[GitHub] [spark] LuciferYang commented on pull request #37999: [SPARK-39146][CORE][SQL][K8S] Introduce `JacksonUtils` to use singleton Jackson ObjectMapper

Mon, 26 Sep 2022 23:19:25 -0700 


LuciferYang commented on PR #37999:
URL: https://github.com/apache/spark/pull/37999#issuecomment-1259031253

   @srowen From the above test results, there is no significant performance 
difference between using global and local singletons.
   
   From a code perspective, thread safety should not be guaranteed by locks, it 
seems guaranteed by using a new `JsonParser/JsonGenerator` every serialization 
and deserialization.
   
   
https://github.com/FasterXML/jackson-databind/blob/492334da383b0677c19b08964fddad18230546af/src/main/java/com/fasterxml/jackson/databind/ObjectMapper.java#L3838-L3851
   
   <img width="949" alt="image" 
src="https://user-images.githubusercontent.com/1475305/192445439-80fc6740-767f-4848-b444-f6c22a40d1cc.png";>
   
   
https://github.com/FasterXML/jackson-databind/blob/492334da383b0677c19b08964fddad18230546af/src/main/java/com/fasterxml/jackson/databind/ObjectMapper.java#L3647-L3658
   
   <img width="885" alt="image" 
src="https://user-images.githubusercontent.com/1475305/192445680-6c2065ff-7cf4-4d60-8c01-df219eb629ab.png";>
   
   So there seems to be no problem with the global instance. `ObjectMapper` is 
only used as a configuration template, so I am both ok to use a global 
singleton or local singleton
   
   
   
   
   
   


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