On 10/09/2015 02:12 PM, Michael Paquier wrote:
> On Fri, Oct 9, 2015 at 8:25 AM, Michael Paquier
> <michael.paquier@gmail.com> wrote:
>> On Thu, Oct 8, 2015 at 11:28 PM, Amir Rohan wrote:
>>> Wouldn't this work?
>>> 1) start timer
>>> 2) Grab pg_stat_replication.sent_location from master
>>> 3) pg_switch_xlog() # I /think/ we want this, could be wrong
>>
>> For a warm standby, you would want that, but this depends on two factors:
>> - The moment master completes archiving of this segment
>> - The moment standby restores it.
>> On slow machines, those two things become by far the bottleneck,
>> imagine a PI restricted on I/O with a low-class SD card in the worst
>> case (I maintain one, with a good card, still the I/O is a
>> bottleneck).
>>
>>> 4) Poll slave's pg_last_xlog_replay_location() until LSN shows up
>>> 5) stop timer
>>
>> That's not really solid, there is an interval of time between the
>> moment the LSN position is taken from the master and the standby. An
>> accurate method is to log/store on master when a given WAL position
>> has been flushed to disk, and do the same on slave at replay for this
>> LSN position. In any case this is doing to flood badly the logs of
>> both nodes, and as the backend cares about the performance of
>> operations in this code path we won't want to do that anyway.
>>
>> To make it short, it seems to me that simply waiting until the LSN a
>> test is waiting for has been replayed is just but fine for this set of
>> tests to ensure their run consistency, let's not forget that this is
>> the goal here.
>
> In terms of features, it seems that this patch has everything it needs
> to allow one to design tests to work on both Linux and Windows, and it
> is careful regarding CVE-2014-0067. Thoughts about moving that as
> "Ready for committer"?
>
Ok, I've put myself down as reviewer in cfapp. I don't think I can
provide any more useful feedback that would actually result in changes
at this point, but I'll read through the entire discussion once last
time and write down final comments/notes. After that I have no problem
marking this for a committer to look at.
Amir
