I wonder if my socket recv function is blocked on the other end, causing the socket send function to block in print_message function in babeltrace2;or when printing to the console, the printing speed can't keep up with the parsed CTF data generation speed and the print buffer is also full.

In this case, how will Babeltrace2 handle the parsed CTF data that has not been sent yet, store them in a buffer, a queue or just discard them? Or would the blocking directly cause LTTng to discard the original CTF data at the ring buffer before LTTng Consumer daemon?

Not sure I understand your setup but when using lttng-live, you are effectively reading from the data that lttng-relayd is collecting, piece by piece.

The producing side is not affected by the speed at which the reader (babeltrace2) consume data from lttng-relayd using the lttng-live protocol.

There might be some corner case here and there but for most base usage of the "live" feature reader (babeltrace2) and producer(lttng/lttng-consumerd)

are "decoupled". You can consider the "lttng-relayd" (and the trace on the filesystem) as the "buffer" here.