[pcp] pcp updates: pmlogger semantics change, 1st round of strtoint64 changes

[Marko Myllynen]

Hi Ken,

apologies for reviving this old thread but I noticed something that
might perhaps still be improved, at least in a theory..

On 2015-10-15 09:22, Marko Myllynen wrote:
> On 2015-10-15 09:15, Ken McDonell wrote:
>> Some review eyes here would be appreciated.
>>
>> Ken McDonell (9):
>>       libpcp: extend __pmAF* family with __pmAFsetup
>>       pmlogger: change semantics for first logging operation
>>       qa: many changes for pmlogger "log early" semantic change

Let us consider the following archive created with the latest PCP code:

$ pmdumplog -a ...
...
Temporal Index
             Log Vol    end(meta)     end(log)
10:05:09.228       0          132          132
10:05:09.248       0          351          268
10:05:15.248       0          503          484

[136 bytes]
10:05:09.228  2.3.3 (pmcd.pmlogger.host): inst [17779 or "17779"] value
"localhost"
              2.3.0 (pmcd.pmlogger.port): inst [17779 or "17779"] value 4331
              2.3.2 (pmcd.pmlogger.archive): inst [17779 or "17779"]
value "/tmp/8LdWEN.localhost"

[72 bytes]
10:05:09.248  60.2.2 (kernel.all.runnable): value 1
              60.0.4 (disk.dev.read): inst [0 or "sda"] value 59546

[72 bytes]
10:05:11.248  60.2.2 (kernel.all.runnable): value 2
              60.0.4 (disk.dev.read): inst [0 or "sda"] value 59546

[72 bytes]
10:05:13.248  60.2.2 (kernel.all.runnable): value 1
              60.0.4 (disk.dev.read): inst [0 or "sda"] value 59546

[72 bytes]
10:05:15.248  60.2.2 (kernel.all.runnable): value 1
              60.0.4 (disk.dev.read): inst [0 or "sda"] value 59546
$

Clients which fetch and report the metrics for the first time will see
the pmcd.* related metrics at 09.228 but not the user recorded metrics
as they start a bit later at 09.248. So a client is slightly "off-sync"
e.g. with pmval -a ... -r the reported values are one value "behind"
what a user might expect.

This caught my attention when I was testing pmrep archive handling with
tiny archives with 1s interval, do you think this kind of tweaking would
be possible and worthwhile?

Thanks,

-- 
Marko Myllynen