This PR makes a feasible approach to handle all the scenarios
that we must face to avoid returning "panic."
Instead, we must return "errServerNotInitialized" when a
bucketMetadataSys.Get() is called, allowing the caller to
retry their operation and wait.
Bonus fix the way data-usage-cache stores the object.
Instead of storing usage-cache.bin with the bucket as
`.minio.sys/buckets`, the `buckets` must be relative
to the bucket `.minio.sys` as part of the object name.
Otherwise, there is no way to decommission entries at
`.minio.sys/buckets` and their final erasure set positions.
A bucket must never have a `/` in it. Adds code to read()
from existing data-usage.bin upon upgrade.
Currently we have IOPs of these patterns
```
[OS] os.Mkdir play.min.io:9000 /disk1 2.718µs
[OS] os.Mkdir play.min.io:9000 /disk1/data 2.406µs
[OS] os.Mkdir play.min.io:9000 /disk1/data/.minio.sys 4.068µs
[OS] os.Mkdir play.min.io:9000 /disk1/data/.minio.sys/tmp 2.843µs
[OS] os.Mkdir play.min.io:9000 /disk1/data/.minio.sys/tmp/d89c8ceb-f8d1-4cc6-b483-280f87c4719f 20.152µs
```
It can be seen that we can save quite Nx levels such as
if your drive is mounted at `/disk1/minio` you can simply
skip sending an `Mkdir /disk1/` and `Mkdir /disk1/minio`.
Since they are expected to exist already, this PR adds a way
for us to ignore all paths upto the mount or a directory which
ever has been provided to MinIO setup.
a/b/c/d/ where `a/b/c/` exists results in additional syscalls
such as an Lstat() call to verify if the `a/b/c/` exists
and its a directory.
We do not need to do this on MinIO since the parent prefixes
if exist, we can simply return success without spending
additional syscalls.
Also this implementation attempts to simply use Access() calls
to avoid os.Stat() calls since the latter does memory allocation
for things we do not need to use.
Access() is simpler since we have a predictable structure on
the backend and we know exactly how our path structures are.
dataDir loosely based on maxima is incorrect and does not
work in all situations such as disks in the following order
- xl.json migration to xl.meta there may be partial xl.json's
leftover if some disks are not yet connected when the disk
is yet to come up, since xl.json mtime and xl.meta is
same the dataDir maxima doesn't work properly leading to
quorum issues.
- its also possible that XLV1 might be true among the disks
available, make sure to keep FileInfo based on common quorum
and skip unexpected disks with the older data format.
Also, this PR tests upgrade from older to a newer release if the
data is readable and matches the checksum.
NOTE: this is just initial work we can build on top of this to do further tests.
gracefully start the server, if there are other drives
available - print enough information for administrator
to notice the errors in console.
Bonus: for really large streams use larger buffer for
writes.
There is a disparency of behavior under Linux & Windows about
the returned error when trying to rename a non existant path.
err := os.Rename("/path/does/not/exist", "/tmp/copy")
Linux:
isSysErrNotDir(err) = false
os.IsNotExist(err) = true
Windows:
isSysErrNotDir(err) = true
os.IsNotExist(err) = true
ENOTDIR in Linux is returned when the destination path
of the rename call contains a file in one of the middle
segments of the path (e.g. /tmp/file/dst, where /tmp/file
is an actual file not a directory)
However, as shown above, Windows has more scenarios when
it returns ENOTDIR. For example, when the source path contains
an inexistant directory in its path.
In that case, we want errFileNotFound returned and not
errFileAccessDenied, so this commit will add a further check to close
the disparency between Windows & Linux.
Calling ListMultipartUploads fails if an upload is aborted while a
part is being uploaded because the directory for the upload exists
(since fsRenameFile ends up calling os.MkdirAll) but the meta JSON file
doesn't. To fix this we make sure an upload hasn't been aborted during
PutObjectPart by checking the existence of the directory for the upload
while moving the temporary part file into it.
In scenario 1
```
- bucket/object-prefix
- bucket/object-prefix/object
```
Server responds with `XMinioParentIsObject`
In scenario 2
```
- bucket/object-prefix/object
- bucket/object-prefix
```
Server responds with `XMinioObjectExistsAsDirectory`
Fixes#6566
Under any concurrent removeObjects in progress
might have removed the parents of the same prefix
for which there is an ongoing putObject request.
An inconsistent situation may arise as explained
below even under sufficient locking.
PutObject is almost successful at the last stage when
a temporary file is renamed to its actual namespace
at `a/b/c/object1`. Concurrently a RemoveObject is
also in progress at the same prefix for an `a/b/c/object2`.
To create the object1 at location `a/b/c` PutObject has
to create all the parents recursively.
```
a/b/c - os.MkdirAll loops through has now created
'a/' and 'b/' about to create 'c/'
a/b/c/object2 - at this point 'c/' and 'object2'
are deleted about to delete b/
```
Now for os.MkdirAll loop the expected situation is
that top level parent 'a/b/' exists which it created
, such that it can create 'c/' - since removeObject
and putObject do not compete for lock due to holding
locks at different resources. removeObject proceeds
to delete parent 'b/' since 'c/' is not yet present,
once deleted 'os.MkdirAll' would receive an error as
syscall.ENOENT which would fail the putObject request.
This PR tries to address this issue by implementing
a safer/guarded approach where we would retry an operation
such as `os.MkdirAll` and `os.Rename` if both operations
observe syscall.ENOENT.
Fixes#5254
Harshavardhana
Ritesh H Shukla
Anis Elleuch
Daryl Finlay
kannappanr
Oleg Kovalov