s3

Hi. First of all, kudos to you for the VFS cache - it's really brilliant. I have one request though.

For a little background, as of now I'm using the following settings:

--vfs-cache-mode full \
  --vfs-cache-max-size 500G \
  --vfs-cache-max-age 5000h \
  --vfs-cache-poll-interval 5m \
  --vfs-read-ahead 2G \
  --bwlimit-file 32M \
  --vfs-read-chunk-size=64M \
  --vfs-read-chunk-s

These are all functions/structs for configuring the same thing:

https://github.com/thanos-io/thanos/blob/5bda2d48b9ef0bf138af6132641eb20102223edb/pkg/objstore/azure/helpers.go#L121
https://github.com/thanos-io/thanos/blob/46ac4d590e783368fc4ec7676f29ff97cd0bd630/pkg/objstore/cos/cos.go#L95
https://github.com/thanos-io/thanos/blob/bf963237e0b95402aeea4093dce465abde055675/pkg/objstore/s3/s3.go#

What went wrong?

I'm getting deprecation warnings with openSSL encryption.

[2019/09/05 08:38:52][info] Using Encryptor::OpenSSL to encrypt the archive.
[2019/09/05 08:40:22][warn] Pipeline STDERR Messages:
[2019/09/05 08:40:22][warn] (Note: may be interleaved if multiple commands returned error messages)
[2019/09/05 08:40:22][warn]
[2019/09/05 08:40:22][warn] *** WARNING : depre

Problem description

Hi, smart_open currently supports hdfs://, viewfs:// is also a hadoop file system which is similar to hdfs://.

I find that tf.io.gfile.GFile of tensorflow can support both hdfs:// and viewfs://, is it possible that smart_open add support for viewfs://?

Thanks~