error while parsing $upstream_response_time: value '-' could not be parsed into float

[lhanjian]

Describe the bug

error while parsing $upstream_response_time: value '-' could not be parsed into float

Root cause(?)

https://github.com/martin-helmich/prometheus-nginxlog-exporter/pull/221/files#diff-2873f79a86c0d8b3335cd7731b0ecf7dd4301eb19a82ef7a1cba7589b5252261R453

[lhanjian]

$upstream_response_time either a number or unset. Nginx logs unset variables as dash (-)

https://stackoverflow.com/questions/36788856/nginx-log-filter-upstream-response-time-json-elk-parsefailure

[lhanjian]

it may be "502, -, 502" or "-"

[martin-helmich]

Yes, this was introduced as a side effect of #221 -- this should not affect metrics generation, since the error is only logged (meaning the actual metrics should be provided just the same as before). However, I do get that the logs are annoying and should not increase the parse_error_count metric. Will fix shortly.