避免不完全的雲原生（六）：爲什麼你可能不需要彈性伸縮？

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"italic"},{"type":"color","attrs":{"color":"#333333","name":"user"}},{"type":"strong"}],"text":"本文最初發佈於The Startup博客，經原作者授權由InfoQ中文站翻譯並分享。"}]},{"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":"雲原生開發最常見的其中一個特性是彈性伸縮。許多公司告訴我們，他們認爲彈性伸縮是他們的團隊評估雲平臺的關鍵需求。然而，我們很少聽到這些團隊告訴我們，他們爲什麼需要彈性伸縮。"}]},{"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":"事實上，我們甚至可以說彈性伸縮是“在雲上”的標誌之一。所有云平臺都提供某種彈性伸縮支持。不管是Kubernetes中的"},{"type":"link","attrs":{"href":"https:\/\/kubernetes.io\/docs\/tasks\/run-application\/horizontal-pod-autoscale\/","title":null,"type":null},"content":[{"type":"text","text":"Horizontal Pod Autoscalers"}]},{"type":"text","text":"（根據觀察到的CPU利用率自動擴展Pods的數量），還是像"},{"type":"link","attrs":{"href":"https:\/\/aws.amazon.com\/autoscaling\/","title":null,"type":null},"content":[{"type":"text","text":"AWS Autoscaling"}]},{"type":"text","text":"（它會自動縮放EC2實例、Dynamo DB表和許多其他資源類型）這樣的供應商特性，通常，彈性伸縮都被視爲最想要的雲特性。"}]},{"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":"如果你是一家全新的初創公司，正在構建一個新的B2C應用程序，那麼彈性伸縮可能至關重要，因爲你無法預測你的業務何時會突然騰飛。但大型企業不是初創公司。它們有現有的客戶羣，而且它們的使用模式在很大程度上是已知的。相反，在大多數企業中，我們看到，公司是將所有不同的工作負載作爲一個整體來運行，這些工作負載大致可以分爲以下幾類："}]},{"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":"color","attrs":{"color":"#494949","name":"user"}}],"text":"最大的一類是"},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}},{"type":"strong"}],"text":"靜態負載"},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"，它是可預測的、不變的負載；這可能佔所有應用程序的65%。"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"第二大類是"},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}},{"type":"strong"}],"text":"計劃內的伸縮"},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"（季節性、批量處理或計劃內的活動）——可能佔所有應用程序的35%。"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"剩下的就是"},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}},{"type":"strong"}],"text":"計劃外的伸縮"},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"（不可預測的負載）；剩下的可能非常少——在許多企業，這樣的應用程序可能只有5%。"}]}]}]},{"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":"下圖展示了這個劃分（取自一個真實的客戶，僅用於說明這種情況）："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https:\/\/static001.geekbang.org\/infoq\/3f\/3f1c2eceea7fbf6da09363eb0a4e6079.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":"center","origin":null},"content":[{"type":"text","text":"各種伸縮情況的佔比"}]},{"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":"問題是，許多團隊在構建他們的應用程序時，都將其當成是這5%的一部分，而實際上，只有很少的應用程序屬於這5%，這5%總是受到計劃外負載的影響。現在，這並不是一個新問題。在相對更傳統的應用程序環境中，常見的方法是準備遠超需要的基礎設施，“以防萬一”。顯然，這是一種浪費，也是團隊想要遷移到雲的原因之一。然而，理想的雲原生方法假定每個功能都部署成可無限擴展的。然而，對於我們與之合作的那類大型企業，更好的方法是設法識別這5%的功能，將它們從龐大的單體中分離出來，並以雲原生的方式構建它們（例如，它們可能是Strangler模式的早期候選對象）。"}]},{"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":"因此，假設所有的雲原生程序都必須具有彈性和無限的可伸縮性，通常是一種誤導——相反，對於95%的企業應用程序來說，更重要的是"},{"type":"text","marks":[{"type":"italic"}],"text":"彈性"},{"type":"text","text":"而不是彈性伸縮。反之，如果我們需要的是"},{"type":"text","marks":[{"type":"strong"}],"text":"橫向穩定性"},{"type":"text","text":"（這是實現橫向伸縮的必要條件），那麼，這些程序就是那5%確實需要橫向穩定性的。"}]},{"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":"因此，換句話說，如果一個節點或實例丟失、替換或重啓，程序應該可以繼續穩定地運行，而服務不會中斷——與突然需要額外增加節點的擴展相比，這要常見得多。現在我們發現，關鍵的雲原生要素（如松耦合、不使用共享數據庫以及僅通過HTTP和消息傳遞系統等標準的、可伸縮的協議進行進程間通信）是實現這一目標的好方法。因此，以"},{"type":"link","attrs":{"href":"https:\/\/medium.com\/swlh\/what-does-cloud-native-really-mean-1b10ed003aa9","title":null,"type":null},"content":[{"type":"text","text":"雲原生方式"}]},{"type":"text","text":"編寫應用程序仍然是正確的做法，但原因可能和你想的不同。"}]},{"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":"而且，對於許多企業來說，彈性伸縮都是一種反模式。例如，當我們與一家銀行談論彈性軟件許可模型時，我們被告知，鑑於他們進行應用程序成本規劃的方式，對於新項目的業務案例，他們實際上需要預先確定軟件成本。遺憾的是，我們合作的很多企業都是如此。"}]},{"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":"一個我們會反覆聽說的可怕的故事（太經常了，我們都希望它是虛構的，但不幸的是我們見證了不只一個這樣的例子）是，一個團隊新部署了一個具備自動伸縮能力的雲原生應用程序，第一個月因爲自動伸縮而產生了一個鉅額的雲提供商賬單，這不是因爲客戶使用率高，而是因爲在測試中未遇到的意外錯誤導致在正常負載下CPU利用率反常升高。在成本模型和財務規劃趕上技術發展的步伐之前，你最好以雲原生的方式構建應用程序，但部署的時候要麼固定資源數量，要麼採用有資源限制的自動伸縮設置。"}]},{"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":"查看英文原文："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https:\/\/medium.com\/swlh\/a-cloud-native-coda-why-you-probably-dont-need-elastic-scaling-46b9315df635","title":null,"type":null},"content":[{"type":"text","text":"A Cloud-Native Coda: Why You (probably) Don’t Need Elastic Scaling"}]}]},{"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":"延伸閱讀："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https:\/\/www.infoq.cn\/article\/qff32QZ7iTN5N0MGhq5M","title":"xxx","type":null},"content":[{"type":"text","text":"避免不完全的雲原生（五）：目標和收益"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https:\/\/www.infoq.cn\/article\/Yc8fCIyvIwmBahZ1TPwy","title":"xxx","type":null},"content":[{"type":"text","text":"避免不完全的雲原生（四）：技術和基礎設施角度"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https:\/\/www.infoq.cn\/article\/LmUVC2HHNPD5lHSzETUa","title":"xxx","type":null},"content":[{"type":"text","text":"避免不完全的雲原生（三）：架構和設計角度"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https:\/\/www.infoq.cn\/article\/Qj0SqAEDZZyVOPyhyTXY","title":"","type":null},"content":[{"type":"text","text":"避免不完全的雲原生（二）：人員和流程要素"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https:\/\/www.infoq.cn\/article\/PfHdeTgybyC47SpAB2fo","title":"","type":null},"content":[{"type":"text","text":"避免不完全的雲原生（一）：雲原生到底意味着什麼？"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https:\/\/www.infoq.cn\/article\/LIRjAI0mhsClCooPtzLw","title":"","type":null},"content":[{"type":"text","text":"避免不完全的雲原生"}]}]}]}