Add helper script to benchmark rate limiting

This script needs to be piped into bin/console on the api vm.

scripts/benchmark_rate_limiting.rb

@@ -0,0 +1,45 @@
+# usage: pipe this script into bin/console on the api vm
+# this script logs to stderr, thus you might want to redirect stdout to /dev/null
+
+NUM_USERS = 1000
+NUM_REQUESTS_PER_USER = 1000
+
+logger = Logger.new($stderr)
+
+rate_limiter = CloudFoundry::Middleware::RateLimiter::EXPIRING_REQUEST_COUNTER
+rate_limiter_v2 = CloudFoundry::Middleware::RateLimiterV2API::EXPIRING_REQUEST_COUNTER
+service_broker_rate_limiter = CloudFoundry::Middleware::ServiceBrokerRateLimiter::CONCURRENT_REQUEST_COUNTER
+reset_interval_in_minutes = 60
+max_concurrent_requests = 10
+
+logger.info("Creating #{NUM_USERS} random user guids...")
+user_guids = []
+NUM_USERS.times do
+  user_guids << SecureRandom.uuid
+end
+logger.info('    ... done.')
+
+logger.info('Running benchmark...')
+result = Benchmark.measure do
+  NUM_REQUESTS_PER_USER.times do |i|
+    user_guids.each do |user_guid|
+      rate_limiter.increment(user_guid, reset_interval_in_minutes, logger)
+      rate_limiter_v2.increment(user_guid, reset_interval_in_minutes, logger)
+      service_broker_rate_limiter.try_increment?(user_guid, max_concurrent_requests, logger)
+      service_broker_rate_limiter.decrement(user_guid, logger)
+    end
+
+    completion_percentage = i.to_f / NUM_REQUESTS_PER_USER * 100
+    if completion_percentage % 10 == 0
+      logger.info("    (#{completion_percentage.to_i}% completed)")
+    end
+  end
+end
+logger.info('    ... done.')
+
+num_rate_limit_events = 4 * NUM_USERS * NUM_REQUESTS_PER_USER
+logger.info('Results:')
+logger.info("    User CPU time     =  #{format("%.1f", result.utime)}s  (per rate limit event: #{format("%.3f", result.utime / num_rate_limit_events * 1000)}ms)")
+logger.info("    System CPU time   =  #{format("%.1f", result.stime)}s  (per rate limit event: #{format("%.3f", result.stime / num_rate_limit_events * 1000)}ms)")
+logger.info("    Total time        =  #{format("%.1f", result.total)}s  (per rate limit event: #{format("%.3f", result.total / num_rate_limit_events * 1000)}ms)")
+logger.info("    Elapsed real time =  #{format("%.1f", result.real)}s  (per rate limit event: #{format("%.3f", result.real / num_rate_limit_events * 1000)}ms)")