Honor configurable cache size with LRU eviction

README.md

@@ -67,6 +67,19 @@ The fixed source blacklist is:
 
 Client error reports never modify this list.
 
+## Cache resizing
+
+`CACHE_MAX_BYTES` is the worker's configurable LRU limit. After changing it and
+restarting the container:
+
+- A smaller value evicts the oldest unlocked entries until usage fits.
+- A larger value immediately makes the additional capacity available for
+  background population, up to the size of the mounted cache filesystem.
+
+The host filesystem is deliberately separate from application logic. Enlarge or
+shrink its preallocated image during infrastructure maintenance, then set the
+matching `CACHE_MAX_BYTES` value in Coolify.
+
 ## Playback locking
 
 - An active movie locks that movie.

pretranscode.py

@@ -31,6 +31,7 @@ JELLYFIN_LIBRARY_ROOT = os.environ.get("JELLYFIN_LIBRARY_ROOT", "/data/library")
 JELLYFIN_ORIGINAL_ROOT = os.environ.get("JELLYFIN_ORIGINAL_ROOT", "/data/original").rstrip("/")
 JELLYFIN_CACHE_ROOT = os.environ.get("JELLYFIN_CACHE_ROOT", "/data/cache").rstrip("/")
 JELLYFIN_API_KEY = os.environ.get("JELLYFIN_API_KEY", "")
+CACHE_MAX_BYTES = env_int("CACHE_MAX_BYTES", 1_000_000_000_000)
 SERIES_COOLDOWN_SECONDS = env_int("SERIES_COOLDOWN_SECONDS", 3600)
 POLL_SECONDS = env_int("POLL_SECONDS", 5)
 RESCAN_SECONDS = env_int("RESCAN_SECONDS", 300)
@@ -501,9 +502,33 @@ class Manager:
         manifest.unlink(missing_ok=True)
         return True
 
+    def cache_usage(self):
+        return sum(
+            path.stat().st_size
+            for path in (CACHE_ROOT / "files").iterdir()
+            if path.is_file()
+        )
+
+    def cache_available(self):
+        stat = os.statvfs(CACHE_ROOT)
+        filesystem_free = stat.f_bavail * stat.f_frsize
+        configured_free = max(0, CACHE_MAX_BYTES - self.cache_usage())
+        return min(filesystem_free, configured_free)
+
+    def enforce_cache_limit(self):
+        usage = self.cache_usage()
+        for _, relative, output, manifest in self.cache_entries():
+            if usage <= CACHE_MAX_BYTES:
+                break
+            if self.is_locked(relative):
+                continue
+            size = output.stat().st_size + manifest.stat().st_size
+            log(f"Evicting {relative} after cache resize")
+            if self.remove_cache(relative):
+                usage -= size
+
     def ensure_space(self, required, may_evict):
-        free = os.statvfs(CACHE_ROOT).f_bavail * os.statvfs(CACHE_ROOT).f_frsize
-        if free >= required:
+        if self.cache_available() >= required:
             return True
         if not may_evict:
             return False
@@ -512,8 +537,7 @@ class Manager:
                 continue
             log(f"Evicting {relative}")
             self.remove_cache(relative)
-            free = os.statvfs(CACHE_ROOT).f_bavail * os.statvfs(CACHE_ROOT).f_frsize
-            if free >= required:
+            if self.cache_available() >= required:
                 return True
         return False
 
@@ -625,6 +649,7 @@ class Manager:
         if not JELLYFIN_API_KEY:
             raise RuntimeError("JELLYFIN_API_KEY is required")
         self.read_sessions()
+        self.enforce_cache_limit()
         self.scan_inventory()
         self.sync_view()
         self.save()
@@ -632,6 +657,7 @@ class Manager:
             if not self.read_sessions():
                 time.sleep(POLL_SECONDS)
                 continue
+            self.enforce_cache_limit()
             now = time.time()
             if now - self.last_scan >= RESCAN_SECONDS:
                 changed = self.scan_inventory()
@@ -651,8 +677,7 @@ class Manager:
             for rank, _, relative in candidates:
                 source = SOURCE_ROOT / relative
                 estimate = min(max(int(source.stat().st_size * 2.2), 1_000_000_000), 100_000_000_000)
-                free = os.statvfs(CACHE_ROOT).f_bavail * os.statvfs(CACHE_ROOT).f_frsize
-                if rank == 0 or free >= estimate:
+                if rank == 0 or self.cache_available() >= estimate:
                     selected = (rank == 0, relative)
                     break
             if not selected:

tests/test_core.py

@@ -64,6 +64,26 @@ class CoreTests(unittest.TestCase):
         source.write_bytes(b"changed")
         self.assertFalse(manager.cache_valid(relative))
 
+    def test_smaller_cache_limit_evicts_oldest_content(self):
+        m = self.module
+        manager = m.Manager()
+        relative = "movies/Resize/Resize.mkv"
+        source = self.root / "source" / relative
+        source.parent.mkdir(parents=True, exist_ok=True)
+        source.write_bytes(b"original")
+        output, manifest = manager.cache_paths(relative)
+        output.write_bytes(b"cached rendition")
+        manifest.write_text(json.dumps({"relative": relative, "source_fingerprint": m.fingerprint(source)}))
+        manager.ensure_link(relative, m.cache_target(relative))
+        old_limit = m.CACHE_MAX_BYTES
+        try:
+            m.CACHE_MAX_BYTES = 1
+            manager.enforce_cache_limit()
+        finally:
+            m.CACHE_MAX_BYTES = old_limit
+        self.assertFalse(output.exists())
+        self.assertEqual(os.readlink(self.root / "view" / relative), m.source_target(relative))
+
 
 if __name__ == "__main__":
     unittest.main()