Use decodeUtf8' to check whether bytestrings are printable before logging

[korayal]

closes #947

on my local tests targeting localstack, below are the results when I hit the PutMetricData endpoint via a gzipped wrapper

[Client Request] {
  host      = localhost:4566
  secure    = False
  method    = POST
  target    = Nothing
  timeout   = ResponseTimeoutMicro 300000000
  redirects = 0
  path      = /
  query     =
  headers   = x-amz-content-sha256: e769f604d04a6c9f5f05218ea59e10ae8e728e64cff3dc4a2ca47b0b41c453e8; x-amz-date: 20230731T124639Z; host: localhost:4566; content-encoding: gzip; content-type: application/x-www-form-urlencoded; charset=utf-8; authorization: AWS4-HMAC-SHA256 Credential=localstack_key_id/20230731/us-east-1/monitoring/aws4_request, SignedHeaders=content-encoding;content-type;host;x-amz-content-sha256;x-amz-date, Signature=22efa655b91759f5deba281860a38ae9560065cfc2f16be198e51a4a95b93098
  body      = non-printable 365 strict bytes
}

or, when the data is printable (no gzipped payload):

[Client Request] {
  host      = localhost:4566
  secure    = False
  method    = POST
  target    = Nothing
  timeout   = ResponseTimeoutMicro 300000000
  redirects = 0
  path      = /
  query     =
  headers   = x-amz-content-sha256: efbf2bd7e9a1e0cdf2ee1b29225678f489d9d1d9baed20dde625d0faf56472fd; x-amz-date: 20230731T125748Z; host: localhost:4566; content-type: application/x-www-form-urlencoded; charset=utf-8; authorization: AWS4-HMAC-SHA256 Credential=localstack_key_id/20230731/us-east-1/monitoring/aws4_request, SignedHeaders=content-type;host;x-amz-content-sha256;x-amz-date, Signature=47dfedcd0d705427f27f78b8640026ee254a622bf6e973eb01d973af2b2caf81
  body      = Action=GetMetricStatistics&Dimensions.member.1.Name=test_id&Dimensions.member.1.Value=test10&EndTime=2023-07-31T12%3A57%3A48Z&MetricName=instrument-test&Namespace=test-namespace&Period=60&StartTime=2023-07-31T12%3A57%3A46Z&Statistics.member.1=SampleCount&Version=2010-08-01
}

[endgame]

Can you please add an entry to lib/amazonka/CHANGELOG.md, which is the master changelog for the project?

Also, are we sure that this is the correct check to make? What if the user's terminal is set to some other encoding scheme? A TextEncoding (as returned by System.IO.hGetEncoding) isn't even in Eq, so I'm not sure what the best way is to fix this. I suspect what we have here might be a bit too naive; do you have any thoughts about other ways we could check this? It may also be the case that we successfully decode UTF-8 but it's got non-printable characters in it; do we want to do that check here too?

In the medium term, I probably want to extract logging from the main amazonka library so that people can use whatever logging framework suits them. Then handling non-printable stuff becomes the log library's concern.

[korayal]

Can you please add an entry to lib/amazonka/CHANGELOG.md, which is the master changelog for the project?

I've updated the changelog and added a section Unreleased at the top. would that work?

[korayal]

Also, are we sure that this is the correct check to make? What if the user's terminal is set to some other encoding scheme? A TextEncoding (as returned by System.IO.hGetEncoding) isn't even in Eq, so I'm not sure what the best way is to fix this. I suspect what we have here might be a bit too naive; do you have any thoughts about other ways we could check this? It may also be the case that we successfully decode UTF-8 but it's got non-printable characters in it; do we want to do that check here too?

I've added another check with isPrint, where it should ensure that whatever we're trying to print contains printable characters. At this point I think assuming "the request body (if not compressed) is a valid utf-8 text" should be fine since it's what we're sending to AWS. The part that prints it out is still left to Build.lazyByteString / Build.byteString, so at worst case we're keeping the existing behavior.

In the medium term, I probably want to extract logging from the main amazonka library so that people can use whatever logging framework suits them. Then handling non-printable stuff becomes the log library's concern.

that'd be great.

[korayal]

@endgame are we OK with the latest state of this PR?

[endgame]

Thank you for this, and sorry for the delay.