如何使用 DDD 指導微服務拆分？

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"  ","attrs":{}}]},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"我是架構精進之路，大廠架構師，CSDN博客專家，點擊上方“關注”，堅持每天爲你分享技術乾貨，私信我回復“01”，送你一份程序員成長進階大禮包。  ","attrs":{}}]}],"attrs":{}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"軟件架構發展經歷","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"軟件架構的發展經歷了從單體架構、垂直架構、SOA架構到微服務架構以及到現在最新的service mesh（網格服務架構）的過程。借用dubbo的網站架構發展圖和說明：","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/35/35e443250addbb67ff5b76d2b071f5be.png","alt":"圖片","title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"微服務存在的問題","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"進入微服務之後 ， 解決了集中式架構的單體應用很多問題， 但是新的問題應運而生 ， 微服務的力度應該多大 ？微服務如何設計呢？微服務如何拆分 ？微服務邊界在哪裏 ？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"很長時間人們都沒有解決這一問題，就連Martin Fowler在提出微服務架構的時候也沒有告訴我們這該如何拆分微服務。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"甚至在很長的時間裏人們對微服務拆分產生了一些誤解， 有人認爲：\"微服務很簡單，就是將之前的單體應用拆分成多個部署包， 或者將原來的單體應用架構替換爲一套支持微服務的技術架構，就算是微服務了。\" 還有人認爲微服務應該拆分得越小越好。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"鑑於上述情形， 很多項目因爲前期拆分過度， 導致複雜度過高， 導致後期難以運維甚至難以上線。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"可以得出一個結論：","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"微服務拆分困境產生的根本原因就是不知道業務或者微服務的邊界到底在什麼地方。換句話說，確定了業務邊界和應用邊界，這個困境也就迎刃而解了。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"DDD的誕生","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"而DDD就是解決了這個確定業務邊界的問題，可見DDD並不是一種技術架構，而是一種劃分業務領域範圍的方法論。DDD的興起是由於很多熟悉領域驅動建模(DDD)的工程師在進行微服務設計時， 發現用DDD的思路進行業務梳理可以很好規劃服務邊界， 可以很好實現微服務內部和外部的\"高內聚、低耦合\"。於是越來越多的人將DDD作爲業務劃分的指導思想。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"DDD是一種拆解業務、劃分業務、確定業務邊界的方法， 是一種高度複雜的領域設計思想，將我們的問題拆分成一個個地域， 試圖分離技術實現的複雜性，主要解決的是軟件難以理解難以演進的問題，DDD不是一種架構， 而是一種架構方法論， 目的就是將複雜問題領域簡單化， 幫助我們設計出清晰的領域和邊界， 可以很好的實現技術架構的演進。DDD包括兩部分，戰略設計部分和戰術設計部分。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"戰略設計","attrs":{}},{"type":"text","text":"主要從業務視角出發，建立業務領域模型，劃分領域邊界，建立通用語言的限界上下文，限界上下文可以作爲微服務設計的參考邊界。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"戰術設計","attrs":{}},{"type":"text","text":"則從技術視角出發，側重於領域模型的技術實現，完成軟件開發和落地，包括：聚合根、實體、值對象、領域服務、應用服務和資源庫等代碼邏輯的設計和實現。","attrs":{}}]}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"微服務拆分難題","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"開發者在剛開始嘗試實現自己的微服務架構時，往往會產生一系列問題 ：","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"微服務到底應該怎麼劃分？","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"一個典型的微服務到底應該有多微？","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果做了微服務設計，最後真的會有好處嗎？","attrs":{}}]}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"回答上面的問題需要首先了解微服務設計的邏輯，","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"科學的架構設計應該通過一些輸入並逐步推導出結果","attrs":{}},{"type":"text","text":"，架構師要避免憑空設計和“拍腦門”的做法。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"服務的劃分有一些基本的方法和原則，通過這些方法能讓微服務劃分更有操作性。最終在微服務落地實施時也能按圖索驥，無論是對遺留系統改造還是全新系統的架構都能遊刃有餘。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"微服務拆分的幾個階段","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在開始劃分微服務之前，架構師需要在大腦中有一個重要的認識：","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"微服務只是手段，不是目的。