Scylla, datastax-java-driver integration problem

0
votes

I have three nodes Syclla cluster. I have keyspace which has 3 replication factor. I use datastax-java-driver 3.6.0 version and Scylla 3.0.0 version. When I tried to read my data with consistency level = LOCAL_QUORUM, I get error message below which is impossible in my opinion. As far as If I use LOCAL_QUORUM 2 nodes is enough for 3 replication factor.

Is it bug or am I missing something?

com.datastax.driver.core.exceptions.ReadTimeoutException: Cassandra timeout during read query at consistency LOCAL_QUORUM (3 responses were required but only 2 replica responded) com.datastax.driver.core.exceptions.ReadTimeoutException: Cassandra timeout during read query at consistency LOCAL_QUORUM (3 responses were required but only 2 replica responded) com.datastax.driver.core.exceptions.ReadTimeoutException: Cassandra timeout during read query at consistency LOCAL_QUORUM (3 responses were required but only 2 replica responded)

1
cassandradatastax-java-driverscylla
include the replication settings for your keyspace (the exact CREATE KEYSPACE line from schema best) - Chris Lohfink
@ChrisLohfink CREATE KEYSPACE logsourcev2 WITH replication = {'class': 'NetworkTopologyStrategy', 'dc1': '3'}. As I said I have 3 nodes test cluster. I have never seen 3 response were required message in my Cassandra cluster. It only happened in my Scylla cluster. - Yılmaz

1 Answers

3
votes

What happened here is that Scylla chose to do probabilistic read repair and detected mismatch before CL was reached. At this point it started to do repair between all three replicas and failed to read from all of them (either due to an overload or one node crashed/was restarted while operation was ongoing). You can disable probabilistic read repair to avoid it.