Make the srcindex server exit after some time being idle

Saves resources when the editing session ends (if used with systemd
socket activation, otherwise it's best to set --timeout=0).

ecopilot_srcindex/http.py

@@ -2,6 +2,7 @@ import argparse
 import git
 import logging
 import os
+import threading
 from flask import Flask, request, make_response
 from werkzeug.serving import make_server
 
@@ -10,6 +11,7 @@ from ecopilot_srcindex.repomap import RepoMap
 
 
 app = Flask(__name__)
+mutex = threading.Lock()
 
 
 @app.route('/', methods=('POST',))
@@ -33,12 +35,16 @@ class Service:
         self.repo_map_cache = {}
 
     def handle_request(self, git_root, chat_fnames):
+        if app.watchdog:
+            app.watchdog.reset()
+
         repo = git.Repo(git_root, search_parent_directories=True)
         git_root = repo.working_tree_dir
         abs_src_paths = [
             os.path.join(git_root, entry)
             for entry in repo.git.ls_files().split('\n')]
 
+        with mutex:
             if git_root not in self.repo_map_cache:
                 self.repo_map_cache[git_root] = RepoMap(
                     map_tokens=self.map_tokens,
@@ -49,6 +55,35 @@ class Service:
             return repo_map.get_ranked_tags_map(chat_fnames, abs_src_paths)
 
 
+class _watchdog():
+
+    def __init__(self, fn, timeout):
+        self._timeout = timeout
+        self._fn = fn
+        self._start()
+
+    def _start(self):
+        self._timer = threading.Timer(self._timeout, self._fn)
+        self._timer.start()
+
+    def reset(self):
+        self._timer.cancel()
+        self._start()
+
+
+def _run_server_with_watchdog(srv, app, timeout):
+    if timeout <= 0:
+        app.watchdog = None
+    else:
+        def _stop():
+            srv.shutdown()
+
+        app.watchdog = _watchdog(_stop, timeout)
+
+    srv.log_startup()
+    srv.serve_forever()
+
+
 def main():
     parser = argparse.ArgumentParser(description='''
 
@@ -66,6 +101,9 @@ HTTP service for contextual code indexing.
     parser.add_argument(
         '--map-tokens', metavar='N', type=int, default=1024,
         help='Map tokens limit (default: %(default)s)')
+    parser.add_argument(
+        '--timeout', metavar='SECONDS', type=int, default=600,
+        help='Exit after idle time (0 to disable)')
     args = parser.parse_args()
 
     logging.basicConfig(level=logging.DEBUG)
@@ -81,8 +119,7 @@ HTTP service for contextual code indexing.
         # systemd activated socket (which we expect will be fd 3).
         srv = make_server(
             '127.0.0.1', 7894, app, fd=3)
-        srv.log_startup()
-        srv.serve_forever()
+        _run_server_with_watchdog(srv, app, args.timeout)
 
 
 if __name__ == '__main__':