add example for extending span attributes (#1936)

plugins/wasm-go/examples/custom-span-attribute/go.mod

@@ -0,0 +1,20 @@
+module github.com/alibaba/higress/plugins/wasm-go/extensions/custom-logs
+
+go 1.18
+
+replace github.com/alibaba/higress/plugins/wasm-go => ../..
+
+require (
+	github.com/alibaba/higress/plugins/wasm-go v0.0.0
+	github.com/higress-group/proxy-wasm-go-sdk v1.0.0
+)
+
+require (
+	github.com/google/uuid v1.3.0 // indirect
+	github.com/higress-group/nottinygc v0.0.0-20231101025119-e93c4c2f8520 // indirect
+	github.com/magefile/mage v1.14.0 // indirect
+	github.com/tidwall/gjson v1.17.3 // indirect
+	github.com/tidwall/match v1.1.1 // indirect
+	github.com/tidwall/pretty v1.2.0 // indirect
+	github.com/tidwall/resp v0.1.1 // indirect
+)

plugins/wasm-go/examples/custom-span-attribute/go.sum

@@ -0,0 +1,20 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/google/uuid v1.3.0 h1:t6JiXgmwXMjEs8VusXIJk2BXHsn+wx8BZdTaoZ5fu7I=
+github.com/google/uuid v1.3.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/higress-group/nottinygc v0.0.0-20231101025119-e93c4c2f8520 h1:IHDghbGQ2DTIXHBHxWfqCYQW1fKjyJ/I7W1pMyUDeEA=
+github.com/higress-group/nottinygc v0.0.0-20231101025119-e93c4c2f8520/go.mod h1:Nz8ORLaFiLWotg6GeKlJMhv8cci8mM43uEnLA5t8iew=
+github.com/higress-group/proxy-wasm-go-sdk v1.0.0 h1:BZRNf4R7jr9hwRivg/E29nkVaKEak5MWjBDhWjuHijU=
+github.com/higress-group/proxy-wasm-go-sdk v1.0.0/go.mod h1:iiSyFbo+rAtbtGt/bsefv8GU57h9CCLYGJA74/tF5/0=
+github.com/magefile/mage v1.14.0 h1:6QDX3g6z1YvJ4olPhT1wksUcSa/V0a1B+pJb73fBjyo=
+github.com/magefile/mage v1.14.0/go.mod h1:z5UZb/iS3GoOSn0JgWuiw7dxlurVYTu+/jHXqQg881A=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
+github.com/tidwall/gjson v1.17.3 h1:bwWLZU7icoKRG+C+0PNwIKC6FCJO/Q3p2pZvuP0jN94=
+github.com/tidwall/gjson v1.17.3/go.mod h1:/wbyibRr2FHMks5tjHJ5F8dMZh3AcwJEMf5vlfC0lxk=
+github.com/tidwall/match v1.1.1 h1:+Ho715JplO36QYgwN9PGYNhgZvoUSc9X2c80KVTi+GA=
+github.com/tidwall/match v1.1.1/go.mod h1:eRSPERbgtNPcGhD8UCthc6PmLEQXEWd3PRB5JTxsfmM=
+github.com/tidwall/pretty v1.2.0 h1:RWIZEg2iJ8/g6fDDYzMpobmaoGh5OLl4AXtGUGPcqCs=
+github.com/tidwall/pretty v1.2.0/go.mod h1:ITEVvHYasfjBbM0u2Pg8T2nJnzm8xPwvNhhsoaGGjNU=
+github.com/tidwall/resp v0.1.1 h1:Ly20wkhqKTmDUPlyM1S7pWo5kk0tDu8OoC/vFArXmwE=
+github.com/tidwall/resp v0.1.1/go.mod h1:3/FrruOBAxPTPtundW0VXgmsQ4ZBA0Aw714lVYgwFa0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

plugins/wasm-go/examples/custom-span-attribute/main.go

@@ -0,0 +1,70 @@
+// 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"
+	"fmt"
+
+	"github.com/higress-group/proxy-wasm-go-sdk/proxywasm"
+	"github.com/higress-group/proxy-wasm-go-sdk/proxywasm/types"
+	"github.com/tidwall/gjson"
+
+	"github.com/alibaba/higress/plugins/wasm-go/pkg/wrapper"
+)
+
+func main() {
+	wrapper.SetCtx(
+		"custom-span-attribute",
+		wrapper.ParseConfigBy(parseConfig),
+		wrapper.ProcessRequestHeadersBy(onHttpRequestHeaders),
+	)
+}
+
+type CustomSpanAttributeConfig struct {
+	HeaderKey string
+}
+
+func setSpanAttribute(key string, value interface{}, log wrapper.Log) {
+	if value != "" {
+		traceSpanTag := wrapper.TraceSpanTagPrefix + key
+		if e := proxywasm.SetProperty([]string{traceSpanTag}, []byte(fmt.Sprint(value))); e != nil {
+			log.Warnf("failed to set %s in filter state: %v", traceSpanTag, e)
+		}
+	} else {
+		log.Debugf("failed to write span attribute [%s], because it's value is empty")
+	}
+}
+
+/*
+Example configuration:
+
+```yaml
+headerKey: foo
+```
+*/
+func parseConfig(configJson gjson.Result, config *CustomSpanAttributeConfig, log wrapper.Log) error {
+	config.HeaderKey = configJson.Get("headerKey").String()
+	if config.HeaderKey == "" {
+		return errors.New("no header key specified")
+	}
+	return nil
+}
+
+func onHttpRequestHeaders(ctx wrapper.HttpContext, config CustomSpanAttributeConfig, log wrapper.Log) types.Action {
+	headerValue, _ := proxywasm.GetHttpRequestHeader(config.HeaderKey)
+	setSpanAttribute(config.HeaderKey, headerValue, log)
+	return types.ActionContinue
+}