extract constants used in image server

scripts/vm/hypervisor/kvm/imageserver/backends/nbd.py

@@ -21,7 +21,13 @@ from typing import Any, Dict, List, Optional, Tuple
 
 import nbd
 
-from ..constants import CHUNK_SIZE, NBD_STATE_DIRTY, NBD_STATE_HOLE, NBD_STATE_ZERO
+from ..constants import (
+    CHUNK_SIZE,
+    NBD_BLOCK_STATUS_CHUNK,
+    NBD_STATE_DIRTY,
+    NBD_STATE_HOLE,
+    NBD_STATE_ZERO,
+)
 from ..util import merge_dirty_zero_extents
 from .base import BackendSession, ImageBackend
 
@@ -175,7 +181,7 @@ class NbdConnection:
             return [{"start": 0, "length": size, "zero": False}]
 
         allocation_extents: List[Dict[str, Any]] = []
-        chunk = min(size, 64 * 1024 * 1024)
+        chunk = min(size, NBD_BLOCK_STATUS_CHUNK)
         offset = 0
 
         def extent_cb(*args: Any, **kwargs: Any) -> int:
@@ -246,7 +252,7 @@ class NbdConnection:
 
         allocation_extents: List[Tuple[int, int, bool]] = []
         dirty_extents: List[Tuple[int, int, bool]] = []
-        chunk = min(size, 64 * 1024 * 1024)
+        chunk = min(size, NBD_BLOCK_STATUS_CHUNK)
         offset = 0
 
         def extent_cb(*args: Any, **kwargs: Any) -> int:

scripts/vm/hypervisor/kvm/imageserver/constants.py

@@ -26,5 +26,20 @@ NBD_STATE_DIRTY = 1
 MAX_PARALLEL_READS = 8
 MAX_PARALLEL_WRITES = 1
 
-CFG_DIR = "/tmp/imagetransfer"
+# HTTP server defaults
+DEFAULT_LISTEN_ADDRESS = "127.0.0.1"
+DEFAULT_HTTP_PORT = 54323
+
+# Control socket
 CONTROL_SOCKET = "/var/run/cloudstack/image-server.sock"
+CONTROL_SOCKET_BACKLOG = 32
+CONTROL_SOCKET_PERMISSIONS = 0o660
+CONTROL_RECV_BUFFER = 4096
+
+# Maximum size of a JSON body in a PATCH request (zero / flush ops)
+MAX_PATCH_JSON_SIZE = 64 * 1024  # 64 KiB
+
+# Byte range requested per block_status call for NBD extent queries
+NBD_BLOCK_STATUS_CHUNK = 64 * 1024 * 1024  # 64 MiB
+
+CFG_DIR = "/tmp/imagetransfer"

scripts/vm/hypervisor/kvm/imageserver/handler.py

@@ -26,7 +26,7 @@ from urllib.parse import parse_qs
 from .backends import NbdBackend, create_backend
 from .concurrency import ConcurrencyManager
 from .config import TransferRegistry
-from .constants import CHUNK_SIZE, MAX_PARALLEL_READS, MAX_PARALLEL_WRITES
+from .constants import CHUNK_SIZE, MAX_PARALLEL_READS, MAX_PARALLEL_WRITES, MAX_PATCH_JSON_SIZE
 from .util import is_fallback_dirty_response, json_bytes, now_s
 
 
@@ -422,7 +422,7 @@ class Handler(BaseHTTPRequestHandler):
         except ValueError:
             self._send_error_json(HTTPStatus.BAD_REQUEST, "Invalid Content-Length")
             return
-        if content_length <= 0 or content_length > 64 * 1024:
+        if content_length <= 0 or content_length > MAX_PATCH_JSON_SIZE:
             self._send_error_json(HTTPStatus.BAD_REQUEST, "Invalid Content-Length")
             return
 

scripts/vm/hypervisor/kvm/imageserver/server.py

@@ -33,7 +33,16 @@ except ImportError:
 
 from .concurrency import ConcurrencyManager
 from .config import TransferRegistry
-from .constants import CONTROL_SOCKET, MAX_PARALLEL_READS, MAX_PARALLEL_WRITES
+from .constants import (
+    CONTROL_RECV_BUFFER,
+    CONTROL_SOCKET,
+    CONTROL_SOCKET_BACKLOG,
+    CONTROL_SOCKET_PERMISSIONS,
+    DEFAULT_HTTP_PORT,
+    DEFAULT_LISTEN_ADDRESS,
+    MAX_PARALLEL_READS,
+    MAX_PARALLEL_WRITES,
+)
 from .handler import Handler
 
 
@@ -95,7 +104,7 @@ def _handle_control_conn(conn: socket.socket, registry: TransferRegistry) -> Non
     try:
         data = b""
         while True:
-            chunk = conn.recv(4096)
+            chunk = conn.recv(CONTROL_RECV_BUFFER)
             if not chunk:
                 break
             data += chunk
@@ -151,8 +160,8 @@ def _control_listener(registry: TransferRegistry, sock_path: str) -> None:
 
     srv = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
     srv.bind(sock_path)
-    os.chmod(sock_path, 0o660)
-    srv.listen(5)
+    os.chmod(sock_path, CONTROL_SOCKET_PERMISSIONS)
+    srv.listen(CONTROL_SOCKET_BACKLOG)
     logging.info("control socket listening on %s", sock_path)
 
     while True:
@@ -168,8 +177,8 @@ def main() -> None:
     parser = argparse.ArgumentParser(
         description="CloudStack image server backed by NBD / local file"
     )
-    parser.add_argument("--listen", default="127.0.0.1", help="Address to bind")
-    parser.add_argument("--port", type=int, default=54323, help="Port to listen on")
+    parser.add_argument("--listen", default=DEFAULT_LISTEN_ADDRESS, help="Address to bind")
+    parser.add_argument("--port", type=int, default=DEFAULT_HTTP_PORT, help="Port to listen on")
     parser.add_argument(
         "--control-socket",
         default=CONTROL_SOCKET,