HTTP multiplexer
HTTP Multiplexer or HTTP Request multiplexing is a technique by which an incoming HTTP request from a user agent is matched against registered patterns or routes, and the callback request handler is invoked for the best match.[1][note 1][2]
Functioning of the Multiplexer
The HTTP application router or multiplexer relies on a tree data structure, which makes use of Radix tree or prefix tree. For example:
| Priority | Path | Request Handler |
|---|---|---|
| 9 | / | Index |
| 8 | /s | Index (no transition) |
| 1 | /search/ | Search |
| 1 | /support/ | Support |
| 2 | /blog/ | BlogIndex |
| 1 | /blog/{\w+} | BlogIndex (no transition) |
| 1 | /blog/{\w+}/ | Blog |
| 2 | /contact-us/ | GeneralContact |
| 1 | /contact-us/pr/ | PRContact |
Implementation
Every Request Handler is a callback function or a function pointer memory address that is registered to handle that HTTP endpoint. The placeholder or parameter for the endpoint is usually implemented using a state machine which accepts characters until it reaches a sentinel value i.e. '/' (forward-slash). The transition between each states updates the request handler callback that will be invoked. Since a pattern ending in a slash names a rooted subtree, the pattern "/" matches all paths not matched by other registered patterns, not just the URL with Path == "/".
Common features
Few of the common features of a HTTP multiplexer include:
- Request routing based on URL host, request path, path prefix, schemes, header, query values, HTTP method declaration and wildcard routes.
- Registered routes can be used as subroutes i.e. nested routing is only tested if the parent route matches. This is useful when defining a group of routes that share common conditions like HTTP Host header and prefix path.
- URL hosts, request paths, and query values can have placeholders for dynamic request processing, with optional regular expressions.
External Links
- Example of HTTP multiplexers and routers
Notes
References
- ↑ Szucs, Sandos (2018). "Modern HTTP Routing" (PDF). USENIX.
- ↑ Yellavula, Naren (2017). Building RESTful Web services with Go: Learn how to build powerful RESTful APIs with Golang that scale gracefully. Paket Publishing. ISBN 9781788291088. Search this book on
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