On 1/14/2011 3:09 PM, Steve Singer wrote:
> On 11-01-13 04:13 PM, Christopher Browne wrote:
>>  Bug #173 is about the notion of extending Slonik to allow one to
>>  ask a Slonik script to error out upon running into particular
>>  conditions.
>>
>>  These "ABORT" statements could be used to guard a script; if it runs
>>  into unacceptable pre-conditions, it may terminate before it does any
>>  damage to the cluster.
>>
>>  I suggest the following, as starting points:
>>
>>  - Behind by...
>>      ->= 5 events
>>      ->= 30 seconds
>>
>>     ABORT IF BEHIND ( PROVIDER = 1, RECEIVER = 3, SECONDS = 30, comment = 'Behind by 30 seconds', return=1);
>>     ABORT IF BEHIND ( PROVIDER = 1, RECEIVER = 3, EVENT = 5, comment= 'Behind by 5 events', return=2);
>>
>
> I like this idea in principal:
> -Do you mean provider or do you really mean origin?
> -I think EVENT should be 'EVENT COUNT' or something to indicate that we
> are checking the number of events it is behind, versus ('has the
> receiver received event number 5')

Another important detail would be to ask

     "Are there any non-SYNC events outstanding?"

Scripts that modify the cluster configuration may not care about how far 
a node is behind in data, but definitely need to assume that the current 
configuration is stable and not altered underneath by older events, that 
haven't propagated through the cluster.


Jan

-- 
Anyone who trades liberty for security deserves neither
liberty nor security. -- Benjamin Franklin