This PR improves the replication failure healing by persisting
most recent failures to disk and re-queuing them until the replication
is successful.
While this does not eliminate the need for healing during a full scan,
queuing MRF vastly improves the ETA to keeping replicated buckets
in sync as it does not wait for the scanner visit to detect unreplicated
object versions.
competing calls on the same object on versioned bucket
mutating calls on the same object may unexpected have
higher delays.
This can be reproduced with a replicated bucket
overwriting the same object writes, deletes repeatedly.
For longer locks like scanner keep the 1sec interval
This PR fixes possible leaks that may emanate from not
listening on context cancelation or timeouts.
```
goroutine 60957610 [chan send, 16 minutes]:
github.com/minio/minio/cmd.(*erasureServerPools).Walk.func1.1.1(...)
github.com/minio/minio/cmd/erasure-server-pool.go:1724 +0x368
github.com/minio/minio/cmd.listPathRaw({0x4a9a740, 0xc0666dffc0},...
github.com/minio/minio/cmd/metacache-set.go:1022 +0xfc4
github.com/minio/minio/cmd.(*erasureServerPools).Walk.func1.1()
github.com/minio/minio/cmd/erasure-server-pool.go:1764 +0x528
created by github.com/minio/minio/cmd.(*erasureServerPools).Walk.func1
github.com/minio/minio/cmd/erasure-server-pool.go:1697 +0x1b7
```
The bottom line is delete markers are a nuisance,
most applications are not version aware and this
has simply complicated the version management.
AWS S3 gave an unnecessary complication overhead
for customers, they need to now manage these
markers by applying ILM settings and clean
them up on a regular basis.
To make matters worse all these delete markers
get replicated as well in a replicated setup,
requiring two ILM settings on each site.
This PR is an attempt to address this inferior
implementation by deviating MinIO towards an
idempotent delete marker implementation i.e
MinIO will never create any more than single
consecutive delete markers.
This significantly reduces operational overhead
by making versioning more useful for real data.
This is an S3 spec deviation for pragmatic reasons.
Queue failed/pending replication for healing during listing and GET/HEAD
API calls. This includes healing of existing objects that were never
replicated or those in the middle of a resync operation.
This PR also fixes a bug in ListObjectVersions where lifecycle filtering
should be done.
