[GitHub] [incubator-doris] xinghuayu007 opened a new issue #4927: [Proposal] Backends need to set priority to mannually load balance

[GitBox <gi...@apache.org>]

xinghuayu007 opened a new issue #4927:
URL: https://github.com/apache/incubator-doris/issues/4927


   **Is your feature request related to a problem? Please describe.**
     In real maintenance of Doris, we found that sometimes one query is delayed seriously by only one node. We call it `Slow Node`. Maybe the hardware of a `Slow Node` is not good enough than other nodes, or it's load is high for a long time. It is necessary to mannual reduce more queries distributed to this `Slow Node`. Therefore, it is meaningful to give every backend a priority. When a `Slow Node` appears, we can set it's priority lower to reduce queries distributed to it.  
   
   **Describe the solution you'd like**
   1. Every backend has a priority [1-10], 1 is the lowest priority, 10 is the highest priority.
   
   2. When add a backend to the sytem, we can set it's priority. If it is not setted, the default priority is 10.
   
    `alter system add backend "host:port" properties("priority"="8")`
   
   3. We can set one backend's priority at any time
   
    `alter system modify backend "host:port" properties("priority"="9")`
   
   4. The priority is a globa variable, not a session variable.
   
   5. When plan a query, it likes to chose high priority host of replica
   
   **Describe alternatives you've considered**
   A clear and concise description of any alternative solutions or features you've considered.
   
   **Additional context**
   Add any other context or screenshots about the feature request here.
   


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