- Changes related to moving admin APIs
- admin APIs now have an endpoint under /minio/admin
- admin APIs are now versioned - a new API to server the version is
added at "GET /minio/admin/version" and all API operations have the
path prefix /minio/admin/v1/<operation>
- new service stop API added
- credentials change API is moved to /minio/admin/v1/config/credential
- credentials change API and configuration get/set API now require TLS
so that credentials are protected
- all API requests now receive JSON
- heal APIs are disabled as they will be changed substantially
- Heal API changes
Heal API is now provided at a single endpoint with the ability for a
client to start a heal sequence on all the data in the server, a
single bucket, or under a prefix within a bucket.
When a heal sequence is started, the server returns a unique token
that needs to be used for subsequent 'status' requests to fetch heal
results.
On each status request from the client, the server returns heal result
records that it has accumulated since the previous status request. The
server accumulates upto 1000 records and pauses healing further
objects until the client requests for status. If the client does not
request any further records for a long time, the server aborts the
heal sequence automatically.
A heal result record is returned for each entity healed on the server,
such as system metadata, object metadata, buckets and objects, and has
information about the before and after states on each disk.
A client may request to force restart a heal sequence - this causes
the running heal sequence to be aborted at the next safe spot and
starts a new heal sequence.
This change replaces all imports of "crypto/sha256" with
"github.com/minio/sha256-simd". The sha256-simd package
is faster on ARM64 (NEON instructions) and can take advantage
of AVX-512 in certain scenarios.
Fixes#5374
This change restircts the supported cipher suites of the minio server.
The server only supports AEAD ciphers (Chacha20Poly1305 and
AES-GCM)
The supported cipher suites are:
- tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305
- tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305
- tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
- tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
- tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
- tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
Fixes#5244 and #5291
After the addition of Storage Class support, readQuorum
and writeQuorum are decided on a per object basis, instead
of deployment wide static quorums.
This PR updates madmin api to remove readQuorum/writeQuorum
and add Standard storage class and reduced redundancy storage
class parity as return values. Since these parity values are
used to decide the quorum for each object.
Fixes#5378
Since the server performs automatic clean-up of multipart uploads that
have not been resumed for more than a couple of weeks, it was decided
to remove functionality to heal multipart uploads.
- Use it to send the Content-MD5 header correctly encoded to S3
Gateway
- Fixes a bug in PutObject (including anonymous PutObject) and
PutObjectPart with S3 Gateway found when testing with Mint.
This change adds server-side-encryption support for HEAD, GET and PUT
operations. This PR only addresses single-part PUTs and GETs without
HTTP ranges.
Further this change adds the concept of reserved object metadata which is required
to make encrypted objects tamper-proof and provide API compatibility to AWS S3.
This PR adds the following reserved metadata entries:
- X-Minio-Internal-Server-Side-Encryption-Iv ('guarantees' tamper-proof property)
- X-Minio-Internal-Server-Side-Encryption-Kdf (makes Key-MAC computation negotiable in future)
- X-Minio-Internal-Server-Side-Encryption-Key-Mac (provides AWS S3 API compatibility)
The prefix `X-Minio_Internal` specifies an internal metadata entry which must not
send to clients. All client requests containing a metadata key starting with `X-Minio-Internal`
must also rejected. This is implemented by a generic-handler.
This PR implements SSE-C separated from client-side-encryption (CSE). This cannot decrypt
server-side-encrypted objects on the client-side. However, clients can encrypted the same object
with CSE and SSE-C.
This PR does not address:
- SSE-C Copy and Copy part
- SSE-C GET with HTTP ranges
- SSE-C multipart PUT
- SSE-C Gateway
Each point must be addressed in a separate PR.
Added to vendor dir:
- x/crypto/chacha20poly1305
- x/crypto/poly1305
- github.com/minio/sio
When MINIO_TRACE_DIR is provided, create a new log file and store all
HTTP requests + responses data, body are excluded to reduce memory
consumption. MINIO_HTTP_TRACE=1 enables logging. Use non mem
consuming http req/resp recorders, the maximum is about 32k per request.
This logs to STDOUT, body logging is disabled for PutObject PutObjectPart
GetObject.
Verify() was being called by caller after the data
has been successfully read after io.EOF. This disconnection
opens a race under concurrent access to such an object.
