Quota class final

Quota configuration helps to achieve fairness and budgeting in service usage.

The metric based quota configuration works this way:

• The service configuration defines a set of metrics.
• For API calls, the quota.metric_rules maps methods to metrics with corresponding costs.
• The quota.limits defines limits on the metrics, which will be used for quota checks at runtime.

An example quota configuration in yaml format:

quota: limits:

 - name: apiWriteQpsPerProject
   metric: library.googleapis.com/write_calls
   unit: "1/min/{project}"  # rate limit for consumer projects
   values:
     STANDARD: 10000


 (The metric rules bind all methods to the read_calls metric,
  except for the UpdateBook and DeleteBook methods. These two methods
  are mapped to the write_calls metric, with the UpdateBook method
  consuming at twice rate as the DeleteBook method.)
 metric_rules:
 - selector: "*"
   metric_costs:
     library.googleapis.com/read_calls: 1
 - selector: google.example.library.v1.LibraryService.UpdateBook
   metric_costs:
     library.googleapis.com/write_calls: 2
 - selector: google.example.library.v1.LibraryService.DeleteBook
   metric_costs:
     library.googleapis.com/write_calls: 1

Corresponding Metric definition:

 metrics:
 - name: library.googleapis.com/read_calls
   display_name: Read requests
   metric_kind: DELTA
   value_type: INT64

 - name: library.googleapis.com/write_calls
   display_name: Write requests
   metric_kind: DELTA
   value_type: INT64