App-Level Isolation in Web Server Config
Clace is a platform for developing and deploying internal tools. Clace provides functionality usually handled separately by a web server and an application server. The web server part of Clace is built such that there is complete isolation between app-level routing rules. Creating a new app or updating an existing app cannot break other apps. This post goes into details about how this is done and why it is useful.
A Web Server is software that accepts HTTP/HTTPS requests and routes them appropriately. Web Servers provide features like URL rewrites, reverse proxying, header manipulation, static file serving, and WebSocket connection handling. Web Servers can accept connections on multiple ports. A common pattern is that all requests are received on port 80 (for HTTP) and 443 (for HTTPS) and routing is done based on request domain (from the Host HTTP header) and path (from the url). Apache, Nginx, and Caddy are popular web servers.
Most web servers use a config file for specifying the rules for request routing. The config file is generally a DSL which specifies the API rules. Some servers like Caddy support JSON input. Encapsulating or grouping together rules related to an app is supported, but this encapsulation is not enforced. For updating the rules, the approach is to update the file on disk and send a reload request to the web server. Even for API based updates, the approach is usually to send the whole config contents, partial updates are not supported.
