I stumbled upon an old but interesting blog post while searching for the cost of creating an App Engine instance (as part of a greater effort to most accurately associate Google Cloud Platform project costs with App Engine activity). Specifically, http://blog.initlabs.com/post/16359268329/how-i-reduced-google-app-engine-costs-by-75 espouses the use of Appstats, which "can keep track of RPC cost as well as time." (By the way, the Google Cloud article was updated August 25, 2017 and doesn't contain terms like "deprecated", "replaced", "Trace", or "Stackdriver", which makes me think Appstats may still provide value.) Three questions on this note:
As per Alex Martelli's StackOverflow answer in early 2015, 'Cloud Trace is in beta, meaning "it's not covered by any SLA or deprecation policy and may be subject to backward-incompatible changes", while AppStats is a supported component of App Engine.' While it seems Trace graduated from beta, I also don't see any deprecation notices for Appstats. Alex continues, "Since AppStats is a supported component, it is subject to the usual deprecation policy, and thus it will be around for a minimum of one year after it's officially announced as deprecated (if such an announcement ever happens), so there is really no urgency for you to consider migrating production apps off it at this time." However, in his comment below, "[Cloud Trace is not announced as a replacement for AppStats], but it is, quite understandably, how many people are perceiving it:-)." Can anybody verify that Appstats is still supported?
There are a couple of deprecated methods listed in https://cloud.google.com/appengine/docs/standard/python/refdocs/google.appengine.ext.appstats.recording, but cost information is not. Is there reason to believe Appstats's cost information is meaningful while Stackdriver's is not, or does the documentation need to be revised (it was last updated August 28, 2017, though)?
What are the limitations of using Appstats? I see that only Java 7 Runtime is supported (https://cloud.google.com/appengine/docs/standard/java/tools/appstats). I also can't find documentation for Appstats on App Engine flexible environment; does it necessitate use of standard? The latter is a bigger deal to me.
If you'd like more details as to why I'm looking into this and what I've already explored (especially with regards to information provided by Stackdriver and billing export to BigQuery), please take a look at How can I most accurately associate Google Cloud Platform project costs with App Engine activity?