Hi [email protected],
I wanted to invite feedback on a small logging feature I’m working on for
ATS by request from our ops team. ATS currently supports transactional
logging of specific header field values with expressions such as:
%<{x-primary-id}cqh>
`cqh` is the ATS log formatting field that prints the value of a particular
client request header field, in this case x-primary-id. Today, if that
header is not present, ATS logs the normal missing value, `-`. The proposed
feature allows a fallback chain so users can log an alternate header when
the primary one is absent.
Example:
%<{x-primary-id}cqh?:{x-secondary-id}cqh>
Note the `?:`, the proposed operator which signals the chain. This is
evaluated left to right:
- If x-primary-id exists, log that
- Otherwise if x-secondary-id exists, log that
- Otherwise log -
A few notes about the current behavior:
- This alternate chain feature is limited to header field log formats
for now (cqh, pqh, ssh, etc.).
- The chain can contain an arbitrary set of alternate field names (i.e.,
not just one alternate, but two, three, etc.).
- An existing header field with an empty value is treated as present.
Slices remain per-candidate, so this is valid:
%<{x-primary-id}cqh[0:8]?:{x-secondary-id}cqh[0:16]>
The goal is to make log configuration more flexible for deployments that
need to accommodate multiple header conventions for the same type of data
without duplicating formatting fields and requiring post-processing of
transaction logs.
For reference, here is a PR that implements this feature:
https://github.com/apache/trafficserver/pull/13018
Please let me know if you have feedback or concerns. If you have ideas
other than the `?:` operator, for instance, I'm definitely open to trying
something else.
Thanks!
Brian Neradt
--
"Come to Me, all who are weary and heavy-laden, and I will
give you rest. Take My yoke upon you and learn from Me, for
I am gentle and humble in heart, and you will find rest for
your souls. For My yoke is easy and My burden is light."
~ Matthew 11:28-30
