RethinkDB 2.4 broke my app's tests, which read RethinkDB's stdout stream to wait for the "Server ready" text before attempting to connect to it.

This is apparently caused by a change to how RethinkDB buffers its console output.

via @srh on Slack:

The difference can also be observed by running rethinkdb | cat on v2.3.x and v2.4.0.

A write system call got replaced with an fwrite at commit/line 6455c907672#diff-ecd09eaab98f8bf01f631c194cd5c675R475 . So it is performing buffered I/O to the console without flushing. A call to fflush(write_stream) fixes this and should be added.