docker process hangs on write system call to stdout

Question

One application process inside a docker was not responding. When we strace'd the pid, process was stuck in the following line.

Strace Ouput:

root@hostname-blah ~ # strace -p 29353
strace: Process 29353 attached
write(1, "\n", 1

file descriptor 1 was pointing to /dev/pts/0

echo "abc" > /dev/pts/0

also got stuck in this affected docker container (but it was working in other containers).

Answer 1

This could be caused by this issue in Docker, that is specific to containers with allocated TTY: https://github.com/moby/moby/issues/35865