API to return a selected field with /only?filed=XX (#12)

* API to return a selected field with /only?filed=XX

* readme

README.md

@@ -87,13 +87,20 @@ yas-nyan@mptcp:~$ curl localhost:8931
 
 - you can filter record with query params.
 
+for all fileds.
 ```
-- 
 curl localhost:8931/?dport=5201
 curl localhost:8931/?src=2001:db8::1
 curl localhost:8931/?src=2001:db8::1&dst=64:ff9b::192.0.2.1
 ```
 
+One optional field
+
+```
+curl localhost:8931/only?field=Mss
+curl localhost:8931/only?filed=Minrtt?src=2001:db8::1
+```
+
 ## config and args
 
 - args

go.mod

@@ -20,7 +20,10 @@ require (
 	github.com/jackc/pgx/v5 v5.4.2 // indirect
 	github.com/jinzhu/inflection v1.0.0 // indirect
 	github.com/jinzhu/now v1.1.5 // indirect
+	github.com/k0kubun/pp v3.0.1+incompatible // indirect
 	github.com/magiconair/properties v1.8.7 // indirect
+	github.com/mattn/go-colorable v0.1.12 // indirect
+	github.com/mattn/go-isatty v0.0.14 // indirect
 	github.com/mitchellh/mapstructure v1.5.0 // indirect
 	github.com/pelletier/go-toml/v2 v2.0.8 // indirect
 	github.com/spf13/afero v1.9.5 // indirect

go.sum

@@ -140,6 +140,8 @@ github.com/jinzhu/now v1.1.5 h1:/o9tlHleP7gOFmsnYNz3RGnqzefHA47wQpKrrdTIwXQ=
 github.com/jinzhu/now v1.1.5/go.mod h1:d3SSVoowX0Lcu0IBviAWJpolVfI5UJVZZ7cO71lE/z8=
 github.com/jstemmer/go-junit-report v0.0.0-20190106144839-af01ea7f8024/go.mod h1:6v2b51hI/fHJwM22ozAgKL4VKDeJcHhJFhtBdhmNjmU=
 github.com/jstemmer/go-junit-report v0.9.1/go.mod h1:Brl9GWCQeLvo8nXZwPNNblvFj/XSXhF0NWZEnDohbsk=
+github.com/k0kubun/pp v3.0.1+incompatible h1:3tqvf7QgUnZ5tXO6pNAZlrvHgl6DvifjDrd9g2S9Z40=
+github.com/k0kubun/pp v3.0.1+incompatible/go.mod h1:GWse8YhT0p8pT4ir3ZgBbfZild3tgzSScAn6HmfYukg=
 github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
 github.com/kr/fs v0.1.0/go.mod h1:FFnZGqtBN9Gxj7eW1uZ42v5BccTP0vu6NEaFoC2HwRg=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
@@ -149,6 +151,10 @@ github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/magiconair/properties v1.8.7 h1:IeQXZAiQcpL9mgcAe1Nu6cX9LLw6ExEHKjN0VQdvPDY=
 github.com/magiconair/properties v1.8.7/go.mod h1:Dhd985XPs7jluiymwWYZ0G4Z61jb3vdS329zhj2hYo0=
+github.com/mattn/go-colorable v0.1.12 h1:jF+Du6AlPIjs2BiUiQlKOX0rt3SujHxPnksPKZbaA40=
+github.com/mattn/go-colorable v0.1.12/go.mod h1:u5H1YNBxpqRaxsYJYSkiCWKzEfiAb1Gb520KVy5xxl4=
+github.com/mattn/go-isatty v0.0.14 h1:yVuAays6BHfxijgZPzw+3Zlu5yQgKGP2/hcQbHb7S9Y=
+github.com/mattn/go-isatty v0.0.14/go.mod h1:7GGIvUiUoEMVVmxf/4nioHXj79iQHKdU27kJ6hsGG94=
 github.com/mitchellh/mapstructure v1.5.0 h1:jeMsZIYE/09sWLaz43PL7Gy6RuMjD2eJVyuac5Z2hdY=
 github.com/mitchellh/mapstructure v1.5.0/go.mod h1:bFUtVrKA4DC2yAKiSyO/QUcy7e+RRV2QTWOzhPopBRo=
 github.com/pelletier/go-toml/v2 v2.0.8 h1:0ctb6s9mE31h0/lhu+J6OPmVeDxJn+kYnJc2jZR9tGQ=
@@ -345,6 +351,8 @@ golang.org/x/sys v0.0.0-20210423082822-04245dca01da/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20210423185535-09eb48e85fd7/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210510120138-977fb7262007/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20210927094055-39ccf1dd6fa6/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220908164124-27713097b956/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.10.0 h1:SqMFp9UcQJZa+pmYuAKjd9xq1f0j5rLcDIk0mj4qAsA=
 golang.org/x/sys v0.10.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=

pkg/sockmon/app.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"net/http"
 	"os/exec"
+	"reflect"
 
