3aff16794ba4e2c7
63      

-----Original Message-----

From: Richard Basch [ <mailto:basch at alum.mit.edu> mailto:basch at alum.mit.edu]

Sent: Tuesday, September 30, 2014 3:26 PM

To: 'Greg Hudson'; 'tlyu at mit.edu'

Cc: 'kayla.c.harrison at gmail.com'

Subject: RE: krb5-1.13-beta1 iprop

Yeah, re #2... I originally went through all the code which I could find
which pertained to the ulog parsing... the only other change I had was in
kproplog at the time so that it wouldn't overrun a missing entry. I had
added some defensive checks in my original code to only allow for 1 missing
entry, but upon a ulog wrap, it would reset the number.

I'll try to re-incorporate all of this...

-----Original Message-----

From: Greg Hudson [ <mailto:ghudson at mit.edu> mailto:ghudson at mit.edu]

Sent: Tuesday, September 30, 2014 2:58 PM

To: Richard Basch;  <mailto:tlyu at mit.edu> tlyu at mit.edu

Cc:  <mailto:kayla.c.harrison at gmail.com> kayla.c.harrison at gmail.com

Subject: Re: krb5-1.13-beta1 iprop

On 09/30/2014 01:30 PM, Richard Basch wrote:

> If you want, I believe I can have patches for 1.13 beta in the next 

> couple days and publish them to github. In essence, there should be no 

> changes to command-line arguments at this point, since you have iprop 

> tree-based propagation already available.

> 

> Will that help?

Yes, that will provide a better starting point.

> Preliminary testing also suggests that it may be causing an extraneous 

> full resync (I had this problem in one of my early implementations 

> too). I suspect you are resetting the first_sno when you get your 

> first ulog entry (my 1.12 patches avoided resetting the first_sno 

> until it wrapped so that the first "dump/restore" would not be 

> followed by a second one if there were no additional ulog entries to 

> apply).  I am not certain if this is what is going on, but some 

> preliminary testing suggested such (again, I haven't looked at the 

> 1.13

code yet).

See item #2 in

<http://k5wiki.kerberos.org/wiki/Projects/Hierarchical_iprop#Related_problem
s>
http://k5wiki.kerberos.org/wiki/Projects/Hierarchical_iprop#Related_problems

Your implementation had a workaround for this issue, but it broke (at

least) the detection of ulog size changes.  I ran out of time to design a
better workaround.