盤點Serverless架構的六個特質

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"作者 | Wisen Tanasa"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"編譯 | 劉雅夢"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"策劃 | 辛曉亮"}]},{"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","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"本文介紹了Serverless（無服務器）架構的六個特質（Traits）：入門門檻低（Low barrier-to-entry）、無主機（Hostless）、無狀態（Stateless）、彈性（Elasticity）、分佈式（Distributed）和事件驅動（Event-driven）。其目的是倡導大家儘可能廣泛地採用Serverless架構。Serverless架構帶來了一個有趣的範式轉變，這使得軟件開發的許多方面都變得更好了。但它也帶來了技術人員必須要適應的新挑戰。對於如何應對每種特質所帶來的挑戰，我也給出一些簡短的建議，希望這些挑戰不會阻止大家採用Serverless架構。"}]},{"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","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"每當新技術出現時，技術專家的首要任務就是要理解採用新技術的意義。Serverless（無服務器）架構就是一個很好的例子。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"不幸的是，目前關於Serverless架構的文獻大多都只關注於它的優點。許多文章（以及使用示例）都是由雲供應商推出的，因此，會毫不意外地談論其積極方面。本文的意圖是讓大家更好地理解Serverless架構的特質。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"我特意選了特質（Trait）這個詞，而不是特性（Characteristic），因爲這些是Serverless架構的元素，我們無法更改它們。Characteristic特性是可塑的，而Trait特質是固有的。Trait特質也是中性的，因此它既不是積極的也不是消極的。在某些情況下，我所描述的某些類型的Trait特質可能具有積極的含義，但我會保持中立的態度，以便你瞭解自己將要面對的是什麼。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"Trait特質也是內在的，因此你必須要接受它們，而不是與之抗爭，因爲這樣嘗試的話可能會付出相當大的代價。另一方面， Characteristic特性需要花費精力去塑造它們，然而你還是可能會把它們搞錯。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"我還應該向大家介紹Mike Roberts的這篇文章，他也探討了"},{"type":"link","attrs":{"href":"https:\/\/blog.symphonia.io\/defining-serverless-part-1-704d72bc8a32","title":null,"type":null},"content":[{"type":"text","text":"Serverless服務"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"的Traits特質。儘管我們在這裏使用了相同的術語，但值得注意的是，本文所研究的是架構的Traits特質，而不是你所使用的服務的Traits特質。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"本文的目的不是幫助你深入理解所有的主題，而是爲你提供一個大致的概述。以下是本文中定義的Serverless架構的Traits特質："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"numberedlist","attrs":{"start":null,"normalizeStart":1},"content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"入門門檻低（Low barrier-to-entry）"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"無主機（Hostless）"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":3,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"無狀態（Stateless）"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":4,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"彈性（Elasticity）"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":5,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"分佈式（Distributed）"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":6,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"事件驅動（Event-driven）"}]}]}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"入門門檻低"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"讓你的代碼開始在Serverless架構中運行相對來說是簡單的。你可以參照任何教程來開始，並讓代碼在生產級生態系統中運行。在許多方面，Serverless架構的學習曲線並沒有典型的"},{"type":"link","attrs":{"href":"https:\/\/github.com\/kamranahmedse\/developer-roadmap#-devops-roadmap","title":null,"type":null},"content":[{"type":"text","text":"DevOps技能"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"那麼令人生畏——當你使用Serverless架構時，DevOps的許多元素就都是不必要的了。例如，你不必學習服務器管理技能，如配置管理或補丁。這就是爲什麼入門門檻低是Serverless架構的Traits特質之一。