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7.06.Routers.md

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Routers

Router determines how requests are routed to the corresponding Pipeline for subsequent processing. We currently support two routing strategies, Ordered and RadixTree, and you can choose a Router that suits your needs based on its characteristics, and we also provide the ability to customize Router, if the built-in Router does not meet your needs, you can choose Write a custom Router.

Ordered

Ordered router is the default router for httpserver, as the name implies, its matching rules are in the order of the route definition.

Let's look at some examples to better understand the strategy.

kind: HTTPServer
name: server-demo
port: 10080
keepAlive: true
https: false
routerKind: Ordered
rules:
  - paths:
    - path: /pipeline/abc
      backend: static-backend
    - pathRegexp: `^/pipeline/regexp$`
      backend: regexp-backend
    - pathPrefix: /pipeline
      backend: prefix-backend
path Match backend
/pipeline/abc static-backend
/pipeline/regexp regexp-backend
/pipeline/test prefix-backend
/pipeline/test prefix-backend
/blog/bar not match

Take a look at another example.

kind: HTTPServer
name: server-demo
port: 10080
keepAlive: true
https: false
routerKind: Ordered
rules:
  - paths:
    - pathPrefix: /pipeline
      backend: prefix-backend
    - path: /pipeline/abc
      backend: static-backend
    - pathRegexp: `^/pipeline/regexp$`
      backend: regexp-backend
path Match backend
/pipeline/abc prefix-backend
/pipeline/regexp prefix-backend
/pipeline/test prefix-backend
/pipeline/test prefix-backend
/blog/bar not match

It is clear to see that the matching rules of the router are matched in the order of route definition, and the matching stops when the result is reached.

RadixTree

As the name implies, you can see that the underlying mechanism of the router uses a Radix tree

Still in the same way, let's use some examples to better understand the strategy.

1. Full match

/users/aniaan

This rule will only match /users/aniaan

2. Prefix match

/users/*

This rule will match all paths prefixed with /users, eg: /users/aniaan, /users/localvar, /users/megaease/abc

3. Parameter match

/users/{username}/hovercard

This rule will match /users/aniaan/hovercard and /users/localvar/hovercard

4. Regexp match

/users/{username:[a-z]+}/hovercard

This rule will match /users/aniaan/hovercard and /users/localvar/hovercard, not /users/123/hovercard.

5. Match priority

Full match -> Regexp match -> Parameter match -> Prefix match

Let's look at an example to get a better impression.

kind: HTTPServer
name: server-demo
port: 10080
keepAlive: true
https: false
routerKind: RadixTree
rules:
  - paths:
    - path: /users/{username}/hovercard
      backend: parameter-path-backend
    - path: /users/{username:[a-z]+}/hovercard
      backend: regexp-backend
    - path: /users/*
      backend: prefix-backend
    - path: /users/aniaan/hovercard
      backend: full-match-backend
path Match backend
/users/aniaan/hovercard full-match-backend
/users/12345/hovercard parameter-path-backend
/users/localvar/hovercard regexp-backend
/users/test prefix-backend
/blog/bar not match

Let's take a look at another example to deepen our understanding

kind: HTTPServer
name: server-demo
port: 10080
keepAlive: true
https: false
routerKind: RadixTree
rules:
  - paths:
    - path: /user/{username}/123
      backend: h1
    - path: /user/wang/{num}
      backend: h2
    - path: /{type}/wang/123
      backend: h3

/user/wang/123 will match /user/wang/{num}, which is determined by the matching order of RadixTree, you can split the path into individual characters, each character follows the matching order of Full match -> Regexp match -> Parameter match -> Prefix match, so the final match result is /user/wang/{num}.

RadixTree, compared with Ordered, has lost its definition order.

See one more.

kind: HTTPServer
name: server-demo
port: 10080
keepAlive: true
https: false
routerKind: RadixTree
- paths:
    - path: /users/{u:[a-z]+}sername/hovercard
      backend: h1
    - path: /users/u{sername}/hovercard
      backend: h2

Similarly, /users/username/hovercard will match /users/u{sername}/hovercard for the same reason as above, so you can try to understand it.

Rewrite

Let's take a look at how RadixTree's Path Rewrite feature works. The syntax of Rewrite remains basically the same as that of Path, with a few minor differences.

kind: HTTPServer
name: server-demo
port: 10080
keepAlive: true
https: false
routerKind: RadixTree
rules:
  - paths:
    - path: /users/{username}/hovercard
      rewriteTarget: /api/users/{username}/card
      backend: parameter-path-backend
    - path: /users/{username:[a-z]+}/hovercard
      rewriteTarget: /api/users/{username}/card
      backend: regexp-backend
    - path: /users/*
      rewriteTarget: /api/users/{EG_WILDCARD}
      backend: prefix-backend
    - path: /users/aniaan/hovercard
      rewriteTarget: /api/users/aniaan/card
      backend: full-match-backend
path Match backend Rewrite target
/users/aniaan/hovercard full-match-backend /api/users/aniaan/card
/users/12345/hovercard parameter-path-backend /api/users/12345/card
/users/localvar/hovercard regexp-backend /api/users/localvar/card
/users/test prefix-backend /api/users/test

You can see that only the wildcard * needs to be replaced by the built-in variable EG_WILDCARD.