致敬《重構》：客戶端重構場景分析

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"《重構：改善既有代碼的設計》是計算機領域的一本經典之作，本書清晰揭示了重構的過程，解釋了重構的原理和最佳實踐方式，並給出了何時以及何地應該開始挖掘代碼以求改善。"}]},{"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":"距離該書首次出版已經過去了二十餘年，這二十多年裏行業發生了很多變化，但有一件事的必要性並沒有隨着技術的進步，工具的升級，方法論的擴展而被消滅："}]},{"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":"strong"}],"text":"這就是重構本身。"}]},{"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":"因爲在大部分工程師的職業經歷中，能夠從頭開始搭建一個項目，並且在時間充裕、需求明確的條件下，用正常節奏設計開發完整系統的過程只是一個美好的理想——更多時候是在接手的現有系統\/模塊中如何平衡好代碼質量和需求迭代。"}]},{"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":"本文的重點不是爲了說明重構的細節，而是從工程角度，在客戶端場景下給提出一些關於重構的建議；如果大家關心重構方法論本身，直接去閱讀《重構》就是最好的解答。"}]},{"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":"首先，爲什麼要強調客戶端？客戶端和其他場景有什麼區別？"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"我們簡單和後臺研發模式做個對比："}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"一般意義上的後端研發都是基於 SOA 思想的，通常一個子系統 3 個人一起維護，就已經是很充分的人力了，更多時候是 1 個主力 + 1 個 backup 的人力配置；"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"而客戶端則不同，一個公司戰略級的 app，多則一個端 50+人，少則十來個人也是正常配備。"}]}]}]},{"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":"但客戶端有個特徵："}]},{"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":"除非做了非常完善容器化，否則大家就得一起開發一些東西。"}]}]},{"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":"而即使做了容器化，很多狀態的共享是不可迴避的，比如："}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"A 模塊的 zombie，就足夠造成 B\/C\/D 任何一個模塊的 crash；"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"A 模塊的線程設計不合理很容易把接收回調的 B 模塊變得不可靠。"}]}]}]},{"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":"這一點和基於 SOA 思路設計的後臺服務中，一般故障都侷限在某個服務內部的特點有非常大的不同, 所以："}]},{"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":"strong"}],"text":"客戶端一個模塊被寫爛了，相比一個基於 MQ\/RPC 相互連接的後臺模塊或子系統，會對整個項目造成更大危害。"}]},{"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":"（這裏只是就代碼形式而言——不是說後臺就簡單了，後端複雜的場景往往在別的方面，會有類似架構設計是否支持平行擴展，故障如何隔離，服務怎麼降級等其他問題）"}]},{"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":"那麼什麼情況下必須立即重構，什麼情況下可以推遲重構？"}]},{"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":"其實沒有標準答案，但這就是造成問題的原因。"}]}]},{"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":"很多時候，研發會因爲各種原因，推遲重構，直到這件事情被一拖再拖，從重要而不緊急的事情變成了既重要也緊急的事情。"}]},{"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":"下面我會從之前的一些項目經驗中給出一些建議，供大家參考。"}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"重構的建議"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"要提前計劃重構，不要趕時間"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"大部分重構都是代碼債務的清償的過程，趕時間容易積累新的債務。"}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"緊急情況下做短期方案，但是必須比現在的狀況更優"}]}]}]},{"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":"比如：費了很大勁纔讀懂了一個長函數，如果本期沒時間優化，至少可以分解下這個大方法，寫出更多命名準確的子方法，在函數體內部調用，提升可讀性。"}]}]},{"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":"而對於一個突發的重構需求，其實已經錯過了解決問題的最佳時機。"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"小步穩跑，儘可能保證肉眼可見的正確性"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"大多數時候，我們很難找到整塊時間重構，這往往意味着你可能會相對分散地修改到正常需求開發不會觸碰的邏輯，這種情形對於 QA 同學來說是非常容易發生誤判的——即使和對方同步過，但雙方仍然可能對問題的影響面判斷不一致。"}]},{"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":"如果某些修改導致了用戶可感知的 bug，那麼這個時候往往容易因爲面臨各方壓力，而停止重構過程。"}]}]},{"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":"什麼叫 "},{"type":"text","marks":[{"type":"strong"}],"text":"肉眼可見的正確性？"},{"type":"text","text":" 概念很簡單，就是一些相對可靠的推論而已，比如：我改了一個變量類型，只要我足夠認真，同時確認過編譯器所有警告——那麼一個有經驗的程序員是可以保證這個修改風險可控的。"}]},{"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":"不同程度的工程師，能看出不同深度的問題，這一點需要執行重構的人，對自己的段位有客觀的評價，不要貪圖效率。"}]},{"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":"如果我沒有完全的把握確保這裏的線程使用是正確的，此時應該通過認真自測 + 和 QA 同學詳細同步影響面來確保安全，並且最好將自己懷疑會出問題的情形和對方指明。"}]}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"多做系統性方案，考慮越周到越好"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"之所以會重構，有很大一部分原因是因爲補丁方案已經快要 hold 不住了，這個時候再次使用小規模，單點方案，大概率會退化成另一種補丁。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"時間緊的情況下，想 100%，每次落地 x%, 保持方向正確，一步到位不了，兩步，三步……"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"堅持做，代碼會累積的你的努力。"}]},{"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":"在複雜度面前，任何可以累積的努力，都最終會變得有效。"}]}]},{"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":"不過，是否這個假設過於樂觀了，有累積不了的情況嗎？有的，看下面。"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"單兵收斂重點"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"有些複雜的事情必須要有單點管控，人越多越亂："}]},{"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":"因爲很多重構必須要有全局觀，才能抽象出比較符合項目實際情況的方案。"}]}]},{"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":"如果發現單兵速度跟不上團隊其他人驅動的工程演進速度，這一點需要認真想辦法解決，否則就是浪費資源，原因例如："}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"單兵修改和團隊修改有重疊：人力有限的時候做組件化開荒很容易遇到這種情況；"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"單兵無法控制在較短時間內完成修改，完成之後和 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bug 量。"}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"總結"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最後分享一個博弈論問題："}]},{"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":"如果兩個敵對國家的特工理解情報的能力不一樣，且需要根據情報互相博弈——A 可以 100%理解，B 只能理解 10%，那麼在獲取相同信息的前提下，什麼情況下 B 可以獲得高於 10%勝率？"}]}]},{"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":"答案很有意思：大量增加情報數量和複雜度，直到遠遠超出 A 的個人能力，這個時候 B 就有可能獲得 50%的勝算。"}]},{"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":"這個可能也是爲什麼很多非常優秀的團隊仍然會陷在 bug 泥潭裏的原因，系統的熵太大。"}]},{"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":"正如熱力學中所說的熵增一樣，宇宙萬物永遠都在經歷着從有序到混亂的過程，代碼也不例外，但"}]},{"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":"生命不同，它是反熵的。"}]}]},{"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":"優秀工程師始終會通過各種手段來控制複雜度，從而賦予代碼某種生命的特徵，也許能從側面印證一個說法——"},{"type":"text","marks":[{"type":"strong"}],"text":"好的代碼是活的"},{"type":"text","text":"。"}]},{"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":"本文轉載自：字節跳動技術團隊（ID：toutiaotechblog）"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"原文鏈接："},{"type":"link","attrs":{"href":"https:\/\/mp.weixin.qq.com\/s\/pUjRhORgMNK45GBTt9RtLg","title":"xxx","type":null},"content":[{"type":"text","text":"致敬《重構》：客戶端重構場景分析"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}}]}