Subject: Re: 9.5 new setting "cluster name" and logging
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From: Evan Rempel <erempel@uvic.ca>
Message-ID: <56C74081.2090605@uvic.ca>
Date: Fri, 19 Feb 2016 08:19:13 -0800
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On 02/19/2016 08:10 AM, Fujii Masao wrote:
> On Sat, Feb 20, 2016 at 12:52 AM, Evan Rempel <erempel@uvic.ca> wrote:
>> On 02/19/2016 05:56 AM, Fujii Masao wrote:
>>> On Fri, Feb 19, 2016 at 7:05 AM, Evan Rempel <erempel@uvic.ca> wrote:
>>>> On 02/18/2016 01:53 PM, Tom Lane wrote:
>>>>> Bruce Momjian <bruce@momjian.us> writes:
>>>>>> On Fri, Jan 29, 2016 at 10:19:45PM -0800, Evan Rempel wrote:
>>>>>>> Now that there is a setting to give a cluster a "name", it would be
>>>>>>> nice to have an escape sequence in the log_line_prefix setting that
>>>>>>> could reference the cluster_name.
>>>>>> Uh, wouldn't the cluster name be the same on every line?  Is that
>>>>>> useful?
>>>>> I guess if you were running multiple clusters and having them all log
>>>>> to the same syslog daemon, there might be multiple clusters' output
>>>>> in the same log ... but we already have ways to disambiguate that case,
>>>>> ie, syslog_ident.  Likewise for Windows' event log.  I don't think we
>>>>> should consider it supported for multiple clusters to be logging into
>>>>> the same plain files.  So yeah, the use case for this seems unclear.
>>>>>
>>>>>                           regards, tom lane
>>>>
>>>> The use case is for logging to syslog.
>>>>
>>>> Using the syslog_ident effectively changes the "program name" to
>>>> something
>>>> other than postgres. This would break any type of SIEM system that would
>>>> be
>>>> looking for events from the program postgres. This means that if you want
>>>> to
>>>> have a cluster specific contextual identifier, it needs to be in the log
>>>> message content, which for the purposes of postgresql means placing it
>>>> into
>>>> the log_line_prefix.
>>>>
>>>> It could be hard coded as part of the log_line_prefix such as
>>>>
>>>> log_line_prefix = 'cluster-db1:%d:%u:%h '
>>>>
>>>> That would work, but that means that my cluster name needs to be in the
>>>> configuration file twice and that opens up the error scenario of not
>>>> making
>>>> them exactly the same.
>>>>
>>>> Allowing for the cluster_name to be referenced by an escape sequence
>>>> would
>>>> make manual and automated configuration management easier.
>>> What if log_destination is set to csvlog? The same cluster_name is
>>> output in every lines, and there is no way to disable it because
>>> something like csv_line_prefix has not been supported yet?
>>>
>>> Regards,
>>>
>> I would think that in the case of using a csvlog that you would configure
>> the log_line_prefix to not include the escape sequence of the cluster_name.
>> The administrator would tune all of the logging components to work together,
>> or am I missing something here?
> log_line_prefix is only for stderr and syslog, not for csvlog.
> It cannot control what to output in csvlog, for now.
>
> Regards,

In that case, my request for a new escape sequence for the log_line_prefix will have no impact on csvlog output because it would
only affect uses cases where log_line_prefix is used AND where the administrator has added the cluster name into the log_line_prefix.

-- 
Evan


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