Some query context parameters cannot represented by string values

[anskarl]

When setting, for example, a priority parameter value in the query context as a string value (e.g., "1") like below:

val query: TimeSeriesQuery = DQL.timeseries
  .granularity(GranularityType.Hour)
  .interval("2011-06-01/2017-06-01")
  .agg(count as "count")
  .setQueryContextParam(QueryContext.Priority, "1")
  .build()

and in Druid we have query laning enabled, for example with the following settings:

#
# Query laning to test priorities
#
druid.query.scheduler.laning.strategy=hilo
druid.query.scheduler.laning.maxLowPercent=30
druid.query.default.context.lane=low
druid.query.scheduler.prioritization.strategy=manual

The resulting query (with some additional defaults (lane, and query id)) is the following:

{
   "queryType" : "timeseries",
   "granularity" : "HOUR",
   "intervals" : {
      "intervals" : [
         "2011-06-01T00:00:00.000Z/2017-06-01T00:00:00.000Z"
      ],
      "type" : "LegacySegmentSpec"
   },
   "postAggregations" : [],
   "aggregations" : [
      {
         "name" : "count",
         "type" : "count"
      }
   ],
   "limit" : 2147483647,
   "virtualColumns" : [],
   "dataSource" : {
      "name" : "wikipedia",
      "type" : "table"
   },
   "descending" : false,
   "context" : {
      "queryId" : "72afa724-fcac-498f-b5ef-31fe5da69175",
      "priority" : "1",
      "lane" : "low"
   }
}

You will get the following error: The future returned an exception of type: ing.wbaa.druid.client.HttpStatusException, with message: Received response with HTTP status code 500 Internal Server Error.

For more detailed view, in the broker logs you will get the corresponding error:

2021-05-24T06:54:21,145 WARN [qtp856880372-124[timeseries_[wikipedia]_72afa724-fcac-498f-b5ef-31fe5da69175]] org.apache.druid.server.QueryLifecycle - Exception while processing queryId [72afa724-fcac-498f-b5ef-31fe5da69175] (java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer)
2021-05-24T06:54:21,149 ERROR [qtp856880372-124[timeseries_[wikipedia]_72afa724-fcac-498f-b5ef-31fe5da69175]] org.apache.druid.server.QueryResource - Exception handling request: {class=org.apache.druid.server.QueryResource, exceptionType=class java.lang.ClassCastException, exceptionMessage=java.lang.String cannot be cast to java.lang.Integer, query={"queryType":"timeseries","dataSource":{"type":"table","name":"wikipedia"},"intervals":{"type":"LegacySegmentSpec","intervals":["2011-06-01T00:00:00.000Z/2017-06-01T00:00:00.000Z"]},"descending":false,"virtualColumns":[],"filter":null,"granularity":"HOUR","aggregations":[{"type":"count","name":"count"}],"postAggregations":[],"limit":2147483647,"context":{"lane":"low","priority":"-1","queryId":"72afa724-fcac-498f-b5ef-31fe5da69175"}}, peer=172.21.0.1} (java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer)

The error can be fixed by representing the priority value by an integer, for example:

{
   "queryType" : "timeseries",
   "granularity" : "HOUR",
   "intervals" : {
      "intervals" : [
         "2011-06-01T00:00:00.000Z/2017-06-01T00:00:00.000Z"
      ],
      "type" : "LegacySegmentSpec"
   },
   "postAggregations" : [],
   "aggregations" : [
      {
         "name" : "count",
         "type" : "count"
      }
   ],
   "limit" : 2147483647,
   "virtualColumns" : [],
   "dataSource" : {
      "name" : "wikipedia",
      "type" : "table"
   },
   "descending" : false,
   "context" : {
      "queryId": "5f5a1aa1-1e6a-4624-b90b-3acb04c179c5",
      "priority" : 1,
      "lane" : "low"
   }
}