lua-resty-ffi-graphql-resolver

The openresty graphql server library that encapsulates ariadne.

Callflow example:

Highlights:

supports multiple data sources
- RESTful
- PostgreSQL
- Kafka
- WebService
- any other datasources to be implemented...
fully asynchronous
multiple schema instances
fully dynamic
- create and delete schema
- dynamic resolver mapping
jq expression to transform response body
zero code

Background

GraphQL is popular. Can we embed graphql server into openresty? In this way, we can not only enjoy the benefits brought by nginx high-performance proxy, but also request multiple different upstreams to generate the response content of graphql query without independent graphql server.

Ariadne is a brilliant python graphql server, which is schema-first and has simple but powerful APIs.

Why not encapsulate it so that we could reuse it in openresty?

lua-resty-ffi provides an efficient and generic API to do hybrid programming in openresty with mainstream languages (Go, Python, Java, Rust, Nodejs).

lua-resty-ffi-graphql-resolver = lua-resty-ffi + ariadne

Synopsis

Schema Config:

schema: graphql schema text
datasources
- <name> (fields other than @type is datasource specifc configuration fields)
  - @type: datasource type: http|sql|webservice|kafka
  - host: host name, including scheme, for http type only.
  - verify: verify ssl server name or not, optional, for http type only.
resolvers
- <GraphQL Type Name>
  - <type field name> (fields other than datasource is datasource specifc configuration fields)
    - datasource: reference name
    - uri: uri path, for http type only.
    - headers: request headers, optional, for http type only.
    - method: request method, optional, for http type only.
    - send_json_body: send graphql params in json body, or in uri arguemnts, optional, for http type only.
    - jq: jq expression to transform the response body for custom graphql output, optional, for http type only.

local schema, err = graphql_resolver.new({
    schema = "<graphql scehma text>",
    datasources = {
        nghttp2 = {
            ["@type"] = "http",
            host = "https://nghttp2.org",
            verify = true
        },
    },
    resolvers = {
        Query = {
            get = {
                datasource = "nghttp2",
                uri = "/httpbin/get",
                headers = {
                    foo = "xxx",
                    bar = "yyy"
                },
                method = "post",
                send_json_body = true,
                jq = "{url,agent:.headers.\"user-agent\"}"
            }
        }
    }
})

Query:

query: graphql query, mutation or subscription
variables: variables used in the query, optional

local ok, res, err = schema:query({
    query = "<graphql query string>",
    variables = {
        foo = "bar"
    }
})

Query Result:

Returns a tuple with two items:

bool: True when no errors occurred, False otherwise.
dict: an JSON-serializable dict with query result (defining either data, error, or both keys) that should be returned to client.

{ true, {
    data = {
      get = {
        origin = "192.168.1.1",
        uuid = "9fe7a61f-8c61-4299-b4a6-666788954b70-suffix"
      }
    }
  } }

Demo

Setup lua-resty-ffi-graphql-resolver

# install lua-resty-ffi
# https://github.com/kingluo/lua-resty-ffi#install-lua-resty-ffi-via-luarocks
# set `OR_SRC` to your openresty source path
luarocks config variables.OR_SRC /tmp/tmp.Z2UhJbO1Si/openresty-1.21.4.1
luarocks install lua-resty-ffi

# make lua-resty-ffi python loader library
apt install python3-dev python3-pip libffi-dev
cd /opt
git clone https://github.com/kingluo/lua-resty-ffi
cd /opt/lua-resty-ffi/examples/python
make

# install deps
cd /opt
git clone https://github.com/kingluo/lua-resty-ffi-graphql-resolver
cd /opt/lua-resty-ffi-graphql-resolver
pip3 install -r requirements.txt

# run nginx
cd /opt/lua-resty-ffi-graphql-resolver/demo
PATH=/opt/resty_ffi/nginx/sbin/:$PATH \
LD_LIBRARY_PATH=/opt/lua-resty-ffi/examples/python:/usr/local/lib/lua/5.1 \
PYTHONPATH=/opt/lua-resty-ffi-graphql-resolver \
nginx -p $PWD -c nginx.conf

Create schema

curl http://localhost:20000/create_schema -X POST -d '
{
    "schema": "type Get{origin:String!uuid:String}type Query{get:Get}type Post{url:String!agent:String!}type Mutation{post(data:String!):Post}",
    "datasources": {
        "nghttp2": {
            "@type": "http",
            "host": "https://nghttp2.org",
            "verify": true
        },
        "postman": {
            "@type": "http",
            "host": "https://postman-echo.com"
        }
    },
    "resolvers": {
        "Query": {
            "get": {
                "datasource": "nghttp2",
                "uri": "/httpbin/get",
                "headers": {
                    "foo": "xxx",
                    "bar": "yyy"
                }
            }
        },
        "Get": {
            "uuid": {
                "datasource": "nghttp2",
                "uri": "/httpbin/uuid",
                "jq": ".uuid + \"-suffix\""
            }
        },
        "Mutation": {
            "post": {
                "datasource": "postman",
                "uri": "/post",
                "method": "post",
                "send_json_body": true,
                "jq": "{url,agent:.headers.\"user-agent\"}"
            }
        }
    }
}' -s | jq

ouput:

{
  "schema": 1
}

Query

curl http://localhost:20000/query?schema=1 -X POST -d '
{
    "query": "query Test{get{origin uuid}}"
}' -s | jq

output:

[
  true,
  {
    "data": {
      "get": {
        "uuid": "95dbdfd0-1fcb-4428-8567-3ed0bea9aa7e-suffix",
        "origin": "192.168.1.1"
      }
    }
  }
]

Mutation

curl http://localhost:20000/query?schema=1 -X POST -d '
{
    "query": "mutation Test($data:String!){post(data:$data){url agent}}",
    "variables": {
        "data": "foobar"
    }
}' -s | jq

output:

[
  true,
  {
    "data": {
      "post": {
        "agent": "python-httpx/0.23.1",
        "url": "https://postman-echo.com/post"
      }
    }
  }
]

Close schema

curl http://localhost:20000/close_schema?schema=1

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