api: avoid restart loop on config errors

gateway/etc/systemd/system/eterban-api.service

@@ -7,6 +7,7 @@ Type=simple
 ExecStart=/usr/bin/python3 /usr/share/eterban/eterban_api.py
 Restart=always
 RestartSec=5
+RestartPreventExitStatus=78
 
 [Install]
 WantedBy=multi-user.target

gateway/usr/share/eterban/eterban_api.py

@@ -138,19 +138,23 @@ def main():
     host = LISTEN_HOST
     port = LISTEN_PORT
 
-    # Allow override from config
-    if os.path.exists(path_to_config):
-        config = configparser.ConfigParser()
-        config.read(path_to_config)
-        host = config.get('API', 'listen_host', fallback=LISTEN_HOST)
-        port = config.getint('API', 'listen_port', fallback=LISTEN_PORT)
-        API_TOKEN = config.get('API', 'api_token', fallback='').strip()
-        API_RATE_LIMIT = config.getint('API', 'rate_limit_per_minute', fallback=60)
-
-    if not is_loopback_host(host) and not API_TOKEN:
-        raise RuntimeError('API token is required for a non-loopback listen_host')
-    if API_RATE_LIMIT < 1:
-        raise RuntimeError('API rate_limit_per_minute must be positive')
+    try:
+        # Allow override from config
+        if os.path.exists(path_to_config):
+            config = configparser.ConfigParser()
+            config.read(path_to_config)
+            host = config.get('API', 'listen_host', fallback=LISTEN_HOST)
+            port = config.getint('API', 'listen_port', fallback=LISTEN_PORT)
+            API_TOKEN = config.get('API', 'api_token', fallback='').strip()
+            API_RATE_LIMIT = config.getint('API', 'rate_limit_per_minute', fallback=60)
+
+        if not is_loopback_host(host) and not API_TOKEN:
+            raise ValueError('API token is required for a non-loopback listen_host')
+        if API_RATE_LIMIT < 1:
+            raise ValueError('API rate_limit_per_minute must be positive')
+    except (ValueError, configparser.Error) as error:
+        print('Invalid Eterban API configuration: ' + str(error), file=sys.stderr)
+        raise SystemExit(78)
 
     server = http.server.HTTPServer((host, port), EterbanAPIHandler)
     print(f"Eterban API listening on {host}:{port}")

tests/static-checks.sh

@@ -41,3 +41,14 @@ if [ "$status" -ne 78 ]; then
     echo "internal service without configuration returned $status, expected 78" >&2
     exit 1
 fi
+
+if printf '%s\n' '[API]' 'rate_limit_per_minute = 0' | (cd gateway/usr/share/eterban && python3 -c 'from pathlib import Path; p = Path("eterban_api.py"); code = p.read_text().replace("/etc/eterban/settings.ini", "/proc/self/fd/0"); exec(compile(code, str(p), "exec"))') >/dev/null 2>&1; then
+    echo 'API service with invalid configuration must fail' >&2
+    exit 1
+else
+    status=$?
+fi
+if [ "$status" -ne 78 ]; then
+    echo "API service with invalid configuration returned $status, expected 78" >&2
+    exit 1
+fi