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"微服務架構是爲了讓系統變得更容易拓展、更富有彈性。在把單體應用變成靠譜的微服務架構之前，單體系統的各個模塊應該是合理、清晰地。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"也就是說，從邏輯上單體系統和微服務沒有區別，某種理想情況下微服務只是把單體系統的各個模塊分開部署了而已","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"大量的實踐教訓告訴我們，混沌的微服務架構，比解耦良好的單體應用會帶來更多麻煩。","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/74/74d22309b225f5de1f3d6b949bf5c0eb.webp","alt":null,"title":"混亂的微服務VS良好的單體","style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":"","fromPaste":false,"pastePass":false}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"領域驅動設計立足於面向對象思想，從業務出發，通過領域模型的方式反映系統的抽象，從而得到合理的服務劃分。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"採用 DDD 來進行業務建模和服務拆分時，可以參考下面幾個階段：","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"使用 DDD（領域驅動建模） 進行業務建模，從業務中獲取抽象的模型（例如訂單、用戶），根據模型的關係進行劃分限界上下文。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"檢驗模型是否得到合適的的抽象，並能反映系統設計和響應業務變化。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"從 DDD 的限界上下文往微服務轉化，並得到系統架構、API列表、集成方式等產出。","attrs":{}}]}]}],"attrs":{}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/a5/a50add5987d886392b4ee5765013f97e.webp","alt":null,"title":"使用DDD劃分微服務的過程\n","style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":"","fromPaste":false,"pastePass":false}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"如何抽象？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"抽象需要找到看似無關事務的內在聯繫，對微服務的設計尤爲重要。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"然而現實的例子比比皆是，電信或移動營業廳還需要用戶分兩步辦理號卡業務、寬帶業務。原始是不合適的抽象模型造成的，並最終影響了微服務的劃分。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"我們可以使用概念圖來描述一些概念的抽象關係。","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/5e/5ef9169ccceb7d7e2b174fc6bc13df9f.png","alt":null,"title":"商品這一概念的概念圖","style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":"","fromPaste":false,"pastePass":false}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果沒有抽象出領域模型，就得不到正確的微服務劃分。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"使用DDD進行業務建模","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"通過利用DDD對系統從業務的角度分析，對系統進行抽象後，得到內聚更高的業務模型集合，在DDD中一組概念接近、高度內聚並能找到清晰的邊界的業務模型被稱作限界上下文（Bounded Context）。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"限界上下文可以視爲邏輯上的微服務，或者單體應用中的一個組件。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在電商領域就是訂單、商品以及支付等幾個在電商領域最爲常見的概念；在社交領域就是用戶、羣組、消息等。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"DDD的方法論中是如何找到子系統的邊界的呢？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"其中一項實踐叫做事件風暴工作坊，工作坊要求業務需求提出者和技術實施者協作完成領域建模。把系統狀態做出改變的事件作爲關鍵點，從系統事件的角度觸發，提取能反應系統運作的業務模型。再進一步識別模型之間的關係，劃分出限界上下文，可以看做邏輯上的微服務。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"事件是系統數據流中的關鍵點，類似於電影製作中的關鍵幀。","attrs":{}}]},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"例如系統管理員可以登錄、創建商品、上架商品，對應的系統狀態的改變是用戶已登錄、商品已創建、商品已經上架；相應的顧客可以登錄、創建訂單、支付，對應的系統狀態改變是用戶已登錄、訂單已創建、訂單已支付。","attrs":{}}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/91/91eb843aca515d9ea61e3445da62affe.png","alt":null,"title":"利用事件刺探業務黑盒並抽象出模型","style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":"","fromPaste":false,"pastePass":false}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在得到模型之後，通過分析模型之間的關係得出限界上下文。