Transport

On a developer's laptop the ticketing server is a child process. The agent host starts python ticket_transport_server.py, writes one line of JSON to its standard input, and reads one line back from its standard output. In production the same code runs as three replicas behind the company's load balancer, and the same tools/call for get_ticket arrives as an HTTP POST that any of the three may answer. The previous three chapters treated the wire as if it did not matter. This one looks at it.