盘点Serverless架构的六个特质

{"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":"编译 | 刘雅梦"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"策划 | 辛晓亮"}]},{"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":"本文介绍了Serverless（无服务器）架构的六个特质（Traits）：入门门槛低（Low barrier-to-entry）、无主机（Hostless）、无状态（Stateless）、弹性（Elasticity）、分布式（Distributed）和事件驱动（Event-driven）。其目的是倡导大家尽可能广泛地采用Serverless架构。Serverless架构带来了一个有趣的范式转变，这使得软件开发的许多方面都变得更好了。但它也带来了技术人员必须要适应的新挑战。对于如何应对每种特质所带来的挑战，我也给出一些简短的建议，希望这些挑战不会阻止大家采用Serverless架构。"}]},{"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":"每当新技术出现时，技术专家的首要任务就是要理解采用新技术的意义。Serverless（无服务器）架构就是一个很好的例子。"}]},{"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，目前关于Serverless架构的文献大多都只关注于它的优点。许多文章（以及使用示例）都是由云供应商推出的，因此，会毫不意外地谈论其积极方面。本文的意图是让大家更好地理解Serverless架构的特质。"}]},{"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":"我特意选了特质（Trait）这个词，而不是特性（Characteristic），因为这些是Serverless架构的元素，我们无法更改它们。Characteristic特性是可塑的，而Trait特质是固有的。Trait特质也是中性的，因此它既不是积极的也不是消极的。在某些情况下，我所描述的某些类型的Trait特质可能具有积极的含义，但我会保持中立的态度，以便你了解自己将要面对的是什么。"}]},{"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特质也是内在的，因此你必须要接受它们，而不是与之抗争，因为这样尝试的话可能会付出相当大的代价。另一方面， Characteristic特性需要花费精力去塑造它们，然而你还是可能会把它们搞错。"}]},{"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":"我还应该向大家介绍Mike Roberts的这篇文章，他也探讨了"},{"type":"link","attrs":{"href":"https:\/\/blog.symphonia.io\/defining-serverless-part-1-704d72bc8a32","title":null,"type":null},"content":[{"type":"text","text":"Serverless服务"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"的Traits特质。尽管我们在这里使用了相同的术语，但值得注意的是，本文所研究的是架构的Traits特质，而不是你所使用的服务的Traits特质。"}]},{"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":"本文的目的不是帮助你深入理解所有的主题，而是为你提供一个大致的概述。以下是本文中定义的Serverless架构的Traits特质："}]},{"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":"入门门槛低（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":"无主机（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":"无状态（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":"弹性（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":"分布式（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":"事件驱动（Event-driven）"}]}]}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"入门门槛低"}]},{"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":"让你的代码开始在Serverless架构中运行相对来说是简单的。你可以参照任何教程来开始，并让代码在生产级生态系统中运行。在许多方面，Serverless架构的学习曲线并没有典型的"},{"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":"那么令人生畏——当你使用Serverless架构时，DevOps的许多元素就都是不必要的了。例如，你不必学习服务器管理技能，如配置管理或补丁。这就是为什么入门门槛低是Serverless架构的Traits特质之一。"}]},{"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":"这意味着，最初开发人员的学习曲线比许多其他架构风格的曲线都要低。但这并不意味着学习曲线会一直保持在较低的水平，事实上，随着开发人员继续他们的旅程，整体学习曲线将会变得更陡峭。"}]},{"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":"由于这种架构特质，我看到许多新的开发人员很快就加入到了项目中，并且他们能够有效地为项目做出贡献。开发人员能够快速上手，这可能是Serverless项目能"},{"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":"正如我们所指出的那样，事情确实会变得更加复杂。例如，基础设施即代码（Infrastructure as a code，Iac）、日志管理、监控，有时还包括网络，这些仍然都是必不可少的。你必须要了解如何在Serverless的世界中实现它们。如果你来自不同的开发背景，那么你需要了解一些Serverless架构的Traits特质（本文将介绍这些Traits特质）。"}]},{"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":"尽管最初的入门门槛很低，但开发人员不应该认为他们可以忽略重要的架构原则。"}]}]},{"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，一些开发人员倾向于认为Serverless架构意味着他们不必考虑代码设计。理由是他们只是在处理函数，所以代码设计是无关紧要的。事实上，像SOLID这样的设计原则仍然适用——你不能将代码的可维护性外包给你的Serverless平台。尽管你可以将代码打包并上传到云上运行，但我强烈建议你不要这样做，因为持续交付实践在Serverless架构中仍然是相关的。"