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"這意味着，最初開發人員的學習曲線比許多其他架構風格的曲線都要低。但這並不意味着學習曲線會一直保持在較低的水平，事實上，隨着開發人員繼續他們的旅程，整體學習曲線將會變得更陡峭。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"由於這種架構特質，我看到許多新的開發人員很快就加入到了項目中，並且他們能夠有效地爲項目做出貢獻。開發人員能夠快速上手，這可能是Serverless項目能"},{"type":"link","attrs":{"href":"https:\/\/hackernoon.com\/serverless-survey-77-delivery-speed-4-dev-workdays-mo-saved-26-aws-monthly-bill-d99174f70663","title":null,"type":null},"content":[{"type":"text","text":"更快"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"link","attrs":{"href":"https:\/\/hackernoon.com\/serverless-survey-77-delivery-speed-4-dev-workdays-mo-saved-26-aws-monthly-bill-d99174f70663","title":null,"type":null},"content":[{"type":"text","text":"上手"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"link","attrs":{"href":"https:\/\/hackernoon.com\/serverless-survey-77-delivery-speed-4-dev-workdays-mo-saved-26-aws-monthly-bill-d99174f70663","title":null,"type":null},"content":[{"type":"text","text":"的原因之一"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"正如我們所指出的那樣，事情確實會變得更加複雜。例如，基礎設施即代碼（Infrastructure as a code，Iac）、日誌管理、監控，有時還包括網絡，這些仍然都是必不可少的。你必須要瞭解如何在Serverless的世界中實現它們。如果你來自不同的開發背景，那麼你需要了解一些Serverless架構的Traits特質（本文將介紹這些Traits特質）。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"儘管最初的入門門檻很低，但開發人員不應該認爲他們可以忽略重要的架構原則。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"我注意到，一些開發人員傾向於認爲Serverless架構意味着他們不必考慮代碼設計。理由是他們只是在處理函數，所以代碼設計是無關緊要的。事實上，像SOLID這樣的設計原則仍然適用——你不能將代碼的可維護性外包給你的Serverless平臺。儘管你可以將代碼打包並上傳到雲上運行，但我強烈建議你不要這樣做，因爲持續交付實踐在Serverless架構中仍然是相關的。"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"無主機"}]},{"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","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"Serverless架構的一個明顯特質是，你無需直接處理服務器。在這個時代，你可以在各種各樣的主機上安裝並運行服務——無論是物理機、虛擬機、容器等等——用一個詞來描述這一點是很有用的。爲了避免使用已經使用過的術語“無服務器”（“serverless”），我將在這裏使用“主機”（“host”，術語“主機”在"},{"type":"link","attrs":{"href":"https:\/\/www.thoughtworks.com\/books\/building-microservices","title":null,"type":null},"content":[{"type":"text","text":"《構建微服務》"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"一書中使用過）這個詞，因此該Trait特質名爲“無主機”（Hostless）。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"無主機的一個優勢是，你在服務器維護方面的操作開銷將會大大減少。你無需再爲升級服務器而憂心，安全補丁將自動爲你執行。無主機還意味着在應用程序中你需要監控的度量指標也會不同。這是因爲你使用的大多數底層服務不會再發布CPU、內存、磁盤大小等傳統度量指標了。這意味着你不再需要理解架構的低級操作細節。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"但不同的監控指標意味着，你必須重新學習如何調整你的架構。AWS DynamoDB提供了可以供你進行監控和調控的讀寫能力，這是一個你必須要瞭解的概念，而且這種學習是不能遷移到其他Serverless平臺的。你使用的每項服務都有其侷限性。AWS Lambda具有併發執行的限制，你所擁有的CPU核數不存在限制。更奇怪的是，更改Lambda的內存分配大小將會更改獲得的CPU核數。如果你爲了性能測試和生產環境共享一個AWS帳戶，那麼如果性能測試意外地消耗了你的全部併發執行限制，可能會導致生產的宕機。AWS很好地記錄了每項服務的限制，因此請務必檢查它們，以便做出正確的架構決策。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"一個常見的誤解是，Serverless應用程序更安全，因爲安全補丁會自動應用於你的底層服務器。這個假設很危險。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"由於Serverless架構具有不同的攻擊向量，傳統的安全防護已不再適用。應用程序的安全實踐仍然適用，並且在代碼中存儲祕密仍然是一個很大的禁忌。AWS在其"},{"type":"link","attrs":{"href":"https:\/\/aws.amazon.com\/compliance\/shared-responsibility-model\/","title":null,"type":null},"content":[{"type":"text","text":"責任共擔模式"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"中概述了這一點，例如，如果數據包含敏感信息，你仍然需要保護數據。