.

wcfs/__init__.py

@@ -20,7 +20,12 @@
 
 """Module wcfs.py provides python gateway for spawning and interoperating with wcfs server
 
-XXX doc
+Join(zurl) joins wcfs server. If wcfs server for zurl is not yet running, it
+can be automatically started if `autostart=True` parameter is passed to join.
+It will also be automatically started by default unless
+$WENDELIN_CORE_WCFS_AUTOSTART=no is specified in environment.
+
+XXX Conn.
 """
 
 import os, sys, hashlib, tempfile, subprocess, time
@@ -49,19 +54,19 @@ class Conn(object):
 
 # serve starts and runs wcfs server for ZODB @ zurl.
 #
-# it mounts wcfs at a location that is with 1-1 corresponence with zurl.
+# it mounts wcfs at a location that is with 1-1 correspondence with zurl.
 # it then waits for wcfs to exit (either due to unmount or an error).
 #
 # it is an error if wcfs was already started.
 #
-# if exec_ is True, wcfs is not spawned, but execed to.
+# if exec_ is True, wcfs is not spawned, but executed into.
 #
 # serve(zurl, exec_=False).
 def serve(zurl, exec_=False):
     mntpt = _mntpt_4zurl(zurl)
 
     # try opening .wcfs - it is an error if we can do it.
-    # XXX -> option to wcfs itself
+    # XXX -> option to wcfs itself?
     try:
         f = open(mntpt + "/.wcfs")
     except IOError as e:
@@ -80,14 +85,24 @@ def serve(zurl, exec_=False):
         os.execv(argv[0], argv)
 
 
+# _default_autostart returns default autostart setting for join.
+#
+# Out-of-the-box we want wcfs to be automatically started, to ease developer
+# experience when wendelin.core is standalone installed. However in environments
+# like SlapOS, it is more preferable to start and monitor wcfs service explicitly.
+# SlapOS & co. should thus set $WENDELIN_CORE_WCFS_AUTOSTART=no.
+def _default_autostart():
+    autostart = os.environ.get("WENDELIN_CORE_WCFS_AUTOSTART", "yes")
+    autostart = autostart.lower()
+    return {"yes": True, "no": False}[autostart]
+
 # join connects to wcfs server for ZODB @ zurl.
 #
-# if wcfs for that service was already started, join connects to it.
-# otherwise it starts wcfs for zurl if autostart is True or (None and system
-# default for autostart is True).   XXX
+# If wcfs for that service was already started, join connects to it.
+# Otherwise it starts wcfs for zurl if autostart is True.
 #
 # join(zurl) -> Conn.
-def join(zurl, autostart=None):
+def join(zurl, autostart=_default_autostart()):
     mntpt = _mntpt_4zurl(zurl)
 
     # try opening .wcfs - if we succeed - it is already mounted.
@@ -101,16 +116,18 @@ def join(zurl, autostart=None):
         # already have it
         return Conn(mntpt, f)
 
-    # XXX autostart=None processing
     if not autostart:
         raise RuntimeError("wcfs: join %s: server not started" % zurl)
 
-    return _start(zurl)
+    # start wcfs with telling it to automatically exit when there is no client activity.
+    return _start(zurl, "-autoexit")
 
 # _start starts wcfs server for ZODB @ zurl.
 #
-# _start(zurl) -> Conn
-def _start(zurl):
+# optv can be optionally given to pass flags to wcfs.
+#
+# _start(zurl, *optv) -> Conn
+def _start(zurl, *optv):
     mntpt = _mntpt_4zurl(zurl)
     log.info("wcfs: starting for %s ...", zurl)
 
@@ -123,7 +140,8 @@ def _start(zurl):
     def spawn():
         err = None
         try:
-            p = subprocess.Popen([_wcfs_exe(), zurl, mntpt], close_fds=True)
+            argv = [_wcfs_exe()] + list(optv) + [zurl, mntpt]
+            p = subprocess.Popen(argv, close_fds=True)
             while 1:
                 ret = p.poll()
                 if ret is not None:
@@ -140,7 +158,7 @@ def _start(zurl):
                     break
 
                 if _ == 1:
-                    # startup was ok - don't monitor spawned wcfs anylonger
+                    # startup was ok - don't monitor spawned wcfs any longer
                     break
 
