PUT shall only proceed if pre-conditions are met, the new
code uses
- x-minio-source-mtime
- x-minio-source-etag
to verify if the object indeed needs to be replicated
or not, allowing us to avoid StatObject() call.
Do completely independent multipart uploads.
In distributed mode, a lock was held to merge each multipart
upload as it was added. This lock was highly contested and
retries are expensive (timewise) in distributed mode.
Instead, each part adds its metadata information uniquely.
This eliminates the per object lock required for each to merge.
The metadata is read back and merged by "CompleteMultipartUpload"
without locks when constructing final object.
Co-authored-by: Harshavardhana <harsha@minio.io>
