Enhancements to support queue with AIMD and new metrics

[spericas]

Description

Enhancements to support queue with AIMD and new metrics. Issue #9542 and #9304.

Documentation

In a follow-up PR

[VishalSharma-123]

Hi @spericas.
While conducting the tests, I found out that the data for number of concurrent requests and for RTT Time was not being recorded properly. It remained at a constant value of 0.0 even under a load of very high user. Upon debugging the code, the invoke() method which contains the code for recording the data, was never called. Hence the data was not being recorded.

For it's fix, I tried to create a private class called FixedToken in FixedLimit.java, having a similar implementation as the AIMDToken in AIMDLimitImpl.java, and passing this class in the QueueSemaphore constructor for creating the handler. The required data for number of concurrent requests and for RTT Time is being recorded in FixedToken.

With this fix, the metric data for number of concurrent requests and for RTT Time is being recorded properly now.

Output Before the Fix
default_fixed_concurrent_requests{mp_scope="vendor",} 0.0 default_fixed_queue_wait_time_seconds{mp_scope="vendor",quantile="0.5",} 0.0 default_fixed_queue_wait_time_seconds{mp_scope="vendor",quantile="0.75",} 0.0 default_fixed_queue_wait_time_seconds{mp_scope="vendor",quantile="0.95",} 0.0 default_fixed_queue_wait_time_seconds{mp_scope="vendor",quantile="0.98",} 0.0 default_fixed_queue_wait_time_seconds{mp_scope="vendor",quantile="0.99",} 0.0 default_fixed_queue_wait_time_seconds{mp_scope="vendor",quantile="0.999",} 0.0 default_fixed_queue_wait_time_seconds_count{mp_scope="vendor",} 0.0 default_fixed_queue_wait_time_seconds_sum{mp_scope="vendor",} 0.0

Output After the Fix
default_fixed_concurrent_requests{mp_scope="vendor",} 51.0 default_fixed_queue_wait_time_seconds{mp_scope="vendor",quantile="0.5",} 0.452722688 default_fixed_queue_wait_time_seconds{mp_scope="vendor",quantile="0.75",} 0.704380928 default_fixed_queue_wait_time_seconds{mp_scope="vendor",quantile="0.95",} 1.140588544 default_fixed_queue_wait_time_seconds{mp_scope="vendor",quantile="0.98",} 1.409024 default_fixed_queue_wait_time_seconds{mp_scope="vendor",quantile="0.99",} 1.543241728 default_fixed_queue_wait_time_seconds{mp_scope="vendor",quantile="0.999",} 2.281439232 default_fixed_queue_wait_time_seconds_count{mp_scope="vendor",} 10547.0 default_fixed_queue_wait_time_seconds_sum{mp_scope="vendor",} 5652.533172794

I have also attached a zip that contains the new FixedLimit.java and a Difference.txt to highlight the changes.

Changes for Fixed Limit.zip