我強烈建議你閱讀"},{"type":"link","attrs":{"href":"https:\/\/www.owasp.org\/index.php\/OWASP_Serverless_Top_10_Project","title":null,"type":null},"content":[{"type":"text","text":"10大OWASP Serverless項目"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"以獲得更多有關該主題的見解。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"雖然你的運維操作開銷大大減少了，但值得注意的是，在極少數情況下，你仍然需要管理底層服務器更改後的影響。你的應用程序可能依賴於原生庫，並且你需要確保在升級基礎操作系統時它們仍可以工作。例如，在AWS Lambda中，"},{"type":"link","attrs":{"href":"https:\/\/aws.amazon.com\/blogs\/compute\/upcoming-updates-to-the-aws-lambda-execution-environment\/","title":null,"type":null},"content":[{"type":"text","text":"操作系統最近已升級到了"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"AMI 2018.03。"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"無狀態"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"函數即服務，即FaaS，是很短暫的，因此你不能在內存中存儲任何內容，因爲運行代碼的計算容器將由平臺自動創建和銷燬。因此，無狀態（Stateless）是Serverless架構中的一個Trait特質。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"無狀態是水平擴展應用程序的一個很好的特質。無狀態的概念是鼓勵你在應用程序中不要存儲狀態。通過不在應用程序中存儲狀態，你將能夠啓動更多的實例，而無需擔心應用程序的狀態，從而實現水平擴展。我在這裏發現了一個有趣的點，實際上無狀態是被迫的，因此錯誤的空間大大減少了。是的，這裏有一些注意事項：例如，計算容器可能會被重複使用，你可以存儲狀態，但是如果你採用這種方法，請務必謹慎處理。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"就應用程序開發而言，你將無法使用需要狀態的技術，因爲狀態管理的負擔是強加給調用方的。例如，不能使用HTTP會話，因爲你沒有具有持久化文件存儲的傳統Web服務器。如果你想使用WebSockets等需要狀態的技術，那麼你需要等待，"},{"type":"link","attrs":{"href":"https:\/\/serverless.com\/blog\/api-gateway-websockets-support\/","title":null,"type":null},"content":[{"type":"text","text":"等到相應的後端即服務（BaaS）支持這些技術爲止"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"，或者應用你自己的解決方案。"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"彈性"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"由於你的架構是無主機的，那麼你的架構也將具有彈性的特質。 你使用的大多數Serverless服務都被設計爲具有高彈性，你可以從零擴展到允許的最大值，然後再回到零，大部分是自動管理的。 彈性是Serverless架構的一個Trait特質。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"對於可擴展性來說，彈性的好處是巨大的。這意味着你不必手動管理資源擴展。資源分配的許多挑戰都消失了。在某些情況下，具有彈性可能只意味着你只需爲所使用的內容付費，因此，如果你的使用模式較低，則可以降低運行成本。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"你可能需要將Serverless架構與不支持這種彈性的遺留系統集成。當這種情況發生時，你可能會破壞下游系統，因爲它們可能無法像Serverless架構那樣擴展。如果你的下游系統是關鍵系統，那麼考慮如何緩解此問題是至關重要的——可能是通過限制AWS Lambda的併發性或利用隊列與下游系統對話。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"雖然在這種高彈性的情況下，“拒絕服務”攻擊（denial of service，DOS）將會變得更加困難，反而更容易受到“拒絕錢包”（denial of wallet）攻擊。在這種情況下，攻擊者試圖通過強制增加資源分配來迫使你超出雲帳戶的限制，從而破壞應用程序。爲了防止這種攻擊，你可能會發現在你的應用程序中使用DDoS保護（如AWS Shield）是很有幫助的。在AWS中，設置AWS預算也很有用，這樣當你的雲賬單暴漲時，你就會收到通知。如果高彈性不是你所期望的，那麼在應用程序上設置約束是很有用的，比如通過限制AWS Lambda併發性。"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"分佈式"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"由於無狀態計算是一種特質，所有的持久性需求都將存儲在後端即服務（BaaS）中，通常是BaaS的組合中。一旦你更多地使用FaaS，你還會發現你的部署單元（即函數）比你已習慣了的可能還要小。因此，在默認情況下，Serverless架構是分佈式的，並且有許多組件必須要通過網絡來進行集成。你的架構還將包括將服務連接在一起，比如身份驗證、數據庫、分佈式隊列等。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"分佈式系統有很多好處，比如我們前面討論過的彈性。在默認情況下，分佈式還能爲你的架構帶來了單區域的高可用性。在Serverless環境中，當雲供應商所在區域的某個可用性區域出現故障時，你的架構將能夠利用其他仍在運行的可用性區域——從開發人員的角度來看，所有這些都是不透明的。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"在選擇架構時總要權衡利弊。在這個特質中，你犧牲了一致性來換取可用性。通常在雲上，每個Serverless服務也都有自己的一致性模型。例如，在AWS S3中，通過在S3桶中對新對象的PUT操作可以獲得“寫後讀”（read-after-write）的一致性。對於對象更新，S3是最終一致的。