Re: About the tps explanation of pgbench, please help

Adrian,
I understand you about the tps explain.
What I would like to know is how much the network changed impact on the tps
changes in two cases.

On Wed, Nov 19, 2014 at 10:58 AM, Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com>
wrote:

> On 11/18/2014 05:53 PM, Yanrui Hu wrote:
>
>> Adrian,
>> I saw that in two case, one is 54502 transactions and the other is 13966
>> but that is caused by capacity decrease.
>> And fps is transaction per second, so it's not the transactions but
>> transaction per second, so I don't think the total transactions
>> different has any problem.
>> Please point if my understanding is not correct.
>>
>
> Alright
>
> If:
>
> kph = kilometer per hour = kilometer/hour
>
> 100 km/1 hr = 100 km/hr
>
> 200 km/1 hr = 200 km/hr
>
> If you cover 100 km in 1 hour you have an average rate of speed of 100
> km/hr if you cover 200 km in 1 hour your average rate of speed is 200 km/hr
>
> then
>
> tps = transactions per second = transactions/sec
>
> 54502 transactions/600 sec = 90.84 transactions/sec
>
> 13966 transactions/600 sec = 23.28 transactions/sec
>
> The numbers are not exactly the same as the below, but that is probably
> down to rounding error. They pass the close enough rule though:) Any way
> you look at it, if run a two tests over the same time period and one does
> less transactions then the other you will have different transactions
> rates(tps) You where asking about the why behind the different tps rates,
> the answer is above. In other words you cannot ignore the raw numbers for
> the transactions.
>
>
> My initial plan is to know the impact if I move that db client (also a
>> server runs web server with restful api) out side to internet.
>>
>> On Tue, Nov 18, 2014 at 10:35 PM, Adrian Klaver
>> <adrian(dot)klaver(at)aklaver(dot)com <mailto:adrian(dot)klaver(at)aklaver(dot)com>> wrote:
>>
>> On 11/18/2014 12:33 AM, Yanrui Hu wrote:
>>
>> I am working on a evaluation to put db client outside the
>> datacenter and
>> to know how the network impact on the business.
>> After several round of testing, I have a question regarding to
>> the two
>> tps result in stress output.
>>
>> Test A:
>> Client and DB server exist in same AWS datacenter.
>> transaction type: Custom query
>> scaling factor: 500
>> query mode: simple
>> number of clients: 25
>> number of threads: 25
>> duration: 600 s
>> number of transactions actually processed: 54502
>> tps = 90.814930 (including connections establishing)
>> tps = 204.574432 (excluding connections establishing)
>>
>> Test B:
>> Client and DB server exist in different AWS datacenter (west and
>> east).
>> transaction type: Custom query
>> scaling factor: 500
>> query mode: simple
>> number of clients: 25
>> number of threads: 25
>> duration: 600 s
>> number of transactions actually processed: 13966
>> tps = 23.235705 (including connections establishing)
>> tps = 42.915990 (excluding connections establishing)
>>
>> Its obviously that both tps become lower if client and server do
>> not
>> exist in same datacetner since the network connection have more
>> latency.
>> But I can not explain why the tps that excluding connections
>> establishing is changed so much.
>> For my understanding, tps excluding connections establishing get
>> rid of
>> the time that create socket cost. That means in above two test
>> cases(only network different), the tps excluding connections
>> establishing should be very close, right?
>>
>>
>> Not that I can see from the numbers. In the non-network case you
>> processed 54,502 transactions over 600s and in the network case
>> 13,966 transactions over 600s. Even if you factor out the connection
>> establishment you have fewer transactions over the same time period
>> for the network case. So there is no way the tps can be equivalent.
>> As others have pointed out this due to the effect of network latency
>> on the processing of the queries.
>>
>> You might want to take a look at the Notes section of here:
>>
>> http://www.postgresql.org/__docs/9.3/static/pgbench.html
>> <http://www.postgresql.org/docs/9.3/static/pgbench.html>
>>
>> In particular the different logging options that are available. They
>> may make it easier to see what is going on.
>>
>>
>> Because the database is same
>>
>> and capability is same only network latency is different.
>>
>>
>> --
>> Best Regards,
>>
>> Yanrui Hu (Ray)
>>
>>
>>
>> --
>> Adrian Klaver
>> adrian(dot)klaver(at)aklaver(dot)com <mailto:adrian(dot)klaver(at)aklaver(dot)com>
>>
>>
>>
>>
>> --
>> Best Regards,
>>
>> Yanrui Hu (Ray)
>>
>
>
> --
> Adrian Klaver
> adrian(dot)klaver(at)aklaver(dot)com
>

--
Best Regards,

Yanrui Hu (Ray)