Knative Func无法连接Broker，curl/busybox可正常访问，求问题排查

问题描述 #

搭建了Knative测试环境（基于全新microk8s，未配置Istio或复杂ServiceAccount），尝试使用Eventing功能：

• default命名空间下的Broker信息如下：

C:\dev\knative-test\functions\register-user>kubectl get broker -n default
NAME          URL
AGE   READY   REASON
user-broker   http://broker-ingress.knative-eventing.svc.cluster.local/default/user-broker
11h   True

• 通过端口转发后，用curl访问Broker URL可成功发送事件并路由到对应Trigger/Subscriber，请求详情：

C:\dev\knative-test\functions\register-user>curl -v http://localhost:80/default/user-broker -X POST -H "Ce-Id: say-hello" -H "Ce-Specversion: 1.0" -H "Ce-Type: greeting" -H "Ce-Source: not-sendoff" -H "Content-Type: application/json" -d '{"msg":"Hello Knative!"}'
Note: Unnecessary use of -X or --request, POST is already inferred.
* Host localhost:80 was resolved.
* IPv6: ::1
* IPv4: 127.0.0.1
*   Trying [::1]:80...
* Connected to localhost (::1) port 80
> POST /default/user-broker HTTP/1.1
> Host: localhost
> User-Agent: curl/8.7.1
> Accept: */*
> Ce-Id: say-hello
> Ce-Specversion: 1.0
> Ce-Type: greeting
> Ce-Source: not-sendoff
> Content-Type: application/json
> Content-Length: 22
>
* upload completely sent off: 22 bytes
< HTTP/1.1 202 Accepted
< Allow: POST, OPTIONS
< Date: Sun, 11 Aug 2024 12:50:26 GMT
< Content-Length: 0
<
* Connection #0 to host localhost left intact

• 但使用Go编写的Knative Func发送事件时，Broker日志报错：

2024-08-11T12:45:10.096628364Z {"level":"warn","ts":"2024-08-11T12:45:10.096Z","logger":"mt_broker_ingress","caller":"ingress/ingress_handler.go:139","msg":"Broker getter failed","commit":"c3baeda"}
2024-08-11T12:45:10.096716467Z {"level":"warn","ts":"2024-08-11T12:45:10.096Z","logger":"mt_broker_ingress","caller":"ingress/ingress_handler.go:230","msg":"Failed to retrieve broker","commit":"c3baeda","error":"broker.eventing.knative.dev \"default\" not found"}

• Go代码如下：

func Handle(w http.ResponseWriter, r *http.Request) {
    ctx := cloudevents.ContextWithTarget(context.Background(), "http://broker-ingress.knative-eventing.svc.cluster.local/default/user-broker")

    p, err := cloudevents.NewHTTP(
        cloudevents.WithTarget("http://broker-ingress.knative-eventing.svc.cluster.local/default/user-broker"),
    )
    if err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return
    }

    c, err := cloudevents.NewClient(p, cloudevents.WithTimeNow(), cloudevents.WithUUIDs())
    if err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return
    }

    // Parse the request body into a User struct.
    var user User
    err = parseBody(r, &user)
    if err != nil {
        http.Error(w, err.Error(), http.StatusBadRequest)
        return
    }

    // Create a new event using cloudevents
    event := cloudevents.NewEvent()
    event.SetID(uuid.New().String())
    event.SetSource("fanfuse/functions/register-user")
    event.SetType("fanfuse.user.register")
    if err := event.SetData(cloudevents.ApplicationJSON, user); err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return
    }

    // Send the event
    if result := c.Send(ctx, event); !cloudevents.IsACK(result) {
        log.Printf("Failed to send event to broker: %v", result)
        http.Error(w, fmt.Sprintf("failed to send event: %v", result), http.StatusInternalServerError)
        return
    } else {
        log.Printf("Event sent successfully: \n%s\n", event)
    }
}

已确认Broker正常、DNS解析正常、URL配置正确，排查问题原因及解决方法。

解决方案 #

问题出在Go代码创建的CloudEvents版本不兼容：

• curl请求明确指定了Ce-Specversion: 1.0，而你的Go代码中event := cloudevents.NewEvent()默认创建的是CloudEvents 0.3版本（specversion: 0.3）。
• Knative Eventing的Broker Ingress对CloudEvents 1.0有强依赖，版本不匹配会导致Ingress无法正确解析请求路径中的Broker名称（user-broker），进而 fallback 尝试查找名为default的Broker，最终触发broker.eventing.knative.dev "default" not found错误。

修复步骤 #

修改Go代码中创建Event的逻辑，明确指定使用CloudEvents 1.0版本：

// 将原来的 event := cloudevents.NewEvent() 修改为：
event := cloudevents.NewEvent(cloudevents.VersionV1)

或者在创建Event后手动设置版本：

event := cloudevents.NewEvent()
event.SetSpecVersion(cloudevents.VersionV1) // 添加这一行

验证要点 #

• 修复后，代码发送的事件会携带Ce-Specversion: 1.0头，与curl请求格式一致。
• Broker Ingress可正确解析路径中的default命名空间和user-broker实例，事件能正常路由到对应的Trigger。

内容的提问来源于stack exchange，提问作者Andy Troschke