對於你來說，決定使用哪種BaaS是很常見的，因此要注意它們的一致性模型的行爲。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"另一個挑戰是你需要熟悉分佈式消息的傳遞方法。例如，你需要熟悉並瞭解"},{"type":"link","attrs":{"href":"https:\/\/martinfowler.com\/bliki\/TwoHardThings.html","title":null,"type":null},"content":[{"type":"text","text":"精確一次投遞（exactly-once delivery）"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"這一難題，因爲分佈式隊列的常見消息投遞方式是至少一次投遞（at-least-once-delivery）。由於這種投遞方式，AWS Lambda可以被多次調用，因此你必須確保你的實現是冪等的（瞭解FaaS的重試行爲也很重要，其中AWS Lambda可能會在失敗時多次執行）。你需要了解的其他挑戰還包括分佈式事務的行爲。然而，隨着微服務的普及，構建分佈式系統的學習資源一直在演進。"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"事件驅動"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"Serverless平臺提供的許多BaaS自然會支持事件。對於第三方服務來說，這是一個很好的策略，它們可以爲其用戶提供可擴展性，因爲你無法控制他們服務的代碼。由於你將在Serverless架構中使用大量的BaaS，因此你的架構是具有事件驅動這一Trait特質的。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"我還認識到，即使你的架構是具有事件驅動這一Trait特質的，但這並不意味着你需要完全採用事件驅動的架構。然而，我觀察到，當將事件驅動架構自然地提供給團隊時，團隊更傾向於接受它。這個特質和彈性特質類似，不需要時，你仍然可以關閉它。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"事件驅動能帶來很多好處。架構組件之間的耦合程度很低。在Serverless架構中，你可以很容易地引入一個新函數來監聽blob存儲中的更改："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"image","attrs":{"src":"https:\/\/static001.geekbang.org\/infoq\/bd\/bdcc7701cd7389be560217a26925ae36.png","alt":null,"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},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 注意，當添加函數B時，函數A並沒有改變（參見圖1）。這增加了函數的內聚性。函數具有高內聚是有很多好處的，其中一個好處是當單個操作失敗時，你可以輕鬆地重試該操作。當函數B失敗重試時，意味着你不需要運行高昂的函數A。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"特別是在雲計算中，雲供應商將確保你的FaaS與他們的BaaS能夠輕鬆集成。FaaS可以被設計成由"},{"type":"link","attrs":{"href":"https:\/\/martinfowler.com\/articles\/201701-event-driven.html","title":null,"type":null},"content":[{"type":"text","text":"事件通知"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"觸發。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"事件驅動架構的缺點是，開始時你可能會失去系統作爲一個整體的整體視圖。這會使得對系統進行故障排除變得更具挑戰性。分佈式跟蹤是你應該研究的一個領域，儘管它在Serverless架構中仍然是一個成熟的領域。AWS X-Ray是一種可以在AWS中開箱即用的服務。X-Ray"},{"type":"link","attrs":{"href":"https:\/\/read.acloud.guru\/im-here-to-tell-you-the-truth-the-good-the-bad-and-the-ugly-of-aws-x-ray-and-lambda-f212b5f332e9","title":null,"type":null},"content":[{"type":"text","text":"確實有其自身的侷限性"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"，如果你已經超越了它，你應該關注這個領域，因爲有第三方的產品正在湧現。這就是爲什麼記錄關聯ID（Correlation IDs）的實踐是必不可少的，特別是在事務中使用多個BaaS的情況下。所以一定要確保實現關聯ID。"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"結論"}]},{"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","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"本文介紹了Serverless架構的六個Traits特質：入門門檻低、無主機、無狀態、彈性、分佈式和事件驅動。我的目的是倡導大家儘可能廣泛地採用Serverless架構。Serverless架構帶來了一個有趣的範式轉變，這使得軟件開發的許多方面都變得更好了。但它也帶來了技術人員必須要適應的新挑戰。對於如何應對每種Trait特質所帶來的挑戰，我也給出一些簡短的建議，希望這些挑戰不會阻止你採用Serverless架構。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#222222","name":"user"}},{"type":"strong"}],"text":"原文鏈接："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https:\/\/www.thoughtworks.com\/insights\/blog\/traits-serverless-architecture","title":null,"type":null},"content":[{"type":"text","text":"https:\/\/www.thoughtworks.com\/insights\/blog\/traits-serverless-architecture"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]}]}]}