multi resource contorl client not in balance

[nolouch]

What did you do?

alter resource group rg2 RU_PER_SEC=6000;
sysbench --mysql-host=127.0.0.1 --mysql-user=user2 --mysql-port=4000 --mysql-db=sbtest --percentile=99 --report-interval=1 --tables=32 --table_size=10000000 oltp_read_only --range_selects --threads=128 --time=1800 run

and QPS not balanced in client side

What did you expect to see?

the client's qps is balanced.

What did you see instead?

What version of PD are you using (pd-server -V)?

master

[nolouch]

cc @JmPotato could you help to take a look at this issue?

[JmPotato]

This is because we don't have a mechanism to balance the different client RU-acquiring counts within the same resource group. To solve it, we need to implement a way to pre-allocate and adjust the RU quota dynamically for different clients to achieve an even or weighted QPS.

[JmPotato]

After some investigation, an initial idea is to divide the token bucket into N sub-buckets evenly according to the current client connection number within the same resource group. And each sub-bucket could seize other sub-buckets' tokens if its own could not meet the requirement and the other one has enough balance. By this approach, we could:

• Obtain an even QPS when a resource group has multiple clients asking for tokens overwhelmingly.
• No waste on the unused tokens if some of the clients are not that busy.

What do you guys think? @nolouch @glorv @HuSharp @CabinfeverB

[CabinfeverB]

I couldn't agree with you more on the general idea. But I think it should attempt over a period of time or multiple times firstly to get permission for seizing other sub-buckets' tokens . We can assume that in the case of two clinet, both clients have no load at the beginning and there is a certain token. However, if the load of two clients rises suddenly and client1's request arrives at the server first, ithe server may assign all tokens directly to client1.