我非要把这个bug优雅的解决掉 | k8s记录events报错：Could not construct referenc

偏执的太偏执、 2023-06-13 04:48 11阅读 0赞

> 作者：小碗汤，一位热爱、认真写作的小伙，目前维护原创公众号：『我的小碗汤』，专注于写golang、docker、kubernetes等知识等提升硬实力的文章，期待你的关注。转载说明：务必注明来源（注明：来源于公众号：我的小碗汤， 作者：小碗汤）

之前写过[手把手教你编写一个控制器][Link 1]，以及[自定义代码生成][Link 2]，记录了编写redis-operator的过程，达到自动操作redis集群，达到自动化运维的目的。

最近搞正在搞给redis operator加记录events事件功能时，报错了（可以说每次加功能都没有顺顺利利的，但这又如何，奈何它也挡不住洒家探索的脚步）报错如下：

Could not construct reference to ***due to: ‘no kind is registered for the type *** in scheme... ’

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9saWFiaW8uYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70]  
记录事件events代码如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9saWFiaW8uYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 1]  
可以一路跟踪代码到client-go/tools/reference/ref.go中：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9saWFiaW8uYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 2]

可以看到45行，其实强转为v1.ObjectReference，也是不会报错的。所以我们可以构建如下的结构体：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9saWFiaW8uYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 3]  
代码像这样子：

ref := &v1.ObjectReference{ 
    			APIVersion: controllerKind.Group + "/" + controllerKind.Version,
    			Kind: controllerKind.Kind,
    			Name: redisCluster.Name,
    			Namespace: redisCluster.Namespace,
    			UID:redisCluster.UID,
    			ResourceVersion: redisCluster.ResourceVersion,
    		}
    rco.eventRecorder.Eventf(ref, v1.EventTypeNormal, "CreateCluster", "create cluster start")

但每次记录events前，都写这么一坨，显然是逼格很低的，况且纵观k8s源码，到处都是直接传pod、svc等内置类型（其实现了runtime.Object），随手一找就看到下面这个样子，将&svc直接传入，优雅很多。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9saWFiaW8uYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 4]

那么该怎么搞才能直接把redisCluster结构体传进去不报错呢？我们先分析下面的源码：

// GetReference returns an ObjectReference which refers to the given
    // object, or an error if the object doesn't follow the conventions
    // that would allow this.
    // TODO: should take a meta.Interface see http://issue.k8s.io/7127
    func GetReference(scheme *runtime.Scheme, obj runtime.Object) (*v1.ObjectReference, error) { 
    	if obj == nil { 
    		return nil, ErrNilObject
    	}
    	if ref, ok := obj.(*v1.ObjectReference); ok { 
    		// Don't make a reference to a reference.
    		return ref, nil
    	}
    
    	gvk := obj.GetObjectKind().GroupVersionKind()
    
    	// if the object referenced is actually persisted, we can just get kind from meta
    	// if we are building an object reference to something not yet persisted, we should fallback to scheme
    	kind := gvk.Kind
    	if len(kind) == 0 { 
    		// TODO: this is wrong
    		gvks, _, err := scheme.ObjectKinds(obj)
    		if err != nil { 
    			return nil, err
    		}
    		kind = gvks[0].Kind
    	}
    
    	// An object that implements only List has enough metadata to build a reference
    	var listMeta metav1.Common
    	objectMeta, err := meta.Accessor(obj)
    	if err != nil { 
    		listMeta, err = meta.CommonAccessor(obj)
    		if err != nil { 
    			return nil, err
    		}
    	} else { 
    		listMeta = objectMeta
    	}
    
    	// if the object referenced is actually persisted, we can also get version from meta
    	version := gvk.GroupVersion().String()
    	if len(version) == 0 { 
    		selfLink := listMeta.GetSelfLink()
    		if len(selfLink) == 0 { 
    			return nil, ErrNoSelfLink
    		}
    		selfLinkUrl, err := url.Parse(selfLink)
    		if err != nil { 
    			return nil, err
    		}
    		// example paths: /<prefix>/<version>/*
    		parts := strings.Split(selfLinkUrl.Path, "/")
    		if len(parts) < 4 { 
    			return nil, fmt.Errorf("unexpected self link format: '%v'; got version '%v'", selfLink, version)
    		}
    		if parts[1] == "api" { 
    			version = parts[2]
    		} else { 
    			version = parts[2] + "/" + parts[3]
    		}
    	}
    
    	// only has list metadata
    	if objectMeta == nil { 
    		return &v1.ObjectReference{ 
    			Kind:            kind,
    			APIVersion:      version,
    			ResourceVersion: listMeta.GetResourceVersion(),
    		}, nil
    	}
    
    	return &v1.ObjectReference{ 
    		Kind:            kind,
    		APIVersion:      version,
    		Name:            objectMeta.GetName(),
    		Namespace:       objectMeta.GetNamespace(),
    		UID:             objectMeta.GetUID(),
    		ResourceVersion: objectMeta.GetResourceVersion(),
    	}, nil
    }

看到最后其实会帮助我们构造v1.ObjectReference对象，但前提是能正确获取到从传入CRD的objectMeta、kind、version，一开始的报错就是因为`scheme.ObjectKinds(obj)`获取kind时返回error导致。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9saWFiaW8uYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 5]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9saWFiaW8uYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 6]  
怎么才能正确获取到kind、version、objectMeta呢？可以查看官方提供的sample-controller，这也是最简单的通过CRD扩展的控制器示例：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9saWFiaW8uYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 7]

// Create event broadcaster
    // Add sample-controller types to the default Kubernetes Scheme so Events can be
    // logged for sample-controller types.
    utilruntime.Must(samplescheme.AddToScheme(scheme.Scheme))

> 创建事件广播器，将样本控制器类型添加到默认的Kubernetes方案，以便可以记录事件以获取样本控制器类型。

`samplescheme.AddToScheme(scheme.Scheme)`会去注册一些GroupVersion、kind等信息到Scheme，这样在记录events时才可以正确获取到。  
对应到我们的CRD，redisCluster对象，就应该是

utilruntime.Must(redisscheme.AddToScheme(scheme.Scheme))

这里的redisscheme是指向code-generator生成的clientset包下的versioned/scheme，register.go中  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9saWFiaW8uYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 8]  
根据golang代码执行顺序可知，被调用时，init函数会被执行，从而调用`v1.AddToGroupVersion`进行注册流程：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9saWFiaW8uYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 9]  
这样分析，顺便把代码修改一番后，重新调试，可以看到正确记录了events事件：![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9saWFiaW8uYmxvZy5jc2RuLm5ldA_size_16_color_FFFFFF_t_70 10]

# 作者简洁 #

[Link 1]: https://liabio.blog.csdn.net/article/details/93619646
[Link 2]: https://liabio.blog.csdn.net/article/details/93620155
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