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"无主机"}]},{"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架构的一个明显特质是，你无需直接处理服务器。在这个时代，你可以在各种各样的主机上安装并运行服务——无论是物理机、虚拟机、容器等等——用一个词来描述这一点是很有用的。为了避免使用已经使用过的术语“无服务器”（“serverless”），我将在这里使用“主机”（“host”，术语“主机”在"},{"type":"link","attrs":{"href":"https:\/\/www.thoughtworks.com\/books\/building-microservices","title":null,"type":null},"content":[{"type":"text","text":"《构建微服务》"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"一书中使用过）这个词，因此该Trait特质名为“无主机”（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":"无主机的一个优势是，你在服务器维护方面的操作开销将会大大减少。你无需再为升级服务器而忧心，安全补丁将自动为你执行。无主机还意味着在应用程序中你需要监控的度量指标也会不同。这是因为你使用的大多数底层服务不会再发布CPU、内存、磁盘大小等传统度量指标了。这意味着你不再需要理解架构的低级操作细节。"}]},{"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":"但不同的监控指标意味着，你必须重新学习如何调整你的架构。AWS DynamoDB提供了可以供你进行监控和调控的读写能力，这是一个你必须要了解的概念，而且这种学习是不能迁移到其他Serverless平台的。你使用的每项服务都有其局限性。AWS Lambda具有并发执行的限制，你所拥有的CPU核数不存在限制。更奇怪的是，更改Lambda的内存分配大小将会更改获得的CPU核数。如果你为了性能测试和生产环境共享一个AWS帐户，那么如果性能测试意外地消耗了你的全部并发执行限制，可能会导致生产的宕机。AWS很好地记录了每项服务的限制，因此请务必检查它们，以便做出正确的架构决策。"}]},{"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":"一个常见的误解是，Serverless应用程序更安全，因为安全补丁会自动应用于你的底层服务器。这个假设很危险。"}]}]},{"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":"由于Serverless架构具有不同的攻击向量，传统的安全防护已不再适用。应用程序的安全实践仍然适用，并且在代码中存储秘密仍然是一个很大的禁忌。AWS在其"},{"type":"link","attrs":{"href":"https:\/\/aws.amazon.com\/compliance\/shared-responsibility-model\/","title":null,"type":null},"content":[{"type":"text","text":"责任共担模式"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"中概述了这一点，例如，如果数据包含敏感信息，你仍然需要保护数据。我强烈建议你阅读"},{"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项目"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"以获得更多有关该主题的见解。"}]},{"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":"虽然你的运维操作开销大大减少了，但值得注意的是，在极少数情况下，你仍然需要管理底层服务器更改后的影响。你的应用程序可能依赖于原生库，并且你需要确保在升级基础操作系统时它们仍可以工作。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":"操作系统最近已升级到了"}],"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":"无状态"}]},{"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":"函数即服务，即FaaS，是很短暂的，因此你不能在内存中存储任何内容，因为运行代码的计算容器将由平台自动创建和销毁。因此，无状态（Stateless）是Serverless架构中的一个Trait特质。"}]},{"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":"无状态是水平扩展应用程序的一个很好的特质。无状态的概念是鼓励你在应用程序中不要存储状态。通过不在应用程序中存储状态，你将能够启动更多的实例，而无需担心应用程序的状态，从而实现水平扩展。我在这里发现了一个有趣的点，实际上无状态是被迫的，因此错误的空间大大减少了。是的，这里有一些注意事项：例如，计算容器可能会被重复使用，你可以存储状态，但是如果你采用这种方法，请务必谨慎处理。"}]},{"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":"就应用程序开发而言，你将无法使用需要状态的技术，因为状态管理的负担是强加给调用方的。例如，不能使用HTTP会话，因为你没有具有持久化文件存储的传统Web服务器。如果你想使用WebSockets等需要状态的技术，那么你需要等待，"},{"type":"link","attrs":{"href":"https:\/\/serverless.com\/blog\/api-gateway-websockets-support\/","title":null,"type":null},"content":[{"type":"text","text":"等到相应的后端即服务（BaaS）支持这些技术为止"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"，或者应用你自己的解决方案。"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"弹性"}]},{"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":"由于你的架构是无主机的，那么你的架构也将具有弹性的特质。 你使用的大多数Serverless服务都被设计为具有高弹性，你可以从零扩展到允许的最大值，然后再回到零，大部分是自动管理的。 弹性是Serverless架构的一个Trait特质。"}]},{"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":"对于可扩展性来说，弹性的好处是巨大的。这意味着你不必手动管理资源扩展。资源分配的许多挑战都消失了。在某些情况下，具有弹性可能只意味着你只需为所使用的内容付费，因此，如果你的使用模式较低，则可以降低运行成本。"}]},{"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":"你可能需要将Serverless架构与不支持这种弹性的遗留系统集成。当这种情况发生时，你可能会破坏下游系统，因为它们可能无法像Serverless架构那样扩展。