mail: malloc_trim nach search_mail/read_attachment gegen RSS-Bloat

search_mail dekodiert bei breiten Queries den Body jeder Mail; CPython/glibc
gibt den Peak-RSS nicht ans OS zurueck -> Prozess wuchs auf 6.2 GB und hat
zusammen mit einem 2-TB-Restic-Lauf den Server-RAM/Swap gesprengt (restic OOM).
Fix: gc.collect()+malloc_trim(0) nach den speicherintensiven Tools.
Zusaetzlich systemd MemoryMax=2G/MemoryHigh=1.5G als Sicherheitsnetz (Drop-In, nicht im Repo).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

mail/server.py

@@ -7,6 +7,8 @@ import io
 import contextlib
 import imaplib
 import mailbox
+import gc
+import ctypes
 from email.header import decode_header
 from email.mime.text import MIMEText
 from email.utils import formatdate
@@ -47,6 +49,22 @@ mcp = FastMCP("Mail", stateless_http=True,
               transport_security={"enable_dns_rebinding_protection": False})
 
 
+try:
+    _libc = ctypes.CDLL("libc.so.6")
+except OSError:
+    _libc = None
+
+
+def _trim_memory():
+    """gc + malloc_trim: Speicher nach grossen Operationen ans OS zurueckgeben."""
+    gc.collect()
+    if _libc is not None:
+        try:
+            _libc.malloc_trim(0)
+        except Exception:
+            pass
+
+
 def _safe_decode(payload, charset):
     """Decode bytes robust gegen unbekannte/kaputte Charsets (z.B. 'x-unknown')."""
     if not isinstance(payload, bytes):
@@ -207,7 +225,9 @@ def search_mail(
                         continue
                 results.append(f"[{date_str}] {frm} -> {to}\n  Subject: {subj}\n  Account: {acct_name}, Folder: {fld}, Key: {key}")
                 if len(results) >= limit:
+                    _trim_memory()
                     return "\n\n".join(results)
+    _trim_memory()
     return "\n\n".join(results) if results else "No results found"
 
 
@@ -254,6 +274,7 @@ def read_attachment(
     attachment_index: Annotated[int, Field(description="Attachment number from the read_mail attachment list (1-based)")],
 ) -> list[TextContent | ImageContent | EmbeddedResource]:
     """Read an email attachment. Images shown inline, PDFs as extracted text, text directly, other documents as binary. Get the index from read_mail."""
+    _trim_memory()
     user = get_current_user()
     if not user:
         return [TextContent(type="text", text="Error: not authenticated")]