when source and destination are same and versioning is enabled
on the destination bucket - we do not need to re-create the entire
object once again to optimize on space utilization.
Cases this PR is not supporting
- any pre-existing legacy object will not
be preserved in this manner, meaning a new
dataDir will be created.
- key-rotation and storage class changes
of course will never re-use the dataDir
conflicting files can exist on FS at
`.minio.sys/buckets/testbucket/policy.json/`, this is an
expected valid scenario for FS mode allow it to work,
i.e ignore and move forward
With reduced parity our write quorum should be same
as read quorum, but code was still assuming
```
readQuorum+1
```
In all situations which is not necessary.
Generalize replication target management so
that remote targets for a bucket can be
managed with ARNs. `mc admin bucket remote`
command will be used to manage targets.
Context timeout might race on each other when timeouts are lower
i.e when two lock attempts happened very quickly on the same resource
and the servers were yet trying to establish quorum.
This situation can lead to locks held which wouldn't be unlocked
and subsequent lock attempts would fail.
This would require a complete server restart. A potential of this
issue happening is when server is booting up and we are trying
to hold a 'transaction.lock' in quick bursts of timeout.
replace dummy buffer with nullReader{} instead,
to avoid large memory allocations in memory
constrainted environments. allows running
obd tests in such environments.
Currently, listing directories on HDFS incurs a per-entry remote Stat() call
penalty, the cost of which can really blow up on directories with many
entries (+1,000) especially when considered in addition to peripheral
calls (such as validation) and the fact that minio is an intermediary to the
client (whereas other clients listed below can query HDFS directly).
Because listing directories this way is expensive, the Golang HDFS library
provides the [`Client.Open()`] function which creates a [`FileReader`] that is
able to batch multiple calls together through the [`Readdir()`] function.
This is substantially more efficient for very large directories.
In one case we were witnessing about +20 seconds to list a directory with 1,500
entries, admittedly large, but the Java hdfs ls utility as well as the HDFS
library sample ls utility were much faster.
Hadoop HDFS DFS (4.02s):
λ ~/code/minio → use-readdir
» time hdfs dfs -ls /directory/with/1500/entries/
…
hdfs dfs -ls 5.81s user 0.49s system 156% cpu 4.020 total
Golang HDFS library (0.47s):
λ ~/code/hdfs → master
» time ./hdfs ls -lh /directory/with/1500/entries/
…
./hdfs ls -lh 0.13s user 0.14s system 56% cpu 0.478 total
mc and minio **without** optimization (16.96s):
λ ~/code/minio → master
» time mc ls myhdfs/directory/with/1500/entries/
…
./mc ls 0.22s user 0.29s system 3% cpu 16.968 total
mc and minio **with** optimization (0.40s):
λ ~/code/minio → use-readdir
» time mc ls myhdfs/directory/with/1500/entries/
…
./mc ls 0.13s user 0.28s system 102% cpu 0.403 total
[`Client.Open()`]: https://godoc.org/github.com/colinmarc/hdfs#Client.Open
[`FileReader`]: https://godoc.org/github.com/colinmarc/hdfs#FileReader
[`Readdir()`]: https://godoc.org/github.com/colinmarc/hdfs#FileReader.Readdir
If there are many listeners to bucket notifications or to the trace
subsystem, healing fails to work properly since it suspends itself when
the number of concurrent connections is above a certain threshold.
These connections are also continuous and not costly (*no disk access*),
it is okay to just ignore them in waitForLowHTTPReq().
this is to detect situations of corruption disk
format etc errors quickly and keep the disk online
in such scenarios for requests to fail appropriately.
String x might contain trimming spaces. And it needs to be trimmed. For
example, in csv files, there might be trimming spaces in a field that
ought to meet a query condition that contains the value without
trimming spaces. This applies to both intCast and floatCast functions.
