After upgrading from Telegraf 1.16.3 to 1.17.0, I've noticed that tags from statsd emissions are being mangled with unrelated metrics. I'm not pointing to this PR as the root cause for the regression, but this is also the only thing that's changed with the statsd plugin since the last release. If I have some more time I'll compile a more thorough bug report with a reproducible example.

Interesting. Thank you for reporting that, let me know when/if you get more info!

We've also seen the same mangled tags from statsd metrics after upgrading to 1.17.0

My golang is very rusty, but I think this is the cause of the issue:

The s.Lock() was moved from the start of parseStatsdLine to the start of aggregate. This means the lock has been moved from before tag calculation for a metric to after the tag calculation.

As the parser was recently multithreaded, this means there may be multiple goroutines calling the following line in parseStatsdLine which is now no longer inside a lock:

func (s *Statsd) parseName(bucket string) does not appear to be thread safe. First it pulls out tags for the current metric it was invoked with

then creates a GraphiteParser on the shared Statsd struct s

and sets the default tags on that shared GraphiteParser to the current metrics tags

this means multiple goroutines will be concurrently modifying s.graphiteParser.DefaultTags to different values and calling name, tags, field, _ = s.graphiteParser.ApplyTemplate(name) which will return incorrect tags if another goroutine has modified s.graphiteParser.DefaultTags