---
title: Router radixtree
---

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### what's libradixtree?

[libradixtree](https://github.com/iresty/lua-resty-radixtree), adaptive radix trees implemented in Lua for OpenResty.

APISIX using libradixtree as route dispatching library.

### How to use libradixtree in APISIX?

This is Lua-Openresty implementation library base on FFI for [rax](https://github.com/antirez/rax).

Let's take a look at a few examples and have an intuitive understanding.

#### 1. Full match

```
/blog/foo
```

It will only match `/blog/foo`.

#### 2. Prefix matching

```
/blog/bar*
```

It will match the path with the prefix `/blog/bar`, eg: `/blog/bar/a`,
`/blog/bar/b`, `/blog/bar/c/d/e`, `/blog/bar` etc.

#### 3. Match priority

Full match -> Deep prefix matching.

Here are the rules:

```
/blog/foo/*
/blog/foo/a/*
/blog/foo/c/*
/blog/foo/bar
```

| path | Match result |
|------|--------------|
|/blog/foo/bar | `/blog/foo/bar` |
|/blog/foo/a/b/c | `/blog/foo/a/*` |
|/blog/foo/c/d | `/blog/foo/c/*` |
|/blog/foo/gloo | `/blog/foo/*` |
|/blog/bar | not match |

#### 4. Parameter match

When `radixtree_uri_with_parameter` is used, we can match routes with parameters.

For example, with configuration:

```yaml
apisix:
    router:
        http: 'radixtree_uri_with_parameter'
```

route like

```
/blog/:name
```

will match both `/blog/dog` and `/blog/cat`.

For more details, see https://github.com/api7/lua-resty-radixtree/#parameters-in-path.

### How to filter route by Nginx builtin variable

Please take a look at [radixtree-new](https://github.com/iresty/lua-resty-radixtree#new),
here is an simple example:

```shell
$ curl http://127.0.0.1:9080/apisix/admin/routes/1 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -i -d '
{
    "uri": "/index.html",
    "vars": [
        ["http_host", "==", "iresty.com"],
        ["cookie_device_id", "==", "a66f0cdc4ba2df8c096f74c9110163a9"],
        ["arg_name", "==", "json"],
        ["arg_age", ">", "18"],
        ["arg_address", "~~", "China.*"]
    ],
    "upstream": {
        "type": "roundrobin",
        "nodes": {
            "39.97.63.215:80": 1
        }
    }
}'
```

This route will require the request header `host` equal `iresty.com`, request cookie key `_device_id` equal `a66f0cdc4ba2df8c096f74c9110163a9` etc.

### How to filter route by graphql attributes

APISIX supports filtering route by some attributes of graphql. Currently we support:

* graphql_operation
* graphql_name
* graphql_root_fields

For instance, with graphql like this:

```graphql
query getRepo {
    owner {
        name
    }
    repo {
        created
    }
}
```

* The `graphql_operation` is `query`
* The `graphql_name` is `getRepo`,
* The `graphql_root_fields` is `["owner", "repo"]`

We can filter such route out with:

```shell
$ curl http://127.0.0.1:9080/apisix/admin/routes/1 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -i -d '
{
    "methods": ["POST"],
    "uri": "/_graphql",
    "vars": [
        ["graphql_operation", "==", "query"],
        ["graphql_name", "==", "getRepo"],
        ["graphql_root_fields", "has", "owner"]
    ],
    "upstream": {
        "type": "roundrobin",
        "nodes": {
            "39.97.63.215:80": 1
        }
    }
}'
```

To prevent spending too much time reading invalid graphql request body, we only read the first 1 MiB
data from the request body. This limitation is configured via:

```yaml
graphql:
  max_size: 1048576

```

If you need to pass a graphql body which is larger than the limitation, you can increase the value in `conf/config.yaml`.