In case you need to solve a streaming problem you might need to watch debug log. For that configure nginx with --with-debug flag.
$ cd nginx-X.Y.Z
$ ./configure --add-module=/path/to/nginx-rtmp-module --with-debug ...After compiling set nginx error.log level to debug in nginx.conf
error_log logs/error.log debug;After that you will have a lot of debug info in error.log. Please grep what your problem relates to (exec, notify etc) and post to nginx-rtmp google group to help with solving it.