Verification is not necessary outside of Read() call,
we can simply just do checksum verification right inside
Read() call at io.EOF.
This approach simplifies the usage.
This PR addresses a long standing dependency on
`gopkg.in/check.v1` project used for our tests.
All tests are re-written to use the go default
testing framework instead.
There was no reason for us to use an external
package where Go tools are sufficient for this.
The reedsolomon library now avoids allocations during reconstruction.
This change exploits that to reduce memory allocs and GC preasure during
healing and reading.
On *NIX platforms the statfs(2) system call returns a struct containing both the
free blocks in the filesystem (Statfs_t.Bfree) and the free blocks available to
the unprivileged or non-superuser (Statfs_t.Bavail).
The `Bfree` and `Bavail` fields (with `Bfree >= Bavail`) will be set to
different values on e.g. filesystems such as ext4 that reserve a certain
percentage of the filesystem blocks which may only be allocated by admnistrative
privileged processes.
The calculations for the `Total` disk space need to subtract the difference
between the `Bfree` and `Bavail` fields for it to correctly show the total
available storage space available for unprivileged users.
This implicitly fixes a bug where the `Used = Total - Free` calculation yielded
different (and also incorrect) results for identical contents stored when only
the sizes of the disks or backing volumes differed. (as can be witnessed in the
`Used:` value displayed in the Minio browser)
See:
- https://wiki.archlinux.org/index.php/ext4#Reserved_blocks
- http://man7.org/linux/man-pages/man2/statfs.2.html
- https://man.openbsd.org/statfs
- http://lingrok.org/xref/coreutils/src/df.c#893
This is an improvement upon existing implementation
by avoiding transfer of access and secret keys over
the network. This change only exchanges JWT tokens
generated by an rpc client. Even if the JWT can be
traced over the network on a non-TLS connection, this
change makes sure that we never really expose the
secret key over the network.
Since go1.8 os.RemoveAll and os.MkdirAll both support long
path names i.e UNC path on windows. The code we are carrying
was directly borrowed from `pkg/os` package and doesn't need
to be in our repo anymore. As a side affect this also
addresses our codecoverage issue.
Refer #4658
Peek could fail legitimately when clients abruptly close connection. So,
io.EOF and network timeout errors are not logged while all other errors
will be logged.
* Refactor HTTP server to address bugs
* Remove unnecessary goroutine to start multiple TCP listeners.
* HTTP server waits for shutdown to maximum of Server.ShutdownTimeout
than per serverShutdownPoll.
* Handles new connection errors properly.
* Handles read and write timeout properly.
* Handles error on start of HTTP server properly by exiting minio
process.
Fixes#4494#4476 & fixed review comments
This updates dependency for
- AWS S3 backend.
- pkg/madmin
```
- Relax isValidBucketName to allow reading existing buckets. (#708) (3 minutes ago) <Harshavardhana>
- For GCS the size limit of S3 is not useful. (#711) (3 days ago) <Harshavardhana>
- s3utils: Support AWS S3 US GovCloud endpoint. (#701) (3 days ago) <Harshavardhana>
- api: Always strip 80/443 port from host (#709) (3 days ago) <Anis Elleuch>
- Redact signature strings properly. (#706) (4 days ago) <Harshavardhana>
- api: Single putObject can use temporary file always. (#703) (6 days ago) <Harshavardhana>
- Spelling fix (#704) (7 days ago) <Jacob Taylor>
- api/encrypt: Get() on encrypted object should be a reader. (#699) (2 weeks ago) <Harshavardhana>
- get: Fix reading an object if its size is unknown (#694) (3 weeks ago) <Anis Elleuch>
- fixes#696 by updating the examples for put-encrypted-object and get-encrypted-object (#697) (3 weeks ago) <Tejay Cardon>
- fix InvalidAccessKeyId error according to amazon documentation (#692) (4 weeks ago) <samkevich>
- Add AWS S3 SSE-C example. (#689) (4 weeks ago) <Harshavardhana>
- According to RFC7232 Etag should be in quotes for If-Match. (#688) (5 weeks ago) <Harshavardhana>
- api: getReaderSize() should honor seeked file descriptors. (#681) (5 weeks ago) <Harshavardhana>
- tests: Use bytes.Repeat() when generating big data (#683) (5 weeks ago) <Anis Elleuch>
- api: Failed call retry with region only when http.StatusBadRequest. (#678) (5 weeks ago) <Harshavardhana>
- api: Add NewWithCredentials() (#646) (5 weeks ago) <Harshavardhana>
```
Looks like if we follow pattern such as
```
_ = rlk
```
Go can potentially kick in GC and close the fd when
the reference is lost, only speculation is that
the cause here is `SetFinalizer` which is set on
`os.close()` internally in `os` stdlib.
