Caching 当S3源视频/mp4资源替换为更大的文件时，来自cloudfront的416

为什么在下面的场景中cloudfront会以416状态响应，尽管我认为请求的范围应该是可以满足的

原始S3对象 情景：

使用S3源配置cloudfront分发，对象缓存设置为“自定义”，最小/最大/默认TTL全部设置为0

将视频/mp4文件上载到S3，不设置与缓存相关的头

通过cloudfront在chrome中播放视频

在这一点上，一切似乎都很好。我看到3个网络请求资源-为什么chrome请求2和3的重叠范围，我不明白，但尽管如此，视频在这一点上播放得很好

覆盖S3对象 现在，不久之后：

将较大的（~2x）文件上载到相同的S3位置

通过cloudfront在chrome中播放视频

这一次，发生了一个错误

这里的resp 1似乎是正常的（即内容长度看起来是正确的）-虽然不确定为什么它是来自cloudfront的

未命中

-鉴于TTL设置，我本以为它是

刷新命中

为什么即使请求的范围在resp 1的内容长度范围内，第二页加载的“req 2”也会因416而失败？

注:

• 直接转到S3，没有问题
• 将较大的文件替换回较小的文件，视频将再次正常播放
• 使用“缓存控制：无缓存”将文件上载到S3，没有问题，但我总是收到“来自cloudfront的未命中”。我的理解是，cloudfront应该始终使用S3检查内容是否随此配置而改变
• 等待一段时间（比如30秒）-问题自行解决
• 以前尝试复制此场景时，在覆盖之后，S3向CloudFront添加了304个响应，但我无法复制该行为（现在只有一个216个）

---

日志 原始S3对象 铬 云锋 S3 云锋 S3

8CD9B72DE42431DF4ADADADAB73AABF29EA0B34B5D821565FE4A16A3080509坏视频测试[11/Dec/2016:23:24:06+0000]150.101.108.33 arn:aws:iam:：：user/E58826B8A66DBA1B REST.PUT.OBJECT video.mp4“PUT/video.mp4 HTTP/1.1“200--956852 7367 53”-“aws cli/1.9.11/2.7.10 Darwin/16.1.1.0 botocore/1.4.26”-
8CD9B72DE42431DF4DADAB73AABF29EA0B34B5D821565FE4A16A3080509坏视频测试[11/Dec/2016:23:24:18+0000]54.239.202.45-BA1C06FEA7DAC83F REST.GET.OBJECT video.mp4“GET/video.mp4 HTTP/1.1”206-956852 956852 40 35-“亚马逊云前端”-

您看不到的是，在覆盖后的第一个请求中，S3向CloudFront提供的是哪个对象——旧对象还是新对象

当您在S3中覆盖现有对象时，覆盖始终是一个原子操作，从这个意义上说，每个请求都将通过完整的旧对象或完整的新对象来满足。。。但是时间并不能保证，因为S3有一个覆盖现有对象的最终一致性模型

AmazonS3为所有区域的覆盖放置和删除提供了最终的一致性

对单个密钥的更新是原子的。例如，如果您对现有密钥执行PUT操作，后续读取可能会返回旧数据或更新的数据，但它永远不会写入损坏或部分数据

即使bucket没有启用版本控制，当两个对象都存在于S3中时，也会有一个时间窗口（通常很短）。考虑到上述陈述是正确的，这不可能是任何其他方式

类似地，也可以从S3请求一个不存在的对象，然后上传该对象，然后再次请求它，并在下载成功之前继续获得404（或403，取决于bucket配置）响应一小段时间

相反，如果从未尝试下载不存在的对象，则在上载后，您将始终发现该对象可立即下载。这是一种折衷，本质上是大规模设计的必要性

bucket和distribution日志应该有助于揭示幕后发生的事情，特别是在上传后的任何下载尝试中从S3进行CloudFront下载时，如果显示与旧对象一致的字节计数

---

经过进一步思考这里还有第二种可能的解释这里发生了什么，很难决定这是否被认为是CloudFront中的错误，如果这确实是实际问题的话

在S3中替换对象之后，让我们暂时假设一致性不是问题——让我们假设上传之后的所有后续请求实际上都会导致S3向CloudFront提供对象的当前版本

这里的问题可能是，在对象被替换后的第一次下载——这本应导致CloudFront收回其对象的旧缓存版本——被浏览器取消。（我见过Chrome这样做，但我不知道它为什么这样做。）

取消下载时，源站的响应不会被缓存

取消的请求

如果某个对象不在边缘缓存中，并且如果在CloudFront从您的源站获取该对象后但在它可以交付请求的对象之前，查看器终止了会话（例如，关闭浏览器），则CloudFront不会将该对象缓存在边缘位置

当然，这表示“如果对象不在边缘缓存中”，您可以争辩说它实际上是。。。但这可能是一个语义问题：CloudFront从S3请求的对象可能不在缓存中——缓存中的对象是不同的对象（在相同的URI）。如果这个逻辑成立，那么“CloudFront不缓存对象”的断言也可能成立

所以。。。

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2016-12-11      23:24:19        MEL50   52198   150.101.108.33  GET     dvayusv1lektq.cloudfront.net    /video.mp4      206     -       Mozilla/5.0%2520(Macintosh;%2520Intel%2520Mac%2520OS%2520X%252010_12_1)%2520AppleWebKit/537.36%2520(KHTML,%2520like%2520Gecko)%2520Chrome/55.0.2883.87%2520Safari/537.36        u=1481498656967 -       Error   CjmlHAFcyEWCiV68Q0G3gltuQSV7maR5bUoX0CfngDgDBp5fDvI38A==        dvayusv1lektq.cloudfront.net    https   46      1.551   -       TLSv1.2 ECDHE-RSA-AES128-GCM-SHA256     Miss    HTTP/2.0
2016-12-11      23:24:19        MEL50   302     150.101.108.33  GET     dvayusv1lektq.cloudfront.net    /video.mp4      416     -       Mozilla/5.0%2520(Macintosh;%2520Intel%2520Mac%2520OS%2520X%252010_12_1)%2520AppleWebKit/537.36%2520(KHTML,%2520like%2520Gecko)%2520Chrome/55.0.2883.87%2520Safari/537.36        u=1481498656967 -       Error   WIb50z_8rXTdqaC4CzUSYSL0kuIE9CWlCnKNgzps7AoCSRoJplBBbA==        dvayusv1lektq.cloudfront.net    https   47      0.001   -       TLSv1.2 ECDHE-RSA-AES128-GCM-SHA256     Error   HTTP/2.0

8cd9b72de42431df1df4dadadab73aabf29ea0b34b5d821565fe4a16a3080509 bad-video-test [11/Dec/2016:23:24:06 +0000] 150.101.108.33 arn:aws:iam::<IAM ID>:user/<username> E58826B8A66DBA1B REST.PUT.OBJECT video.mp4 "PUT /video.mp4 HTTP/1.1" 200 - - 956852 7367 53 "-" "aws-cli/1.9.11 Python/2.7.10 Darwin/16.1.0 botocore/1.4.26" -
8cd9b72de42431df1df4dadadab73aabf29ea0b34b5d821565fe4a16a3080509 bad-video-test [11/Dec/2016:23:24:18 +0000] 54.239.202.45 - BA1C06FEA7DAC83F REST.GET.OBJECT video.mp4 "GET /video.mp4 HTTP/1.1" 206 - 956852 956852 40 35 "-" "Amazon CloudFront" -