OSError: AF_UNIX path length cannot exceed 103 bytes

The error

OSError: AF_UNIX path length cannot exceed 103 bytes: 
'/var/folders/qj/147cfvxs1xq6bp88xdcd4vt80000gq/T/outflow_ray_tp65lllr/
session_2021-05-05_16-16-18_112187_70483/sockets/plasma_store'

is raised when using the backend: ray.

Ray needs to create a temporary folder. The path of this folder is composed of

• a part created by tempfile.mkdtemp(prefix="outflow_ray_") : /var/folders/qj/147cfvxs1xq6bp88xdcd4vt80000gq/T/outflow_ray_b2f2h7js
• a part created with strftime in ray/node.py : session_2021-05-05_16-16-18_112187_70483

Both are long, and there is a system limitation of 104 bytes for sockets names See https://github.com/ray-project/ray/issues/7724 where the problem is described

A workaround is to set en environment variable TMPDIR, TEMP or TMP to /tmp/ (see https://docs.python.org/3/library/tempfile.html#tempfile.mkstemp). tempfile.mkdtemp will return a much shorter temporary file name.