scripts/media-verify.py

@@ -9,8 +9,13 @@ its destination, and NO row may still name its source — a source row is a scan
 that has not caught up, and it is the one signature of a library pointing at
 files that no longer exist.
 
-Two doors, both read-only, both without a lock while the server runs
-(`mode=ro&immutable=1`; there is no `sqlite3` binary on these hosts):
+Two doors, both read-only, both without a lock while the server runs (there is
+no `sqlite3` binary on these hosts). Open `mode=ro` PLAIN: both servers keep
+their libraries in WAL mode, and `immutable=1` — which claims the file never
+changes — makes sqlite skip the write-ahead log entirely, so every row the
+server has committed but not yet checkpointed reads as MISSING, and a read
+beside a running scanner can even fail as "database disk image is malformed".
+`immutable=1` is only the fallback, for a database whose `-shm` cannot be read.
 
   jellyfin  `BaseItems.Path`. The container binds the share at `/data`, so the
             database holds `/data/<library>/…` where the journal holds
@@ -92,10 +97,18 @@ def read_moves(path):
 def server_paths(db, kind):
     """Every path the server holds, or a refusal that names what is missing."""
     spec = KINDS[kind]
-    try:
-        con = sqlite3.connect(f"file:{db}?mode=ro&immutable=1", uri=True)
-    except sqlite3.Error as e:
-        die(f"cannot open {db}: {e}")
+    con = None
+    err = None
+    # Plain ro reads the WAL the server commits through; immutable is the last
+    # resort, because it cannot see a row the server has not checkpointed.
+    for opt in ("mode=ro", "mode=ro&immutable=1"):
+        try:
+            con = sqlite3.connect(f"file:{db}?{opt}", uri=True)
+            break
+        except sqlite3.Error as e:
+            err = e
+    if con is None:
+        die(f"cannot open {db}: {err}")
     with con:
         have = {r[1] for r in con.execute(f"pragma table_info({spec['table']})")}
         if not spec["columns"] <= have:

tests/media_verify.bats

@@ -210,3 +210,38 @@ setup() {
     [ "${lines[3]}" = "missing from the DB: 0" ]
     [ "${lines[4]}" = "not indexed (extension ignored): 1" ]
 }
+
+# wal_case <db> — a Jellyfin database whose NEW row lives only in the
+# write-ahead log: the server has committed the rename but not checkpointed it,
+# which is the normal state of a library a scan is writing. The holder
+# connection keeps the WAL from folding into the main file, and the verifier
+# runs as a real subprocess so it faces the same files Plex and Jellyfin leave.
+wal_case() {
+    python3 - "$JFDB" "$JOURNAL" "$SHARE" "$VERIFY" <<'PY'
+import sqlite3, subprocess, sys
+db, journal, share, verify = sys.argv[1:5]
+w = sqlite3.connect(db)
+w.execute("pragma journal_mode=wal")
+w.execute("pragma wal_autocheckpoint=0")
+w.execute("insert into BaseItems (Path, Type) values ('/data/Movies/Old.mkv', 'x')")
+w.commit()
+w.execute("pragma wal_checkpoint(truncate)")
+holder = sqlite3.connect(db)  # last-connection close would checkpoint
+w.execute("update BaseItems set Path='/data/Movies/Old/Old.mkv'")
+w.commit()
+r = subprocess.run([sys.executable, verify, "--journal", journal,
+                    "--db-kind", "jellyfin", "--db", db,
+                    "--share", share, "--container", "/data"],
+                   capture_output=True, text=True)
+print(r.stdout, end="")
+sys.exit(r.returncode)
+PY
+}
+
+@test "a row the server committed but has not checkpointed is proof, not a miss" {
+    move_row "$SHARE/Movies/Old.mkv" "$SHARE/Movies/Old/Old.mkv"
+    run wal_case
+    [ "$status" -eq 0 ]
+    [ "${lines[1]}" = "landed: 1" ]
+    [ "${lines[3]}" = "missing from the DB: 0" ]
+}