add plugin gw-error-format (#116)

Co-authored-by: 澄潭 <zty98751@alibaba-inc.com>

plugins/wasm-go/extensions/gw-error-format/main.go

@@ -0,0 +1,98 @@
+package main
+
+import (
+	"errors"
+
+	"github.com/alibaba/higress/plugins/wasm-go/pkg/wrapper"
+	"github.com/tetratelabs/proxy-wasm-go-sdk/proxywasm"
+	"github.com/tetratelabs/proxy-wasm-go-sdk/proxywasm/types"
+	"github.com/tidwall/gjson"
+)
+
+func main() {
+	wrapper.SetCtx(
+		"gw-error-format",
+		wrapper.ParseConfigBy(parseConfig),
+		wrapper.ProcessResponseHeadersBy(onHttpResponseHeader),
+		wrapper.ProcessResponseBodyBy(onHttpResponseBody),
+	)
+}
+
+type MyConfig struct {
+	rules      []gjson.Result
+	set_header []gjson.Result
+}
+
+func parseConfig(json gjson.Result, config *MyConfig, log wrapper.Log) error {
+	config.set_header = json.Get("set_header").Array()
+	config.rules = json.Get("rules").Array()
+	for _, item := range config.rules {
+		log.Info("config.rules: " + item.String())
+		if item.Get("match.statuscode").String() == "" {
+			return errors.New("missing match.statuscode in config")
+		}
+		if item.Get("replace.statuscode").String() == "" {
+			return errors.New("missing replace.statuscode in config")
+		}
+	}
+
+	return nil
+}
+
+func onHttpResponseHeader(ctx wrapper.HttpContext, config MyConfig, log wrapper.Log) types.Action {
+	dontReadResponseBody := false
+	currentStatuscode, _ := proxywasm.GetHttpResponseHeader(":status")
+
+	for _, item := range config.rules {
+		configMatchStatuscode := item.Get("match.statuscode").String()
+		configReplaceStatuscode := item.Get("replace.statuscode").String()
+		switch currentStatuscode {
+		// configMatchStatuscode value example: "403" or "503":
+		case configMatchStatuscode:
+			// If the response header `x-envoy-upstream-service-time`  is not found,  the request has  not  been  forwarded to the  backend  service
+			_, err := proxywasm.GetHttpResponseHeader("x-envoy-upstream-service-time")
+			if err != nil {
+				proxywasm.RemoveHttpResponseHeader("content-length")
+				proxywasm.ReplaceHttpResponseHeader(":status", configReplaceStatuscode)
+				for _, item_header := range config.set_header {
+					item_header.ForEach(func(key, value gjson.Result) bool {
+						err := proxywasm.ReplaceHttpResponseHeader(key.String(), value.String())
+						if err != nil {
+							log.Critical("failed ReplaceHttpResponseHeader" + item_header.String())
+						}
+						return true
+					})
+				}
+				// goto func onHttpResponseBody
+				return types.ActionContinue
+			} else {
+				dontReadResponseBody = true
+				break
+			}
+		default:
+			// There is no matching rule
+			dontReadResponseBody = true
+		}
+	}
+
+	// If there is no rule match or no header for x-envoy-upstream-service-time, the onHttpResponseBody is not exec
+	if dontReadResponseBody == true {
+		ctx.DontReadResponseBody()
+	}
+	return types.ActionContinue
+}
+
+func onHttpResponseBody(ctx wrapper.HttpContext, config MyConfig, body []byte, log wrapper.Log) types.Action {
+	bodyStr := string(body)
+
+	for _, item := range config.rules {
+		configMatchResponsebody := item.Get("match.responsebody").String()
+		configReplaceResponsebody := item.Get("replace.responsebody").String()
+		if bodyStr == configMatchResponsebody {
+			proxywasm.ReplaceHttpResponseBody([]byte(configReplaceResponsebody))
+			return types.ActionContinue
+		}
+	}
+
+	return types.ActionContinue
+}