                 time.sleep(0.1)
@@ -203,7 +221,13 @@ def _start(zurl):
 
     if _ == 1:
         if isinstance(_rx, file):
-            # mounted ok - return Conn object
+            # mounted ok - return Conn object.
+            #
+            # NOTE: we tell `spawn` thread to exit and stop monitoring spawned
+            # wcfs, because we want spawned wcfs to potentially overlive our
+            # process and to serve other processes. For the same reason we do
+            # not preserve cancel channel in returned Conn.
+
             f = _rx
             startedok.close()
             return Conn(mntpt, f)
@@ -212,7 +236,6 @@ def _start(zurl):
         err = _rx
 
 
-
     cancel.close()
     raise RuntimeError("wcfs: start: %s" % err) # XXX errctx
 

wcfs/todo.dot

@@ -3,9 +3,11 @@ digraph {
 	wcfs		-> ZODB_go_inv;
 	wcfs		-> Sinvtree;
 	wcfs		-> δR;
+	wcfs		-> autoexit;
 
 	wcfs_simple	-> Btree_read;
 	wcfs_simple	-> ZBlk_read;
+	wcfs_simple	-> autoexit;
 
 	client		-> wcfs_spawn;
 	client		-> δR;
@@ -27,4 +29,6 @@ digraph {
 
 	test		[label="? tests"]
 	zodburl		[label="zstor -> zurl", style=filled fillcolor=grey95]
+
+	autoexit	[label="autoexit if\nautostart && !activity"]
 }

wcfs/wcfs.go

@@ -119,7 +119,7 @@
 //	mmap(bigfile/<bigfileX>/head/data)
 //	mmap(bigfile/<bigfileX>/@<Cat>/data, δR(Cat,Sat), MAP_FIXED)  # mmaped at addresses corresponding to δR(Cat,Sat)
 //
-// When client completes its initiall mmapping it sends ack back to the server:
+// When client completes its initial mmapping it sends ack back to the server:
 //
 //	C: ack
 //
@@ -170,7 +170,7 @@
 // This way there should be no possibility for a client to block wcfs
 // indefinitely waiting for client's ack.
 //
-// Similarly for initiall mmapings client could first mmap head/data, then open
+// Similarly for initial mmapings client could first mmap head/data, then open
 // head/invalidations and tell the server that it wants Cat revision, with
 // the server then remmaping blocks to get to Cat state via ptrace.
 //
@@ -357,6 +357,8 @@ func (br *BigFileRoot) Mkdir(name string, mode uint32, _ *fuse.Context) (*nodefs
 	mkdir(br, name, bx) // XXX takes treeLock - ok under br.mu ?
 	mkdir(bx, "head", bf)
 	mkfile(bf, "data", bf.data)
+	// XXX mkfile(bf, "at", bf.at)
+	// XXX mkfile(bf, "invalidations", bf.inv)
 
 	return bx.Inode(), fuse.OK
 }
@@ -367,16 +369,15 @@ func (br *BigFileRoot) Mkdir(name string, mode uint32, _ *fuse.Context) (*nodefs
 
 
 // XXX option to prevent starting if wcfs was already started ?
-// XXX option to automatically exit/unmount if there are no requests for some t
-//     (UC: autospawned from join)
 
 func main() {
 	log.SetPrefix("wcfs: ")
 
 	debug := flag.Bool("d", false, "debug")
+	autoexit := flag.Bool("autoexit", false, "automatically stop service when there is no client activity")
 	flag.Parse()
 	if len(flag.Args()) != 2 {
-		log.Fatalf("Usage: %s zurl mntpt", os.Args[0])
+		log.Fatalf("Usage: %s [OPTIONS] zurl mntpt", os.Args[0])
 	}
 	zurl := flag.Args()[0]
 	mntpt := flag.Args()[1]
@@ -405,6 +406,9 @@ func main() {
 	mkfile(root, ".wcfs", NewStaticFile([]byte(zurl)))
 	mkdir(root, "bigfile", NewBigFileRoot(zstor))
 
+	// TODO handle autoexit
+	_ = autoexit
+
 	// serve client requests
-	server.Serve()	// XXX Serve returns no eror
+	server.Serve()	// XXX Serve returns no error
 }