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
@@ -84,6 +85,7 @@ func fn(cmd *cobra.Command, args []string) error {
 	go func() {
 		http.HandleFunc("/", handlerDefault)
 		http.HandleFunc("/rtt", handlerRttOnly)
+		http.HandleFunc("/only", handerByFieldName)
 		if err := http.ListenAndServe(bindAddress, nil); err != nil {
 			log.Fatalf("Invalid bind address. err: %s", err)
 		}
@@ -157,14 +159,72 @@ func input(in string) {
 	}
 }
 
+func handerByFieldName(w http.ResponseWriter, r *http.Request) {
+	params := r.URL.Query()
+
+	c := FilterByParams(params, cache)
+
+	onlyParams, ok := params["field"]
+	if !ok {
+		http.Error(w, "Missing ?field= query parameter", http.StatusBadRequest)
+		return
+	}
+
+	// パラメータは一つと仮定する
+	onlyFiled := onlyParams[0]
+
+	// onlyFiledがExtに存在するかチェック
+	v := reflect.ValueOf(SocketExtendedInformation{})
+	vf := v.FieldByName(onlyFiled)
+	if !(vf.IsValid()) {
+		http.Error(w, fmt.Sprintf("Invalid input ?filed=%s", onlyFiled), http.StatusBadRequest)
+		return
+	}
+
+	// 返信用のmapを作る
+	fieldType := vf.Type()
+	mapType := reflect.MapOf(reflect.TypeOf(""), fieldType) // map[string]<filedType>
+	rtnMap := reflect.MakeMap(mapType)
+
+	for k, v := range c {
+		extVal := reflect.ValueOf(v.Ext)
+		// .ExtがSocketに存在しない場合。これは絶対に起こり得ないが、reflectionしているので念のため。
+		if extVal.Kind() != reflect.Struct {
+			log.Errorf("An exception occurred that should never have happened during reflection.  extVal.Kind: %s  reflect.Struct: %s", extVal.Kind(), reflect.Struct)
+			http.Error(w, fmt.Sprintf("Unexpected type for Ext in Socket %s", k), http.StatusInternalServerError)
+			return
+		}
+		// ここも事前にチェックしているが、reflectionしているので念のため。
+		val := extVal.FieldByName(onlyFiled)
+		if !val.IsValid() {
+			log.Errorf("An exception occurred that should never have happened during reflection. extVal.Kind: %s  reflect.Struct: %s", extVal.Kind(), reflect.Struct)
+			http.Error(w, fmt.Sprintf("Field %s does not exist in Socket %s", onlyFiled, k), http.StatusInternalServerError)
+			return
+		}
+
+		rtnMap.SetMapIndex(reflect.ValueOf(k), val)
+	}
+
+	// rtnMapをInterfaceに変換してjsonにエンコード
+	out, err := json.MarshalIndent(rtnMap.Interface(), "", "  ")
+	if err != nil {
+		http.Error(w, fmt.Sprintf("Failed to encode result: %v", err), http.StatusInternalServerError)
+		return
+	}
+
+	io.WriteString(w, string(out))
+	return
+
+}
+
 func handlerDefault(w http.ResponseWriter, r *http.Request) {
-	// filter by query parameters
 	params := r.URL.Query()
+
 	c := FilterByParams(params, cache)
-	out, err := json.MarshalIndent(&c, "", "  ")
 
+	out, err := json.MarshalIndent(&c, "", "  ")
 	if err != nil {
-		io.WriteString(w, fmt.Sprintf("{'err':'%s'}\n", err.Error()))
+		http.Error(w, fmt.Sprintf("Failed to encode result: %v", err), http.StatusInternalServerError)
 		return
 	}
 	io.WriteString(w, fmt.Sprintf("%s\n", string(out)))
@@ -182,7 +242,7 @@ func handlerRttOnly(w http.ResponseWriter, r *http.Request) {
 
 	out, err := json.MarshalIndent(&rttcache, "", "  ")
 	if err != nil {
-		io.WriteString(w, fmt.Sprintf("{'err':'%s'}\n", err.Error()))
+		http.Error(w, fmt.Sprintf("Failed to encode result: %v", err), http.StatusInternalServerError)
 		return
 	}
 	io.WriteString(w, fmt.Sprintf("%s\n", string(out)))