Re: Wait events monitoring future development

2016-08-09 11:49 GMT+09:00 Joshua D. Drake <jd@commandprompt.com>:
> On 08/08/2016 07:37 PM, Bruce Momjian wrote:
>>
>> On Tue, Aug  9, 2016 at 02:06:40AM +0000, Tsunakawa, Takayuki wrote:
>>>
>>> I hope wait event monitoring will be on by default even if the overhead
>>> is not
>>> almost zero, because the data needs to be readily available for faster
>>> troubleshooting.  IMO, the benefit would be worth even 10% overhead.  If
>>> you
>>> disable it by default because of overhead, how can we convince users to
>>> enable
>>> it in production systems to solve some performance problem?  I’m afraid
>>> severe
>>> users would say “we can’t change any setting that might cause more
>>> trouble, so
>>> investigate the cause with existing information.”
>>
>>
>> If you want to know why people are against enabling this monitoring by
>> default, above is the reason.  What percentage of people do you think
>> would be willing to take a 10% performance penalty for monitoring like
>> this?  I would bet very few, but the argument above doesn't seem to
>> address the fact it is a small percentage.
>
>
> I would argue it is zero. There are definitely users for this feature but to
> enable it by default is looking for trouble. *MOST* users do not need this.

I used to think of that this kind of features should be enabled by default,
because when I was working at the previous company, I had only few features
to understand what is happening inside PostgreSQL by observing production
databases. I needed those features enabled in the production databases
when I was called.

However, now I have another opinion. When we release the next major release
saying 10.0 with the wait monitoring, many people will start their
benchmark test
with a configuration with *the default values*, and if they see some performance
decrease, for example around 10%, they will be talking about it as the
performance
decrease in PostgreSQL 10.0. It means PostgreSQL will be facing
difficult reputation.

So, I agree with the features should be disabled by default for a while.

Regards,
--
Satoshi Nagayasu <snaga@uptime.jp>