When DD_AGENT_HOST is set to empty string, no data is sent, and there's no error

[jakub-g]

We've had an issue where after a backward incompatible change in GitLab 16.0 in how it populates variables, DD_AGENT_HOST variable suddenly became an empty string, and all places where hot-shots is used to send metrics from CI stopped sending metrics, although there were no errors in logs, and it took a while to understand why things have broken. Because by reading logs, everything looked "normal".

I managed to figure it out by reading this comment:

#197 (comment)

and logging the value of DD_AGENT_HOST in CI and seeing it's empty.

Relevant piece of code:

hot-shots/lib/statsd.js

Line 61 in b442244

this.host = options.host || process.env.DD_AGENT_HOST;

So it would be good to improve at least this particular aspect, but also in general the debugging is not always obvious, see #257