Troubleshooting query execution in Druid

    1. The data servers don’t push any results to the Broker before the maximum idle time.
    1. 2021-09-14T19:52:27,685 ERROR [qtp475526834-85[scan_[test_large_table]_6eee73a6-a95f-4bdc-821d-981e99e39242]] org.apache.druid.server.QueryResource - Unable to send query response. (java.io.IOException: java.util.concurrent.TimeoutException: Idle timeout expired: 300000/300000 ms)
    • Increase the max idle time for the web server. Set the max idle time in the property in the historical/runtime.properties file. You must restart the Druid cluster for this change to take effect. See for more information on configuring the server.
    • If the timeout occurs because the data servers have not pushed any results to the Broker, consider optimizing data server performance. Significant slowdown in the data servers may be a result of spilling too much data to disk in groupBy v2 queries, large in the query, or an under scaled cluster. Analyze your Druid query metrics to determine the bottleneck.