http-api: T8235: Use asyncio lock to prevent deadlock in config-file handler

The HTTPS API config-file handler previously used a blocking
threading.Lock in an async FastAPI endpoint, which can block the
event loop and make the API unresponsive under concurrent load.

This commit replaces the blocking lock with an asyncio.Lock to
serialize config operations without blocking async execution,
resolving the reported deadlock when concurrent /config-file
load operations occur.

The behavior of run_in_threadpool and background task scheduling
remains consistent with prior logic, so the handler preserves
existing commit and commit-confirm semantics.

1 files changed, 50 insertions, 53 deletions

diff --git a/src/services/api/rest/routers.py b/src/services/api/rest/routers.py
index c8102c980..25c29b4c3 100644
--- a/src/services/api/rest/routers.py
+++ b/src/services/api/rest/routers.py
@@ -18,6 +18,7 @@
 # pylint: disable=wildcard-import,unused-wildcard-import
 # pylint: disable=broad-exception-caught
 
+import asyncio
 import json
 import copy
 import logging
@@ -85,6 +86,7 @@ LOG = logging.getLogger('http_api.routers')
 
 lock = Lock()
 
+asynclock = asyncio.Lock()
 
 def check_auth(key_list, key):
     key_id = None
@@ -664,68 +666,63 @@ async def config_file_op(data: ConfigFileModel, background_tasks: BackgroundTask
     # A non-zero confirm_time will start commit-confirm timer on commit
     confirm_time = data.confirm_time
 
-    lock.acquire()
+    # Serialize config operations without blocking the event loop
+    async with asynclock:
+        try:
+            if op == 'save':
+                path = data.file or '/config/config.boot'
+                msg = session.save_config(path)
+
+            elif op in ('load', 'merge'):
+                if data.file:
+                    path = data.file
+                elif data.string:
+                    path = '/tmp/config.file'
+                    with open(path, 'w') as f:
+                        f.write(data.string)
+                else:
+                    return error(400, 'Missing required field "file | string"')
 
-    try:
-        if op == 'save':
-            if data.file:
-                path = data.file
-            else:
-                path = '/config/config.boot'
-            msg = session.save_config(path)
-        elif op in ('load', 'merge'):
-            if data.file:
-                path = data.file
-            elif data.string:
-                path = '/tmp/config.file'
-                with open(path, 'w') as f:
-                    f.write(data.string)
-            else:
-                return error(400, 'Missing required field "file | string"')
+                match op:
+                    case 'load':
+                        session.migrate_and_load_config(path)
+                    case 'merge':
+                        session.merge_config(path, destructive=data.destructive)
 
-            match op:
-                case 'load':
-                    session.migrate_and_load_config(path)
-                case 'merge':
-                    session.merge_config(path, destructive=data.destructive)
+                config = Config(session_env=env)
+                d = get_config_diff(config)
 
-            config = Config(session_env=env)
-            d = get_config_diff(config)
+                state.confirm_time = confirm_time if confirm_time else 0
 
-            state.confirm_time = confirm_time if confirm_time else 0
+                if not d.is_node_changed(['service', 'https']):
+                    if confirm_time:
+                        out, err = await run_in_threadpool(run_commit_confirm, state)
+                    else:
+                        out, err = await run_in_threadpool(run_commit, state)
 
-            if not d.is_node_changed(['service', 'https']):
-                if confirm_time:
-                    out, err = await run_in_threadpool(run_commit_confirm, state)
                     if err:
                         raise err
-                    msg = msg + out if msg else out
+                    msg = (msg or '') + (out or '')
                 else:
-                    out, err = await run_in_threadpool(run_commit, state)
-                    if err:
-                        raise err
-                    msg = msg + out if msg else out
+                    if confirm_time:
+                        background_tasks.add_task(call_commit_confirm, state)
+                    else:
+                        background_tasks.add_task(call_commit, state)
+                    out = self_ref_msg
+                    msg = (msg or '') + (out or '')
+            elif op == 'confirm':
+                msg = session.confirm()
             else:
-                if confirm_time:
-                    background_tasks.add_task(call_commit_confirm, state)
-                else:
-                    background_tasks.add_task(call_commit, state)
-                out = self_ref_msg
-                msg = msg + out if msg else out
-
-        elif op == 'confirm':
-            msg = session.confirm()
-        else:
-            return error(400, f"'{op}' is not a valid operation")
-    except ConfigSessionError as e:
-        return error(400, str(e))
-    except Exception:
-        LOG.critical(traceback.format_exc())
-        return error(500, 'An internal error occured. Check the logs for details.')
-    finally:
-        if 'IN_COMMIT_CONFIRM' in env:
-            del env['IN_COMMIT_CONFIRM']
-        lock.release()
+                return error(400, f"'{op}' is not a valid operation")
+
+        except ConfigSessionError as e:
+            return error(400, str(e))
+        except Exception:
+            LOG.critical(traceback.format_exc())
+            return error(500, 'An internal error occured. Check the logs for details.')
+        finally:
+            if 'IN_COMMIT_CONFIRM' in env:
+                del env['IN_COMMIT_CONFIRM']
 
     return success(msg)