Sending kafka broker logs to mysql database

I have been working on storing apache-kafka broker logs into mysql database. Kafka has log4j jar file which has JDBC appender through that we can store logs directly into database. So I found file in kafka and tried to add JDBC properties lines in properties so it can send logs to database along with console and log file which is default logging feature in kafka

How to control the concurrency of processing messages by ConsumerGroup

I am using kafka-node ConsumerGroup to consume message from a topic. The ConsumerGroup when consumes a message requires calling an external API, which might even take a second to response.
I wish to control consuming next message from the queue until I get the response from the API, so that the messages are processed sequentially.