question: debugging access log format problems

[cmluciano]

Title: question: debugging access log format problems

Description:
The access log formatter does not appear to work without a null terminator \n . #87 was closed with an update to the docs noting the need for a newline separator. It makes sense to not enforce the newline when inserting a custom format, but a colleague and I found it difficult to determine that this may have been the problem since no leveled logging printed that there may be a problem.

I also tried validating with the config-checker tool , but it did not complain about the missing \n.

The JSON logger now automatically adds newlines with #5024 but the regular logger still can fail silently due to a bad format. Are there any potential logs or warnings that should catch these types of format problems, and if not would a PR to add some trace logs around this validation be accepted?

Repro steps:

1. Use curl get against an Envoy proxied web address with the custom access logger listed below and log-level set to trace.
2. Note that even with trace logging enabled, no warnings are printed and the access log is not displayed at all.

Config:

format: "[%START_TIME%] %PROTOCOL% %BYTES_RECEIVED% %BYTES_SENT% %RESPONSE_FLAGS% %UPSTREAM_HOST% %UPSTREAM_CLUSTER% %REQUESTED_SERVER_NAME%"

[stale]

This issue has been automatically marked as stale because it has not had activity in the last 30 days. It will be closed in the next 7 days unless it is tagged "help wanted" or other activity occurs. Thank you for your contributions.

[cmluciano]

@htuch @ggreenway looks like you both have merged things recently into the access log code.

Do either of you have any opinions on this?

[mattklein123]

@cmluciano can you propose a potential change here? From a quick read I'm not sure I fully grok the issue.

[ggreenway]

Is there any reasonable use-case for not having a newline in the format? I'd be fine with automatically adding a newline at the end if one isn't present.

[cmluciano]

@mattklein123 @ggreenway Yes the change I had in mind was validation that a newline is present and either logging or automatically adding one. Without the newline we don't see any error messages and access logging is non functional.

The change would be similar to #5024

[ggreenway]

That seems fine to me. If anyone comes up with a valid use-case for no-newline, you can put it behind a new config bit.

[htuch]

Automatically adding a new line if not present seems fine to me as well.

[cmluciano]

/assign @cmluciano

[stale]

This issue has been automatically marked as stale because it has not had activity in the last 30 days. It will be closed in the next 7 days unless it is tagged "help wanted" or other activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically closed because it has not had activity in the last 37 days. If this issue is still valid, please ping a maintainer and ask them to label it as "help wanted". Thank you for your contributions.