如果你的下游系统是关键系统，那么考虑如何缓解此问题是至关重要的——可能是通过限制AWS Lambda的并发性或利用队列与下游系统对话。"}]},{"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":"虽然在这种高弹性的情况下，“拒绝服务”攻击（denial of service，DOS）将会变得更加困难，反而更容易受到“拒绝钱包”（denial of wallet）攻击。在这种情况下，攻击者试图通过强制增加资源分配来迫使你超出云帐户的限制，从而破坏应用程序。为了防止这种攻击，你可能会发现在你的应用程序中使用DDoS保护（如AWS Shield）是很有帮助的。在AWS中，设置AWS预算也很有用，这样当你的云账单暴涨时，你就会收到通知。如果高弹性不是你所期望的，那么在应用程序上设置约束是很有用的，比如通过限制AWS Lambda并发性。"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"分布式"}]},{"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":"由于无状态计算是一种特质，所有的持久性需求都将存储在后端即服务（BaaS）中，通常是BaaS的组合中。一旦你更多地使用FaaS，你还会发现你的部署单元（即函数）比你已习惯了的可能还要小。因此，在默认情况下，Serverless架构是分布式的，并且有许多组件必须要通过网络来进行集成。你的架构还将包括将服务连接在一起，比如身份验证、数据库、分布式队列等。"}]},{"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":"分布式系统有很多好处，比如我们前面讨论过的弹性。在默认情况下，分布式还能为你的架构带来了单区域的高可用性。在Serverless环境中，当云供应商所在区域的某个可用性区域出现故障时，你的架构将能够利用其他仍在运行的可用性区域——从开发人员的角度来看，所有这些都是不透明的。"}]},{"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":"在选择架构时总要权衡利弊。在这个特质中，你牺牲了一致性来换取可用性。通常在云上，每个Serverless服务也都有自己的一致性模型。例如，在AWS S3中，通过在S3桶中对新对象的PUT操作可以获得“写后读”（read-after-write）的一致性。对于对象更新，S3是最终一致的。对于你来说，决定使用哪种BaaS是很常见的，因此要注意它们的一致性模型的行为。"}]},{"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":"另一个挑战是你需要熟悉分布式消息的传递方法。例如，你需要熟悉并了解"},{"type":"link","attrs":{"href":"https:\/\/martinfowler.com\/bliki\/TwoHardThings.html","title":null,"type":null},"content":[{"type":"text","text":"精确一次投递（exactly-once delivery）"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"这一难题，因为分布式队列的常见消息投递方式是至少一次投递（at-least-once-delivery）。由于这种投递方式，AWS Lambda可以被多次调用，因此你必须确保你的实现是幂等的（了解FaaS的重试行为也很重要，其中AWS Lambda可能会在失败时多次执行）。你需要了解的其他挑战还包括分布式事务的行为。然而，随着微服务的普及，构建分布式系统的学习资源一直在演进。"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"事件驱动"}]},{"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平台提供的许多BaaS自然会支持事件。对于第三方服务来说，这是一个很好的策略，它们可以为其用户提供可扩展性，因为你无法控制他们服务的代码。由于你将在Serverless架构中使用大量的BaaS，因此你的架构是具有事件驱动这一Trait特质的。"}]},{"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":"我还认识到，即使你的架构是具有事件驱动这一Trait特质的，但这并不意味着你需要完全采用事件驱动的架构。然而，我观察到，当将事件驱动架构自然地提供给团队时，团队更倾向于接受它。这个特质和弹性特质类似，不需要时，你仍然可以关闭它。"}]},{"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":"事件驱动能带来很多好处。架构组件之间的耦合程度很低。在Serverless架构中，你可以很容易地引入一个新函数来监听blob存储中的更改："}]},{"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，当添加函数B时，函数A并没有改变（参见图1）。这增加了函数的内聚性。函数具有高内聚是有很多好处的，其中一个好处是当单个操作失败时，你可以轻松地重试该操作。当函数B失败重试时，意味着你不需要运行高昂的函数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":"特别是在云计算中，云供应商将确保你的FaaS与他们的BaaS能够轻松集成。FaaS可以被设计成由"},{"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":"触发。"}]},{"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":"事件驱动架构的缺点是，开始时你可能会失去系统作为一个整体的整体视图。这会使得对系统进行故障排除变得更具挑战性。分布式跟踪是你应该研究的一个领域，尽管它在Serverless架构中仍然是一个成熟的领域。AWS X-Ray是一种可以在AWS中开箱即用的服务。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":"确实有其自身的局限性"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"，如果你已经超越了它，你应该关注这个领域，因为有第三方的产品正在涌现。这就是为什么记录关联ID（Correlation IDs）的实践是必不可少的，特别是在事务中使用多个BaaS的情况下。所以一定要确保实现关联ID。"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"结论"}]},{"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":"本文介绍了Serverless架构的六个Traits特质：入门门槛低、无主机、无状态、弹性、分布式和事件驱动。我的目的是倡导大家尽可能广泛地采用Serverless架构。Serverless架构带来了一个有趣的范式转变，这使得软件开发的许多方面都变得更好了。但它也带来了技术人员必须要适应的新挑战。对于如何应对每种Trait特质所带来的挑战，我也给出一些简短的建议，希望这些挑战不会阻止你采用Serverless架构。"}]},{"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":"原文链接："}]},{"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"}}]}]}]}