X wcfs: Switch mountpoints from /tmp/wcfs/* to /dev/shm/*

This way multiple zopes, which all have their own separate $TMP and $TMPDIR,
can still access shared WCFS instance. And new place fits naturally into
general wendelin.core logic (see added comment).

wcfs/__init__.py

@@ -63,7 +63,7 @@ The following environment variables can be used to control wcfs.py client:
 
 from __future__ import print_function, absolute_import
 
-import os, sys, hashlib, tempfile, subprocess, time, stat
+import os, sys, hashlib, subprocess, time, stat
 import logging as log
 from os.path import dirname
 from errno import ENOENT, EEXIST
@@ -310,8 +310,12 @@ def _mntpt_4zurl(zurl):
     m = hashlib.sha1()
     m.update(zurl)
 
-    # mkdir /tmp/wcfs with stiky bit. This way multiple users can create subdirectories inside.
-    wcfsroot = "%s/wcfs" % (tempfile.gettempdir())
+    # WCFS mounts are located under /dev/shm/wcfs. /dev/shm is already used by
+    # userspace part of wendelin.core memory manager from multiple processes.
+    # In a sense WCFS mount provides shared read-only memory backed by ZODB.
+
+    # mkdir /dev/shm/wcfs with stiky bit. This way multiple users can create subdirectories inside.
+    wcfsroot = "/dev/shm/wcfs"
     wcfsmode = 0o777 | stat.S_ISVTX
     if _mkdir_p(wcfsroot):
         os.chmod(wcfsroot, wcfsmode)

[Kirill Smelkov]

/cc @rafael