This is unexpected and unsual endeavour for Go, but
we have to make sure the reference is never lost
and always dies with the server.
Fixes#4530
This patch also reverts previous changes which were
merged for migration to the newer disk format. We will
be bringing these changes in subsequent releases. But
we wish to add protection in this release such that
future release migrations are protected.
Revert "fs: Migration should handle bucketConfigs as regular objects. (#4482)"
This reverts commit 976870a391.
Revert "fs: Migrate object metadata to objects directory. (#4195)"
This reverts commit 76f4f20609.
This change adopts the upstream fix in this regard at
https://go-review.googlesource.com/#/c/41834/ for Minio's
purposes.
Go's current os.Stat() lacks support for lot of strange
windows files such as
- share symlinks on SMB2
- symlinks on docker nanoserver
- de-duplicated files on NTFS de-duplicated volume.
This PR attempts to incorporate the change mentioned here
https://blogs.msdn.microsoft.com/oldnewthing/20100212-00/?p=14963/
The article suggests to use Windows I/O manager to
dereference the symbolic link.
Fixes#4122
Duration for which a lock was held can be computed from the `Since`
field of `OpsLockState`. It is the difference between current time and
time at which the namespace lock was held. This change avoids
superfluous instrumentation.
Previous value was set to avoid large cache value build
up but we can clearly see this can cause lots of GC
pauses which can lead to significant drop in performance.
Change this value to 50% and decrease the value to 25%
once the 75% cache size is used. To have a larger
window for GC pauses.
Another change is to only allow caching if a server has
more than 24GB of RAM instead of 8GB.
go fails to build Minio under at least, armv6 and 386 due to some
inconsistencies in the type of one syscall variable in different
architectures. This PR casts that variable to uint64 to achieve
the desired consistency.
This is necessary where in certain environments where
cgroup is used to limit memory usage of a container or
a particular process.
GetStats() is used by caching module to figure out the
optimal cacheable size in memory with cgroup limits
what sysinfo reports might not be the right value set
for a given process.
Fixes#4001
`disksUnavailable` healStatus constant indicates that a given object
needs healing but one or more of disks requiring heal are offline. This
can be used by admin heal API consumers to distinguish between a
successful heal and a no-op since the outdated disks were offline.
In the algorithm to check if an object requires healing, in addition to
checking if all disks have xl.json present we should check if all parts
of the object are present and have valid blake2b checksums.
Also fixed a minor compilation error in heal-objects-list.go.
* Add a new function Save() which saves given configuration into given file.
* Simplify Load() function.
* Remove unused CheckVersion().
* CheckData() is a private function now.
* quick_test.go is part of quick package now.
* minio server uses top level quick.Load() and quick.Save() functions.
Without this fix, `mc admin heal -I` wouldn't be able to heal ongoing
uploads. `mc` depends on `ListUploadsHeal` API to identify ongoing
uploads to heal given a bucket and an object.
This API is meant for administrative tools like mc-admin to heal an
ongoing multipart upload on a Minio server. N B This set of admin
APIs apply only for Minio servers.
`github.com/minio/minio/pkg/madmin` provides a go SDK for this (and
other admin) operations. Specifically,
func HealUpload(bucket, object, uploadID string, dryRun bool) error
Sample admin API request:
POST
/?heal&bucket=mybucket&object=myobject&upload-id=myuploadID&dry-run
- Header(s): ["x-minio-operation"] = "upload"
Notes:
- bucket, object and upload-id are mandatory query parameters
- if dry-run is set, API returns success if all parameters passed are
valid.
Following is a sample list lock API request schematic,
/?lock&bucket=mybucket&prefix=myprefix&duration=holdDuration
x-minio-operation: list
The response would contain the list of locks held on mybucket matching
myprefix for a duration longer than holdDuration.
