qan-api2 inserts all CollectRequest's MetricsBucket in a single batch. That's better than store each bucket individually, but not good enough when there are 10-20 pmm-agents reporting data in the same moment as it effectively uses one ClickHouse connection per pmm-agent, consuming much memory.

DoD

• qan-api2 uses less ClickHouse connections, consumes less memory, and does not loose data.