Allow PORT override for GitLab webhook server

docs/docs/installation/gitlab.md

@@ -88,6 +88,7 @@ GITLAB__SHARED_SECRET=<shared_secret>
 GITLAB__URL=https://gitlab.com
 GITLAB__AUTH_TYPE=oauth_token  # Use "private_token" for older GitLab versions
 OPENAI__KEY=<your_openai_api_key>
+PORT=3000  # Optional: override the webhook server port
 ```
 
 8. Create a webhook in your GitLab project. Set the URL to `http[s]://<PR_AGENT_HOSTNAME>/webhook`, the secret token to the generated secret from step 3, and enable the triggers `push`, `comments` and `merge request events`.
@@ -152,4 +153,4 @@ AWS_SECRETS_MANAGER__SECRET_ARN=arn:aws:secretsmanager:us-east-1:123456789012:se
 
 **Important**: When using Secrets Manager, GitLab's webhook secret must be the Secrets Manager secret name.
 
-5. Add IAM permission `secretsmanager:GetSecretValue` to your Lambda execution role
+5. Add IAM permission `secretsmanager:GetSecretValue` to your Lambda execution role

pr_agent/servers/gitlab_webhook.py

@@ -1,5 +1,6 @@
 import copy
 import json
+import os
 import re
 from datetime import datetime
 
@@ -309,7 +310,23 @@ async def root():
 
 
 def start():
-    uvicorn.run(app, host="0.0.0.0", port=3000)
+    """
+    Start the GitLab webhook server.
+
+    The server port can be configured via the PORT environment variable.
+    Defaults to 3000 if PORT is not set or invalid.
+    """
+    raw_port = os.environ.get("PORT")
+    try:
+        port = int(raw_port) if raw_port else 3000
+        if not (1 <= port <= 65535):
+            raise ValueError(f"Port {port} is out of valid range")
+        if raw_port:
+            get_logger().info(f"Using custom PORT from environment: {port}")
+    except ValueError as e:
+        get_logger().warning(f"Invalid PORT environment variable ({e}), using default port 3000")
+        port = 3000
+    uvicorn.run(app, host="0.0.0.0", port=port)
 
 
 if __name__ == '__main__':

tests/unittest/test_gitlab_webhook_port.py

@@ -0,0 +1,46 @@
+import os
+from unittest import mock
+
+os.environ.setdefault("GITLAB__URL", "https://gitlab.example.com")
+import pr_agent.servers.gitlab_webhook as gitlab_webhook
+
+
+def test_start_uses_port_env(monkeypatch):
+    monkeypatch.setenv("PORT", "4567")
+
+    with mock.patch.object(gitlab_webhook.uvicorn, "run") as mock_run:
+        gitlab_webhook.start()
+
+    _, kwargs = mock_run.call_args
+    assert kwargs["port"] == 4567
+    assert kwargs["host"] == "0.0.0.0"
+
+
+def test_start_invalid_port_env(monkeypatch):
+    monkeypatch.setenv("PORT", "not-a-number")
+
+    with mock.patch.object(gitlab_webhook.uvicorn, "run") as mock_run:
+        gitlab_webhook.start()
+
+    _, kwargs = mock_run.call_args
+    assert kwargs["port"] == 3000
+
+
+def test_start_default_port(monkeypatch):
+    monkeypatch.delenv("PORT", raising=False)
+
+    with mock.patch.object(gitlab_webhook.uvicorn, "run") as mock_run:
+        gitlab_webhook.start()
+
+    _, kwargs = mock_run.call_args
+    assert kwargs["port"] == 3000
+
+
+def test_start_invalid_port_range(monkeypatch):
+    monkeypatch.setenv("PORT", "70000")
+
+    with mock.patch.object(gitlab_webhook.uvicorn, "run") as mock_run:
+        gitlab_webhook.start()
+
+    _, kwargs = mock_run.call_args
+    assert kwargs["port"] == 3000