kaisun2000 opened a new pull request, #15176:
URL: https://github.com/apache/druid/pull/15176

   
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   ### Description
   
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   Currently the inter Druid communication via rest endpoints is based on json 
formatted payload. Upon parsing error, there is only a generic exception 
stating expected json token type and current json token type. There is no 
detailed error log about the content of the payload causing the violation. 
   
   In the micro-service world, the trend is to deploy the Druid servers in k8 
with the mesh network. Often the istio proxy or other proxies is used to 
intercept the network connection between Druid servers. The proxy may give 
error messages for various reasons. These error messages are not expected by 
the json parser. The generic error message from Druid can be very misleading as 
the user may think the message is based on the response from the other Druid 
server. 
   
   For example, this is an example of mysterious error message
   
   ```
   QueryInterruptedException{msg=Next token wasn't a START_ARRAY, 
was[VALUE_STRING] from url[http://xxxxx:8088/druid/v2/], code=Unknown 
exception, class=org.apache.druid.java.util.common.IAE, host=xxxxx:8088}"
   ```
   
   While the context of the message is the following from the proxy when it 
can't tunnel the network connection.
   
   ```
   pstream connect error or disconnect/reset before header
   ```
   
   So this very simple PR is just to enhance the logging and get the real 
underlying message printed out. This would save a lot of head scratching time 
if Druid is deployed with mesh network. 
   
   
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   <hr>
   Improved: enhanced the json parser unexpected token logging with the context 
of the expected VALUE_STRING token. This way, it is easier to track to 
mesh/proxy network error messages, instead misleading user to track the Druid 
server rest endpoint responses.
   <hr>
   
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   This PR has:
   
   - [x] been self-reviewed.
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   - [ ] added integration tests.
   - [x] been tested in a test Druid cluster.
   


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