3.x|4.x: LWT Statements routing decision is ignoring lb policy

[dkropachev]

Both 3.x and 4.x ignore LoadBalancingPolicy and return all the replicas in the same order they get it from vnodes or tablets for LWT statements and it seems wrong to me:

• Java 3.x

  java-driver/driver-core/src/main/java/com/datastax/driver/core/RequestHandler.java

  Lines 144 to 159 in 31a7a72

  	if (statement.getHost() != null) {
  	this.queryPlan = new QueryPlan(Iterators.singletonIterator(statement.getHost()));
  	} else if (statement.isLWT()) {
  	this.queryPlan =
  	new QueryPlan(
  	getReplicas(
  	manager.poolsState.keyspace,
  	statement,
  	manager
  	.loadBalancingPolicy()
  	.newQueryPlan(manager.poolsState.keyspace, statement)));
  	} else {
  	this.queryPlan =
  	new QueryPlan(
  	manager.loadBalancingPolicy().newQueryPlan(manager.poolsState.keyspace, statement));
  	}

• Java 4.x

  java-driver/core/src/main/java/com/datastax/oss/driver/internal/core/cql/CqlRequestHandler.java

  Lines 208 to 226 in 4ba0657

  	if (this.initialStatement.getNode() != null) {
  	queryPlan = new SimpleQueryPlan(this.initialStatement.getNode());
  	} else if (this.initialStatement.isLWT()) {
  	queryPlan =
  	getReplicas(
  	session.getKeyspace().orElse(null),
  	this.initialStatement,
  	context
  	.getLoadBalancingPolicyWrapper()
  	.newQueryPlan(initialStatement, executionProfile.getName(), session));
  	} else {
  	queryPlan =
  	context
  	.getLoadBalancingPolicyWrapper()
  	.newQueryPlan(initialStatement, executionProfile.getName(), session);
  	}
  	sendRequest(initialStatement, null, queryPlan, 0, 0, true);
  	}

As result there is no way to make them target rack or dc, even more than that, when user feeds RackAwareRoundRobinPolicy to cluster config LWT queries are getting routed, unexpectedly, to all racks.