調(diào)用lambda

by Yan Cui

崔燕

如何使用Lambda調(diào)用上下文動(dòng)態(tài)設(shè)置超時(shí) (How to set timeouts dynamically using Lambda invocation context)

With API Gate-way and Lamb-da, you’re forced to use short time-outs on the serv-er-side:

使用API?? Gateway和Lambda，您不得不在服務(wù)器端使用較短的超時(shí)：

• API Gate-way has a 29s max time-out on all inte-gra-tion points

  API網(wǎng)關(guān)在所有集成點(diǎn)上的最大超時(shí)為29秒

• The Server-less frame-work uses a default of 6s for AWS Lamb-da func-tions

  無(wú)服務(wù)器框架對(duì)AWS Lambda函數(shù)使用默認(rèn)值6s

How-ev-er, you have lim-it-ed influ-ence over a Lamb-da function’s cold start time. And you have no con-trol over how much over-head API Gate-way adds. So the actu-al laten-cy you’d expe-ri-ence from a call-ing func-tion is far less pre-dictable than you might think.

但是，你要通過(guò)lambda函數(shù)的冷啟動(dòng)時(shí)間的影響有限。 而且，您無(wú)法控制API網(wǎng)關(guān)添加多少開(kāi)銷。 因此，您從調(diào)用函數(shù)遇到的實(shí)際延遲遠(yuǎn)比您想象的要難預(yù)測(cè)。

We don’t want a slow HTTP respons-e to cause the call-ing func-tion to time-out. This has a negative impact on the user experience. Instead, we should stop wait-ing for a response before the call-ing func-tion times out.

我們不希望緩慢的HTTP響應(yīng)導(dǎo)致調(diào)用函數(shù)超時(shí)。 這對(duì)用戶體驗(yàn)有負(fù)面影響。 相反，我們應(yīng)該在調(diào)用函數(shù)超時(shí)之前停止等待響應(yīng)。

“The goal of the time-out strat-e-gy is to give HTTP requests the best chance to suc-ceed, pro-vid-ed that doing so does not cause the call-ing func-tion itself to err.”

“超時(shí)策略的目標(biāo)是為HTTP請(qǐng)求提供成功的最佳機(jī)會(huì)，前提是這樣做不會(huì)導(dǎo)致調(diào)用函數(shù)本身出錯(cuò)。”

- Me- 我

Most of the time, I see folks use fixed time-out val-ues — but it’s often tricky to decide:

在大多數(shù)情況下，我看到人們使用固定的超時(shí)值-但要決定通常很棘手：

• Too short, and you won’t give the request the best chance to suc-ceed. For example, there’s 5s left in the invo-ca-tion, but the time-out is set to 3s.

  太短了，您將不會(huì)給請(qǐng)求獲得成功的最佳機(jī)會(huì)。 例如，調(diào)用中還剩下5s，但是超時(shí)設(shè)置為3s。

• Too long, and you run the risk of let-ting the request time-out the call-ing func-tion. For example, there’s 5s left in the invo-ca-tion but the time-out is set to 6s.
  太長(zhǎng)了，您冒著使請(qǐng)求超時(shí)的調(diào)用函數(shù)的風(fēng)險(xiǎn)。 例如，調(diào)用中還剩下5s，但是超時(shí)設(shè)置為6s。

Things are fur-ther com-pli-cat-ed by the fact that we often per-form more than one HTTP request dur-ing a func-tion invo-ca-tion. For example,

在函數(shù)調(diào)用期間我們經(jīng)常執(zhí)行多個(gè)HTTP請(qǐng)求這一事實(shí)使事情變得更加復(fù)雜。 例如，

read from DynamoDB

從DynamoDB讀取

perform business logic on the data

對(duì)數(shù)據(jù)執(zhí)行業(yè)務(wù)邏輯

save the update to DynamoDB

將更新保存到DynamoDB

publish an event to Kinesis

向Kinesis發(fā)布事件

Let’s look at two com-mon approach-es for pick-ing time-out val-ues, and where they fall short.

讓我們看一下兩種選擇超時(shí)值的常見(jiàn)方法，以及它們的不足之處。

Instead of following these approaches, I propose we should set the request time-out based on the amount of invo-ca-tion time left. We should also reserve some time to per-form recovery steps in the event of failures.

我建議不要基于這些方法， 而應(yīng)根據(jù)剩余的調(diào)用時(shí)間來(lái)設(shè)置請(qǐng)求超時(shí) 。 如果發(fā)生故障，我們還應(yīng)該保留一些時(shí)間來(lái)執(zhí)行恢復(fù)步驟 。

You can find out how much time is left in the cur-rent invo-ca-tion through the context object.

您可以通過(guò)context對(duì)象找出當(dāng)前調(diào)用中還剩下多少時(shí)間。

For exam-ple, if a function’s timeout is 6s, and we’re 1s into the invocation. If we reserve 500ms for recov-ery, then that leaves us with 4.5s to wait for a HTTP response.

