add landmarks (#182)

README.md

@@ -1605,7 +1605,7 @@ config file example:
     w: *    # anyone can upload here
     rw: ed  # only user "ed" can read-write
   flags:
-    e2ds:      # filesystem indexing is required for many of these:
+    e2ds       # filesystem indexing is required for many of these:
     sz: 1k-3m  # accept upload only if filesize in this range
     df: 4g     # free disk space cannot go lower than this
     vmaxb: 1g  # volume can never exceed 1 GiB
@@ -1662,6 +1662,8 @@ this can instead be kept in a single place using the `--hist` argument, or the `
 
 by default, the per-volume `up2k.db` sqlite3-database for `-e2d` and `-e2t` is stored next to the thumbnails according to the `--hist` option, but the global-option `--dbpath` and/or volflag `dbpath` can be used to put the database somewhere else
 
+if your storage backend is unreliable (NFS or bad HDDs), you can specify one or more "landmarks" to look for before doing anything database-related. A landmark is a file which is always expected to exist inside the volume. This avoids spurious filesystem rescans in the event of an outage. One line per landmark (see example below)
+
 note:
 * putting the hist-folders on an SSD is strongly recommended for performance
 * markdown edits are always stored in a local `.hist` subdirectory
@@ -1679,6 +1681,8 @@ config file example:
   flags:
     hist: -  # restore the default (/mnt/nas/pics/.hist/)
     hist: /mnt/nas/cache/pics/  # can be absolute path
+    landmark: me.jpg  # /mnt/nas/pics/me.jpg must be readable to enable db
+    landmark: info/a.txt^=ok  # and this textfile must start with "ok"
 ```
 
 

copyparty/authsrv.py

@@ -386,20 +386,20 @@ class VFS(object):
         self.adot: dict[str, list[str]] = {}
         self.js_ls = {}
         self.js_htm = ""
+        self.all_vols: dict[str, VFS] = {}  # flattened recursive
+        self.all_nodes: dict[str, VFS] = {}  # also jumpvols/shares
 
         if realpath:
             rp = realpath + ("" if realpath.endswith(os.sep) else os.sep)
             vp = vpath + ("/" if vpath else "")
             self.histpath = os.path.join(realpath, ".hist")  # db / thumbcache
             self.dbpath = self.histpath
-            self.all_vols = {vpath: self}  # flattened recursive
-            self.all_nodes = {vpath: self}  # also jumpvols/shares
+            self.all_vols[vpath] = self
+            self.all_nodes[vpath] = self
             self.all_aps = [(rp, [self])]
             self.all_vps = [(vp, self)]
         else:
             self.histpath = self.dbpath = ""
-            self.all_vols = {}
-            self.all_nodes = {}
             self.all_aps = []
             self.all_vps = []
 
@@ -868,6 +868,53 @@ class VFS(object):
 
         return self
 
+    def check_landmarks(self) -> bool:
+        if self.dbv:
+            return True
+
+        vps = self.flags.get("landmark") or []
+        if not vps:
+            return True
+
+        failed = ""
+        for vp in vps:
+            if "^=" in vp:
+                vp, zs = vp.split("^=", 1)
+                expect = zs.encode("utf-8")
+            else:
+                expect = b""
+
+            if self.log:
+                t = "checking [/%s] landmark [%s]"
+                self.log("vfs", t % (self.vpath, vp), 6)
+
+            ap = "?"
+            try:
+                ap = self.canonical(vp)
+                with open(ap, "rb") as f:
+                    buf = f.read(4096)
+                    if not buf.startswith(expect):
+                        t = "file [%s] does not start with the expected bytes %s"
+                        failed = t % (ap, expect)
+                        break
+            except Exception as ex:
+                t = "%r while trying to read [%s] => [%s]"
+                failed = t % (ex, vp, ap)
+                break
+
+        if not failed:
+            return True
+
+        if self.log:
+            t = "WARNING: landmark verification failed; %s; will now disable up2k database for volume [/%s]"
+            self.log("vfs", t % (failed, self.vpath), 3)
+
+        for rm in "e2d e2t e2v".split():
+            self.flags = {k: v for k, v in self.flags.items() if not k.startswith(rm)}
+        self.flags["d2d"] = True
+        self.flags["d2t"] = True
+        return False
+
 
 if WINDOWS:
     re_vol = re.compile(r"^([a-zA-Z]:[\\/][^:]*|[^:]*):([^:]*):(.*)$")
@@ -1501,7 +1548,7 @@ class AuthSrv(object):
             flags[name] = True
             return
 
-        zs = "ext_th mtp on403 on404 xbu xau xiu xbc xac xbr xar xbd xad xm xban"
+        zs = "ext_th landmark mtp on403 on404 xbu xau xiu xbc xac xbr xar xbd xad xm xban"
         if name not in zs.split():
             if value is True:
                 t = "└─add volflag [{}] = {}  ({})"
@@ -2237,6 +2284,8 @@ class AuthSrv(object):
                 t = "WARNING: volume [/%s]: invalid value specified for ext-th: %s"
                 self.log(t % (vol.vpath, etv), 3)
 
+            vol.check_landmarks()
+
             # d2d drops all database features for a volume
             for grp, rm in [["d2d", "e2d"], ["d2t", "e2t"], ["d2d", "e2v"]]:
                 if not vol.flags.get(grp, False):

copyparty/cfg.py

@@ -222,6 +222,7 @@ flagcats = {
         "d2d": "disables all database stuff, overrides -e2*",
         "hist=/tmp/cdb": "puts thumbnails and indexes at that location",
         "dbpath=/tmp/cdb": "puts indexes at that location",
+        "landmark=foo": "disable db if file foo doesn't exist",
         "scan=60": "scan for new files every 60sec, same as --re-maxage",
         "nohash=\\.iso$": "skips hashing file contents if path matches *.iso",
         "noidx=\\.iso$": "fully ignores the contents at paths matching *.iso",

copyparty/up2k.py

@@ -1379,6 +1379,10 @@ class Up2k(object):
                     t = "volume /%s at [%s] is empty; will not be indexed as this could be due to an offline filesystem"
                     self.log(t % (vol.vpath, rtop), 6)
                     return True, False
+                if not vol.check_landmarks():
+                    t = "volume /%s at [%s] will not be indexed due to bad landmarks"
+                    self.log(t % (vol.vpath, rtop), 6)
+                    return True, False
 
                 n_add, _, _ = self._build_dir(
                     db,