seeing lots of 4xx errors in s3 bucket metrics, but not on the client side

Question

we are seeing lots of 4xx errors in the s3 bucket metrics
![4xx errors](/media/postImages/original/IMCTpGgCOKTeyNvCq-hweTWQ)
the error count is roughly aligned with the put traffic 
![put traffic](/media/postImages/original/IMIEofmsCFReiY898KIttA1w)

but on **the client side**, we don't see any error on our side. 
is the 4xx error internal? how do i interpret the numbers?

Thanks!

Answer

May I suggest that you temporarily enable [S3 server access logging](https://docs.aws.amazon.com/AmazonS3/latest/userguide/enable-server-access-logging.html), so as to identify the root cause through fields `HTTP status` and `Error Code`?

---

For instance, the following entry indicated a `HTTP status` **404** with `Error Code` **NoSuchBucketPolicy**. Visit [this documentation](https://docs.aws.amazon.com/AmazonS3/latest/userguide/LogFormat.html) for more information.

```
79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be DOC-EXAMPLE-BUCKET1 [06/Feb/2019:00:00:38 +0000] 192.0.2.3 79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be A1206F460EXAMPLE REST.GET.BUCKETPOLICY - "GET /DOC-EXAMPLE-BUCKET1?policy HTTP/1.1" 404 NoSuchBucketPolicy 297 - 38 - "-" "S3Console/0.4" - BNaBsXZQQDbssi6xMBdBU2sLt+Yf5kZDmeBUP35sFoKa3sLLeMC78iwEIWxs99CRUrbS4n11234= SigV4 ECDHE-RSA-AES128-GCM-SHA256 AuthHeader DOC-EXAMPLE-BUCKET1.s3.us-west-1.amazonaws.com TLSV1.2 - Yes 
```

seeing lots of 4xx errors in s3 bucket metrics, but not on the client side

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