例如，如果一個(gè)函數(shù)的timeout為6s，而調(diào)用的timeout為1s。 如果我們保留500毫秒用于恢復(fù)，那么剩下4.5秒鐘的時(shí)間來(lái)等待HTTP響應(yīng)。

With this approach, we get the best of both worlds:

通過(guò)這種方法，我們可以兩全其美：

• Allow requests the best chance to suc-ceed based on the actu-al amount of invo-ca-tion time we have left
  允許請(qǐng)求根據(jù)我們剩下的實(shí)際調(diào)用時(shí)間獲得成功的最佳機(jī)會(huì)

• Pre-vent slow respons-es from tim-ing out the func-tion, which gives us a window of oppor-tu-ni-ty to per-form recov-ery actions.
  防止響應(yīng)緩慢導(dǎo)致功能超時(shí)，這為我們提供了執(zhí)行恢復(fù)操作的機(jī)會(huì)。

But what are you going to do after you time out these requests? Aren’t you still going to have to respond with a HTTP error, since you couldn’t fin-ish what-ev-er oper-a-tions you need-ed to per-form?

但是，這些請(qǐng)求超時(shí)后您將要做什么？ 由于您無(wú)法完成所需執(zhí)行的任何操作，您是否仍將不得不以HTTP錯(cuò)誤進(jìn)行響應(yīng)？

At the min-i-mum, the recov-ery actions should include:

至少，恢復(fù)操作應(yīng)包括：

• Log the timeout incident with as much context as possible. For example, request target, timeout value, correlation IDs, and the request object.

  使用盡可能多的上下文記錄超時(shí)事件。 例如，請(qǐng)求目標(biāo)，超時(shí)值， 相關(guān)性ID和請(qǐng)求對(duì)象。

• Track cus-tom met-rics for serviceX.timedout so it can be mon-i-tored and the team can be alert-ed if the sit-u-a-tion esca-lates

  跟蹤serviceX.timedout自定義指標(biāo)，以便在情況升級(jí)時(shí)可以對(duì)其進(jìn)行監(jiān)視并向團(tuán)隊(duì)發(fā)出警報(bào)

• Return an appli-ca-tion error code and the original request ID in the response body. The client app can then dis-play a user-friend-ly mes-sage like “Oops, looks like this fea-ture is cur-rent-ly unavail-able, please try again lat-er. If this is urgent, please con-tact us at xxx@domain.com and quote the request ID f19a7dca. Thank you for your coop-er-a-tion :-)”

  在響應(yīng)正文中返回應(yīng)用程序錯(cuò)誤代碼和原始請(qǐng)求ID。 然后，客戶端應(yīng)用程序可以顯示一條用戶友好的消息，例如“Oops, looks like this feature is currently unavailable, please try again later. If this is urgent, please contact us at xxx@domain.com and quote the request ID f19a7dca. Thank you for your cooperation :-)” “Oops, looks like this feature is currently unavailable, please try again later. If this is urgent, please contact us at xxx@domain.com and quote the request ID f19a7dca. Thank you for your cooperation :-)”

{ "errorCode": 10021, "requestId": "f19a7dca", "message": "service X timed out" }

In some cas-es, you can also recov-er even more grace-ful-ly using fall-backs.

在某些 情況下，您還可以使用后備功能更優(yōu)雅地恢復(fù)。

Netflix’s Hys-trix library sup-ports sev-er-al flavors of fall-backs via the Com-mand pat-tern it employs heav-i-ly. I recommend reading its wiki page, as there is tons of use-ful infor-ma-tion and ideas there.

Netflix的猬庫(kù)支持通過(guò)它使用大量的Command模式回退的幾種口味。 我建議閱讀其Wiki頁(yè)面 ，因?yàn)槟抢镉写罅坑杏玫男畔⒑拖敕ā?

Every Hystrix com-mand lets you spec-i-fy a fall-back action.

每個(gè)Hystrix命令都可以讓您指定一個(gè)后備操作。

You can also chain the fall-back togeth-er by chain-ing com-mands via their respec-tive getFallback meth-ods.

您還可以通過(guò)各自的getFallback方法將命令鏈接在一起，從而將后備鏈接鏈接在一起。

For exam-ple,

例如，

exe-cute a DynamoDB read inside CommandA

執(zhí)行CommandA內(nèi)部讀取的DynamoDB

In the getFallback method, exe-cute CommandB which would return a pre-vi-ous-ly cached response if avail-able

在getFallback方法中，執(zhí)行CommandB ，它將返回以前緩存的響應(yīng)(如果有)

If there is no cached response, then CommandB would fail and trig-ger its own getFallback method

如果沒(méi)有緩存的響應(yīng)，則CommandB將失敗并觸發(fā)自己的getFallback方法

Exe-cute CommandC, which returns a stubbed response

執(zhí)行CommandC ，它返回存根響應(yīng)

You should check out Hys-trix if you haven’t already. Most of the pat-terns that are baked into Hys-trix can be eas-i-ly adopt-ed in our server-less appli-ca-tions to help make them more resilient to fail-ures.

如果還沒(méi)有，請(qǐng)檢查Hystrix 。 大多數(shù)被烤成豪豬的模式可以在我們的無(wú)服務(wù)器應(yīng)用程序，幫助輕易采取使他們更適應(yīng)故障。

翻譯自: https://www.freecodecamp.org/news/how-to-set-timeouts-dynamically-using-lambda-invocation-context-3e78fa832a5b/

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