ITS8100: What to do about a fresh accesslog DB when in delta-sync MMR node

[Quanah Gibson-Mount]

There's a general issue with using delta-sync MMR that needs some 
resolution (It's causing some considerable pain for customers): It is 
possible to put the entire system into endless fallbacks until a new and/or 
reloaded node gets a write operation.  The general problem is that when an 
existing master queries the new/reloaded master's accesslog DB, zero 
entries are returned. This then triggers the fallback.  This happens up 
util such a time as the new/reloaded master gets a direct write op.  I've 
worked around it in general by immediately doing a no-op on the primary db 
(ldapmodify/replace an attribute value with its own value), but it would be 
nice to be able to bring new MMR nodes online or be able to reload MMR 
nodes for if they get out of sync, etc, without causing this sync fallback 
issue.  There is no clear solution at the moment on what to do about zero 
results from the accesslog in the delta-sync MMR scenario.  Proposals 
welcome. ;)

--Quanah
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Quanah Gibson-Mount
Platform Architect
Zimbra, Inc.
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