例如商品屬性和商品相對於用戶、用戶組關係更爲密切，通過這些關係作出限界上下文拆分的基本線索。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"其次是識別模型中的二義性，讓限界上下文劃分更爲準確。","attrs":{}}]},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"例如，在電商領域，另外一個不恰當設計的例子是：把訂單中的訂單項當做和商品同樣的概念劃分到了商品服務","attrs":{}}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"但訂單中的商品實際上和商品庫中的商品不是同一個概念。當訂單需要修改訂單下的商品信息時，需要訪問商品服務，這勢必造成了訂單和商品服務的耦合。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"合理的設計應該是：商品服務提供商品的信息給訂單服務，但是訂單服務沒有理由修改商品信息，而是訪問作爲商品快照的訂單項。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"訂單項應該作爲一個獨立的概念被劃分到訂單服務中，而不是和商品使用同一個概念，甚至共享同一張數據庫表。","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/2a/2a12f09bca66ce65e81ed0cf83af39a9.png","alt":null,"title":"典型具有”二義性“陷阱的場景","style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":"","fromPaste":false,"pastePass":false}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"一組關係密切的模型形成了上下文（context），二義性的識別能幫我們找到上下文的邊界（bounded）。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"驗證和評審領域模型","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"前面我們說到限界上下文可以作爲邏輯上的微服務，但並不意味着我們可以直接把限界上下文變成微服務。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"限界上下文被設計出來後，驗證它的方法可以從我們採用微服務的兩個目的出發：降低耦合、容易擴展，可以作爲限界上下文評審原則：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"原則1：","attrs":{}},{"type":"text","text":"設計出來的限界上下文之間的互相依賴應該越少越好，依賴的上游不應該知道下游的信息。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"原則2：","attrs":{}},{"type":"text","text":"使用潛在業務進行適配，如果能在一定程度上響應業務變化，則證明用它指導出來的微服務可以在相當一段時間內足以支撐應用開發。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"但是理想的領域模型往往抽象程度、成本、複用性這幾個因素中獲取平衡。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/9a/9a9a6f639a098621ee2d4667e4fbc02b.webp","alt":null,"title":"”抽象”的成本","style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":"","fromPaste":false,"pastePass":false}},{"type":"paragraph","attrs":{"indent":0,"n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API集成。這種方式讓耦合變得極低，甚至稍作修改就可以暴露給外部系統使用。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這三種集成方式耦合程度由高到低，適用於不同的場景，需要根據實際情況選擇，甚至在系統中可能同時存在。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"服務間集成的方式還有其他方式，一般來說，上面三種微服務集成的方式可以概括目前常見系統大部分需求。","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/ba/bad6ee71d9b02ecfcbb023e0dab092ca.png","alt":"圖片","title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"總結","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這篇文章主要研討了DDD火起來的原因， 解決了什麼業界難題， 知道DDD主要思路 ， 以及DDD大概的實現步驟等 。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"邏輯往往比經驗更爲重要。寫這篇文章的初衷是爲了得到微服務劃分的依據是什麼，我該怎麼有說服力的回覆？","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"是具體情況具體分析？By experience？還是說，我是通過一套方法對業務邏輯進行分析得到的。","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"當沒有足夠的經驗直接解決問題，或問題龐大到不足以使用經驗解決時，能支撐你做出決策就只有對輸入問題進行有效的分析。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"使用 DDD 指導微服務劃分，能在一定程度上彌補經驗的不足，做出有理有據的系統架構設計。","attrs":{}}]}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"我是架構精進之路，大廠架構師，CSDN博客專家，點擊上方“關注”，堅持每天爲你分享技術乾貨，私信我回復“01”，送你一份程序員成長進階大禮包。  ","attrs":{}}]}],"attrs":{}}]}