[Pgpool-hackers] path to follow master after a failover

[Tatsuo Ishii]

>> - IMO we need finer control over which node should be
>>   degenerated. Probably we should have a new flag for each
>>   backend something like this:
>>
>>   backend_option0 = opt_value where opt_value is one of:
>>
>>   DEGENRATE_IF_NEEDED: degenrate whenever pgpool-II thinks
>>   needed. This is same behavior of 3.0 or before.
>>
>>   NEVER_DEGENRATE: never degerate this node.
>>
>>   DEGENERATE_IF_NOT_PROMOTED: in the master/slave mode, degenrate the
>>   if it's not chosen as NEVER_DEGENRATE: never degerate this nodethe promoting node.
>>   (I'm not sure this should apply to slony mode)
> 
> Not sure that we really need all of that. In my opinion, we binary use
> or not use autorecovery of slaves. What's a reason where we could decide
> to not recover a particular slave ?

There are at least two use cases:

1) For some reasons (for example, protected by other HA solution such
   as heartbeat) we do not want to degenerate the node(probably it's
   the master/primary node). We could have yet another switch
   "never_degenerate_master_node" or some such, but IMO my proposal is
   more general and covers the case.

2) Mostly read only huge database which has multiple standbys. The
   database is so huge, we don't wan't to recover non promoted
   standbys until the maintenance time.
--
Tatsuo Ishii
SRA OSS, Inc. Japan
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