HTTP Dynamic

Basically, if we have data.json like this:

data.json

[  { id: "1", name: "Dan" },  { id: "2", name: "Lee" },  { id: "3", name: "Nick" },];

... and go run main.go, we can query records:

main.go

$ curl -g 'http://localhost:8080/graphql?query={user(name:"Dan"){id}}'{"data":{"user":{"id":"1"}}}

... now let's give Dan a surname:

data.json

[  { id: "1", name: "Dan", surname: "Jones" },  { id: "2", name: "Lee" },  { id: "3", name: "Nick" },];

... and kick the server:

kill -SIGUSR1 52114

And ask for Dan's surname:

$ curl -g 'http://localhost:8080/graphql?query={user(name:"Dan"){id,surname}}'{"data":{"user":{"id":"1","surname":"Jones"}}}

... or ask Jones's name and ID:

$ curl -g 'http://localhost:8080/graphql?query={user(surname:"Jones"){id,name}}'{"data":{"user":{"id":"1","name":"Dan"}}}

If you look at main.go, the file is not field-aware. That is, all it knows is how to work with []map[string]string type.

With this, we are not that far from exposing dynamic fields and filters which fully depend on what we have stored, all without changing our tooling.

Data

data.json

[  {    id: "1",    name: "Dan",    surname: "Jones",  },  {    id: "2",    name: "Lee",  },  {    id: "3",    name: "Nick",  },];

Main

main.go

package main
import (    "encoding/json"    "fmt"    "io/ioutil"    "net/http"    "os"    "os/signal"    "strconv"    "syscall"
    "github.com/graphql-go/graphql")
/*****************************************************************************//* Shared data variables to allow dynamic reloads/*****************************************************************************/
var schema graphql.Schema
const jsonDataFile = "data.json"
func handleSIGUSR1(c chan os.Signal) {    for {        <-c        fmt.Printf("Caught SIGUSR1. Reloading %s\n", jsonDataFile)        err := importJSONDataFromFile(jsonDataFile)        if err != nil {            fmt.Printf("Error: %s\n", err.Error())            return        }    }}
func filterUser(data []map[string]interface{}, args map[string]interface{}) map[string]interface{} {    for _, user := range data {        for k, v := range args {            if user[k] != v {                goto nextuser            }            return user        }
    nextuser:    }    return nil}
func executeQuery(query string, schema graphql.Schema) *graphql.Result {    result := graphql.Do(graphql.Params{        Schema:        schema,        RequestString: query,    })    if len(result.Errors) > 0 {        fmt.Printf("wrong result, unexpected errors: %v\n", result.Errors)    }    return result}
func importJSONDataFromFile(fileName string) error {    content, err := ioutil.ReadFile(fileName)    if err != nil {        return err    }
    var data []map[string]interface{}
    err = json.Unmarshal(content, &data)    if err != nil {        return err    }
    fields := make(graphql.Fields)    args := make(graphql.FieldConfigArgument)    for _, item := range data {        for k := range item {            fields[k] = &graphql.Field{                Type: graphql.String,            }            args[k] = &graphql.ArgumentConfig{                Type: graphql.String,            }        }    }
    var userType = graphql.NewObject(        graphql.ObjectConfig{            Name:   "User",            Fields: fields,        },    )
    var queryType = graphql.NewObject(        graphql.ObjectConfig{            Name: "Query",            Fields: graphql.Fields{                "user": &graphql.Field{                    Type: userType,                    Args: args,                    Resolve: func(p graphql.ResolveParams) (interface{}, error) {                        return filterUser(data, p.Args), nil                    },                },            },        })
    schema, _ = graphql.NewSchema(        graphql.SchemaConfig{            Query: queryType,        },    )
    return nil}
func main() {    // Catch SIGUSR1 and reload the data file    c := make(chan os.Signal, 1)    signal.Notify(c, syscall.SIGUSR1)    go handleSIGUSR1(c)
    err := importJSONDataFromFile(jsonDataFile)    if err != nil {        fmt.Printf("Error: %s\n", err.Error())        return    }
    http.HandleFunc("/graphql", func(w http.ResponseWriter, r *http.Request) {        result := executeQuery(r.URL.Query().Get("query"), schema)        json.NewEncoder(w).Encode(result)    })
    fmt.Println("Now server is running on port 8080")    fmt.Println("Test with Get      : curl -g 'http://localhost:8080/graphql?query={user(name:\"Dan\"){id,surname}}'")    fmt.Printf("Reload json file   : kill -SIGUSR1 %s\n", strconv.Itoa(os.Getpid()))    http.ListenAndServe(":8080", nil)}