[openstack-dev] Log / error message format best practices & standards

Jay Pipes jaypipes at gmail.com
Thu Jun 26 18:54:58 UTC 2014

On 06/26/2014 12:14 PM, boden wrote:
> We were recently having a discussion over here in trove regarding a
> standardized format to use for log and error messages - obviously
> consistency is ideal (within and across projects). As this discussion
> involves the broader dev community, bringing this topic to the list for
> feedback...
> I'm aware of the logging standards wiki[1], however this page does not
> describe in depth a standardized format to use for log / error messages.
> In particular w/r/t program values in messages:
> (a) For in-line program values, I've seen both single quoted and
> unquoted formatting used. e.g.
> single quote: LOG.info("The ID '%s' is not invalid." % (resource.id))
> unquoted: LOG.info("The ID %s is not valid." % (resource.id))

No opinion on this one.

> (b) For program values appended to the message, I've seen various
> formats used. e.g.
> LOG.info("This path is invalid: %s" % (obj.path))
> LOG.info("This path is invalid %s" % (obj.path))
> LOG.info("This path is invalid - %s" % (obj.path))

The first would be my preference (i.e. using a ": " to delineate the 
target of the log message)

>  From a consistency perspective, it seems we should consider
> standardizing a best practice for such formatting.

Possibly, though this is likely getting into the realm of femto-nits and 

> For in-line values (#a above) I find single quotes the most consumable
> as they are a clear indication the value came from code and moreover
> provide a clear set of delimiters around the value. However to date
> unquoted appears to be the most widely used.
> For appended values (#b above) I find a delimiter such as ':' most
> consumable as it provides a clear boundary between the message and
> value. Using ':' seems fairly common today, but you'll find other
> formatting throughout the code.
> If we wanted to squash this topic the high level steps are (approximately):
> - Determine and document message format.
> - Ensure the format is part of the dev process (coding + review).
> - Cross team work to address existing messages not following the format.
> Thoughts / comments?
> [1] https://wiki.openstack.org/wiki/LoggingStandards
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