CheckRequestAggregator produces many warnings #177

Hi,

I'm using the Endpoints framework with App Engine Standard Java 8. I have configured API control using the GoogleAppEngineControlFilter for the EndpointsServlet. This works fine; fine-grained metrics are pushed to the service control API and I can access these using the UI.

However, my App Engine log contains many of the following warnings:

com.google.api.control.aggregator.CheckRequestAggregator handleCachedResponse: latest check request has not completed (CheckRequestAggregator.java:257)

There are about 10 of these per hour, a bunch of few (3-5) occurs every 15 - 20 minutes. I'm running my app on a single App Engine instance with a constant load of 5 requests per second.