Multiple Broker with Looker not working

Hi,

I have druid cluster with multiple brokers behind the AWS ALB with sticky session enabled. I am connecting the broker through Looker. When I have single broker all the queries works fine. When I add additional broker then randomly some queries work and some don’t. From Looker I get

Cannot run simple select query[simple SELECT query tests] Java::OrgApacheCalciteAvatica::AvaticaClientRuntimeException: Remote driver error: ISE: Connection[8b4d9fb4-2383-4aac-92e0-e2b5231aa0e1] already open

Can someone tell me what’s going on? Thanks

My broker configuration is as below

HTTP server threads

druid.server.http.numThreads=50

druid.server.http.maxIdleTime=PT5m

druid.server.http.defaultQueryTimeout=300000

druid.broker.http.numConnections=20

druid.broker.http.readTimeout=PT15M

druid.broker.http.unusedConnectionTimeout=PT4M

druid.broker.http.compressionCodec=gzip

Processing threads and buffers

druid.processing.buffer.sizeBytes=2147483647

druid.processing.numThreads=21

druid.sql.enable=true

#druid.sql.planner.useApproximateCountDistinct=false

druid.sql.http.enable=true

druid.sql.avatica.maxConnections=100

druid.sql.avatica.maxStatementsPerConnection=5

druid.sql.planner.maxQueryCount=50

druid.processing.numMergeBuffers=10

druid.query.groupBy.defaultStrategy=v2

druid.query.groupBy.maxMergingDictionarySize=1000000000

druid.query.groupBy.maxOnDiskStorage=2000000000

I wanted
the narrow the problem. I created a sample java project using “avatica” library
to connect to Druid. With single node it was working fine. When I added another
node it gave me the same exception as in looker. That confirmed that it is not
issue with Looker. After some investigation I found that the issue was due to
incorrect type of load balancer which I was using. I changed the load balancer
type from ALB to NLB and that solved the issue. I tested the setup via Looker
as well. Looker is able to connect to Druid having multiple broker nodes.

Hi Mohanraj,

Thanks for sharing with the community how you solved the issue. It will definitely help others in the future!

-Robert