App engine endpoint warning

Question

When I check my logs on my GAE app, I can see every so often a warning message like that:

com.google.api.control.Client flushAndScheduleReports: direct send of a report request failed because of endpoints.repackaged.com.google.api.client.http.HttpResponseException: 400 (Client.java:354)
{
  "error": {
    "code": 400,
    "message": "Precondition check failed.",
    "errors": [
      {
        "message": "Precondition check failed.",
        "domain": "global",
        "reason": "failedPrecondition"
      }
    ],
    "status": "FAILED_PRECONDITION"
  }
}

However it seems the client app works as expected and I don't understand what it means.

Answer 1

If you have a low traffic API, this typically will happen if too long goes in between requests. The app will work as expected, but metric reporting may be off. This is because metrics are aggregated and reported every so many requests, unless you're running a backend instance.