improvements in this PR include
- decommission objects that have __XLDIR__ suffix
- decommission objects that have `null` version on
a versioned bucket.
- make sure to look for any "decom" failures to ensure
that we do not wrong conclude decom as complete without
all files getting copied over.
- break out eagerly upon first error for objects with
multiple versions, leave the object as is for support
debugging and analysis.
without this wait there is a potential for some objects
that are in actively being decommissioned would cancel,
however the decommission status might wrongly conclude
this as "Complete".
To avoid this make sure to add waitgroups on the parallel
workers, allowing parallel copies to complete fully before
we return.
currently an on-going decommission, during a server
restart might block the startup sequence for relatively
longer periods, instead start the decommission in
background lazily.
some upgraded objects might not get listed due
to different quorum ratios across objects.
make sure to list all objects that satisfy the
maximum possible quorum.
do not allow mutation to pool command line when there are
unfinished decommissions in place, disallow such scenarios
to avoid user mistakes.
also add testcases to cover all relevant scenarios.
```
λ mc admin decommission start alias/ http://minio{1...2}/data{1...4}
```
```
λ mc admin decommission status alias/
┌─────┬─────────────────────────────────┬──────────────────────────────────┬────────┐
│ ID │ Pools │ Capacity │ Status │
│ 1st │ http://minio{1...2}/data{1...4} │ 439 GiB (used) / 561 GiB (total) │ Active │
│ 2nd │ http://minio{3...4}/data{1...4} │ 329 GiB (used) / 421 GiB (total) │ Active │
└─────┴─────────────────────────────────┴──────────────────────────────────┴────────┘
```
```
λ mc admin decommission status alias/ http://minio{1...2}/data{1...4}
Progress: ===================> [1GiB/sec] [15%] [4TiB/50TiB]
Time Remaining: 4 hours (started 3 hours ago)
```
```
λ mc admin decommission status alias/ http://minio{1...2}/data{1...4}
ERROR: This pool is not scheduled for decommissioning currently.
```
```
λ mc admin decommission cancel alias/
┌─────┬─────────────────────────────────┬──────────────────────────────────┬──────────┐
│ ID │ Pools │ Capacity │ Status │
│ 1st │ http://minio{1...2}/data{1...4} │ 439 GiB (used) / 561 GiB (total) │ Draining │
└─────┴─────────────────────────────────┴──────────────────────────────────┴──────────┘
```
> NOTE: Canceled decommission will not make the pool active again, since we might have
> Potentially partial duplicate content on the other pools, to avoid this scenario be
> very sure to start decommissioning as a planned activity.
```
λ mc admin decommission cancel alias/ http://minio{1...2}/data{1...4}
┌─────┬─────────────────────────────────┬──────────────────────────────────┬────────────────────┐
│ ID │ Pools │ Capacity │ Status │
│ 1st │ http://minio{1...2}/data{1...4} │ 439 GiB (used) / 561 GiB (total) │ Draining(Canceled) │
└─────┴─────────────────────────────────┴──────────────────────────────────┴────────────────────┘
```
Harshavardhana
Krishna Srinivas