support json serialization of Yielders
pass through errors from computes in DirectDruidClient
formatting
proper query exceptions and add support for query timeout
properly remove completed queries from query manager
return proper json errors to propagate query cancellation and timeout
make sure to close yielder when serializing json
add dummy watcher for tests
forward cancellation in direct druid client
less stack traces when cancelling queries
proper query cancellation tests
properly kill timed out queries
make sure to close yielder in MetricsEmittingQueryRunner
interrupt queries on incremental indexer
remove unused code