Jenkins reload

[ip1981]

Objective: make Jenkins able to deploy itself. This requires graceful shutdown after all jobs are done. Then systemd will start Jenkins again, probably new version of it.

Jenkins may expose unprotected URL endpoint to trigger shutdown. This is to be used by automated scripts in Jenkins app itself. "Unprotected" means that the URL or credentials (or maybe UNIX socket) is only known to Jenkins user.

Possible implementation:

1. "backdoor" plugin injected on each deploy in addition to any other plugins.
2. This plugin exposes the endpoint URL like /<secret>/shutdown. The <secret> is new on each start and is written to a private file.
3. When configuration is changed, a script reads the secret file, finds the URL and hits it.