Add wasm plugin contribution introduction (#47)

plugins/wasm-go/extensions/http-call/main.go

@@ -0,0 +1,120 @@
+// Copyright (c) 2022 Alibaba Group Holding Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"errors"
+	"net/http"
+	"strings"
+
+	"github.com/tetratelabs/proxy-wasm-go-sdk/proxywasm"
+	"github.com/tetratelabs/proxy-wasm-go-sdk/proxywasm/types"
+	"github.com/tidwall/gjson"
+
+	"github.com/alibaba/higress/plugins/wasm-go/pkg/wrapper"
+)
+
+func main() {
+	wrapper.SetCtx(
+		"http-call",
+		wrapper.ParseConfigBy(parseConfig),
+		wrapper.ProcessRequestHeadersBy(onHttpRequestHeaders),
+	)
+}
+
+type HttpCallConfig struct {
+	client      wrapper.HttpClient
+	requestPath string
+	bodyHeader  string
+	tokenHeader string
+}
+
+func parseConfig(json gjson.Result, config *HttpCallConfig, log wrapper.LogWrapper) error {
+	config.bodyHeader = json.Get("bodyHeader").String()
+	if config.bodyHeader == "" {
+		return errors.New("missing bodyHeader in config")
+	}
+	config.tokenHeader = json.Get("tokenHeader").String()
+	if config.tokenHeader == "" {
+		return errors.New("missing tokenHeader in config")
+	}
+	config.requestPath = json.Get("requestPath").String()
+	if config.requestPath == "" {
+		return errors.New("missing requestPath in config")
+	}
+	serviceSource := json.Get("serviceSource").String()
+	serviceName := json.Get("serviceName").String()
+	servicePort := json.Get("servicePort").Int()
+	if serviceName == "" || servicePort == 0 {
+		return errors.New("invalid service config")
+	}
+	switch serviceSource {
+	case "k8s":
+		namespace := json.Get("namespace").String()
+		config.client = wrapper.NewClusterClient(wrapper.K8sCluster{
+			ServiceName: serviceName,
+			Namespace:   namespace,
+			Port:        servicePort,
+		})
+		return nil
+	case "nacos":
+		namespace := json.Get("namespace").String()
+		config.client = wrapper.NewClusterClient(wrapper.NacosCluster{
+			ServiceName: serviceName,
+			NamespaceID: namespace,
+			Port:        servicePort,
+		})
+		return nil
+	case "ip":
+		config.client = wrapper.NewClusterClient(wrapper.StaticIpCluster{
+			ServiceName: serviceName,
+			Port:        servicePort,
+		})
+		return nil
+	case "dns":
+		domain := json.Get("domain").String()
+		config.client = wrapper.NewClusterClient(wrapper.DnsCluster{
+			ServiceName: serviceName,
+			Port:        servicePort,
+			Domain:      domain,
+		})
+		return nil
+	default:
+		return errors.New("unknown service source: " + serviceSource)
+	}
+}
+
+func onHttpRequestHeaders(ctx *wrapper.CommonHttpCtx[HttpCallConfig], config HttpCallConfig, needBody *bool, log wrapper.LogWrapper) types.Action {
+	config.client.Get(config.requestPath, nil,
+		func(statusCode int, responseHeaders http.Header, responseBody []byte) {
+			defer proxywasm.ResumeHttpRequest()
+			if statusCode != http.StatusOK {
+				log.Errorf("http call failed, status: %d", statusCode)
+				proxywasm.SendHttpResponse(http.StatusInternalServerError, nil,
+					[]byte("http call failed"), -1)
+				return
+			}
+			// avoid protocol error
+			body := strings.ReplaceAll(string(responseBody), "\n", "#")
+			// set body to the original request header
+			proxywasm.AddHttpRequestHeader(config.bodyHeader, body)
+			// set service response token header to the original request header
+			token := responseHeaders.Get(config.tokenHeader)
+			if token != "" {
+				proxywasm.AddHttpRequestHeader(config.tokenHeader, token)
+			}
+		})
+	return types.ActionPause
+}