Serialize gateway log compaction safely

resources/scripts/nap_install.py

@@ -863,7 +863,6 @@ def list_service(kind):
 def service_logs(kind, args):
     max_lines = int(cli_option(args, "--lines", "--tail", default="120"))
     path = service_log_path(kind)
-    compact_log_file(path)
     lines = log_tail_lines(path, max_lines=max_lines)
     status = "ok" if path.exists() else "missing"
     return {

resources/scripts/napseer_mcp_server.py

@@ -614,34 +614,35 @@ def compact_log_file(path, max_bytes):
     if max_bytes <= 0:
         return
     file_path = pathlib.Path(path)
-    try:
+    with GATEWAY_LOG_LOCK:
-        size = file_path.stat().st_size
+        try:
-    except FileNotFoundError:
+            size = file_path.stat().st_size
-        return
+        except FileNotFoundError:
-    except OSError:
+            return
-        return
+        except OSError:
-    if size <= max_bytes:
+            return
-        return
+        if size <= max_bytes:
-    try:
+            return
-        with file_path.open("rb") as handle:
+        try:
-            handle.seek(-max_bytes, os.SEEK_END)
+            with file_path.open("rb") as handle:
-            chunk = handle.read(max_bytes)
+                handle.seek(-max_bytes, os.SEEK_END)
-    except OSError:
+                chunk = handle.read(max_bytes)
-        return
+        except OSError:
-    newline_index = chunk.find(b"\n")
+            return
-    if newline_index >= 0 and newline_index + 1 < len(chunk):
+        newline_index = chunk.find(b"\n")
-        chunk = chunk[newline_index + 1 :]
+        if newline_index >= 0 and newline_index + 1 < len(chunk):
-    try:
+            chunk = chunk[newline_index + 1 :]
-        # Keep the inode stable: the daemon's stdout/stderr already point to
+        try:
-        # this file. Replacing the pathname would leave the live process
+            # Keep the inode stable: the daemon's stdout/stderr already point
-        # writing to a deleted inode and make `nap gateway logs` stale.
+            # to this file. The same lock covers the read/truncate interval so
-        with GATEWAY_LOG_LOCK, file_path.open("r+b") as handle:
+            # a concurrent gateway_log append cannot be discarded.
-            handle.seek(0)
+            with file_path.open("r+b") as handle:
-            handle.write(chunk)
+                handle.seek(0)
-            handle.truncate()
+                handle.write(chunk)
-            handle.flush()
+                handle.truncate()
-    except OSError:
+                handle.flush()
-        return
+        except OSError:
+            return
 
 
 def start_gateway_log_compactor_thread():

tests/test_cli_command_system.py

@@ -329,3 +329,15 @@ def test_cli_log_compaction_preserves_live_writer_inode(tmp_path):
     content = log_path.read_bytes()
     assert content.endswith(b"after-cli-compaction\n")
     assert b"recent-line\n" in content
+
+
+def test_logs_command_never_compacts_a_running_service_log(tmp_path, monkeypatch):
+    module = load_installer()
+    log_path = tmp_path / "gateway.log"
+    log_path.write_text("one\ntwo\n", encoding="utf-8")
+    monkeypatch.setattr(module, "service_log_path", lambda kind: log_path)
+    monkeypatch.setattr(module, "compact_log_file", fail_if_called)
+
+    result = module.service_logs("gateway", ["--lines", "1"])
+
+    assert result["lines"] == ["two"]