The order of marker and delimiter and in listObjectsHeal() internal function
are switched. That will give wrong result in case of a non recursive objects
heal list.
* Implement heal format REST API handler
* Implement admin peer rpc handler to re-initialize storage
* Implement HealFormat API in pkg/madmin
* Update pkg/madmin API.md to incl. HealFormat
* Added unit tests for ReInitDisks rpc handler and HealFormatHandler
* Filter lock info based on bucket, prefix and time since lock was held
* Implement list and clear locks REST API
* madmin: Add list and clear locks API
* locks: Clear locks matching bucket, prefix, relTime.
* Gather lock information across nodes for both list and clear locks admin REST API.
* docs: Add lock API to management APIs
This change brings in changes at multiple places
- Reuse buffers at almost all locations ranging
from rpc, fs, xl, checksum etc.
- Change caching behavior to disable itself
under low memory conditions i.e < 8GB of RAM.
- Only objects cached are of size 1/10th the size
of the cache for example if 4GB is the cache size
the maximum object size which will be cached
is going to be 400MB. This change is an
optimization to cache more objects rather
than few larger objects.
- If object cache is enabled default GC
percent has been reduced to 20% in lieu
with newly found behavior of GC. If the cache
utilization reaches 75% of the maximum value
GC percent is reduced to 10% to make GC
more aggressive.
- Do not use *bytes.Buffer* due to its growth
requirements. For every allocation *bytes.Buffer*
allocates an additional buffer for its internal
purposes. This is undesirable for us, so
implemented a new cappedWriter which is capped to a
desired size, beyond this all writes rejected.
Possible fix for #3403.
Do not attempt to fetch volume/drive information for
each i/o situation. In our case we do this in all calls
`posix.go` this in-turn created a terrible situation for
windows. This issue does not affect the i/o path on Unix
platforms since statvfs calls are in the range of micro
seconds on these platforms.
This verification is only needed during startup and we
let things fail at a later stage on windows.
This API is precursor before implementing `minio lambda` and `mc` continous replication.
This new api is an extention to BucketNofication APIs.
// Request
```
GET /bucket?notificationARN=arn:minio:lambda:us-east-1:10:minio HTTP/1.1
...
...
```
// Response
```
{"Records": ...}
...
...
...
{"Records": ...}
```
- Support for '?' wildcard for resource matching.
- Wildcard package is added with Match functions.
- Wildcard.Match supports '*' and wild.MatchExtended supports both '*'
and '?' wildcards in the pattern string.
- Tests for the same for the wide range of cases.
* XL/erasure-read: optimize memory allocation during erasure-read by using temporary buffer pool.
With the change the buffer needed during GetObject by erasureReadFile is allocated only once.
Change brings in a new signVerifyReader which provides a io.Reader
compatible reader, additionally implements Verify() function.
Verify() function validates the signature present in the incoming
request. This approach is choosen to avoid complexities involved
in using io.Pipe().
Thanks to Krishna for his inputs on this.
Fixes#2058Fixes#2054Fixes#2087
Previously checkDiskFree() checks for free available space. This
patch enables checkDiskFree() also checks for free inodes in linux and
free clusters in windows.
Fixes#2075
The object cache implementation is XL cache, which defaults
to 8GB worth of read cache. Currently GetObject() transparently
writes to this cache upon first client read and then subsequently
serves reads from the same cache.
Currently expiration is not implemented.
Some environments might disable access to `/dev/tty`, fall
back to '80' in such scenarios.
Move to 'cheggaaa/pb' package for better cross platform
support on fetching terminal width.
Fixes#1891
The functionality provided by minhttp will be implemented
cleanly through our own APIs. Since we are not going to
send SIGUSR2 and manage configuration in that manner, it
doesn't make sense to use minhttp.
Fixes#1586
Signature calculation has now moved out from being a package to
top-level as a layered mechanism.
In case of payload calculation with body, go-routines are initiated
to simultaneously write and calculate shasum. Errors are sent
over the writer so that the lower layer removes the temporary files
properly.
Optimizing List Objects by using binary sort to discard entries in cases
where prefix or marker is set.
Adding test coverage to ListObjects.
Adding benchmark to ListObjects.
In the common case, GetObject is called on a bucket that exists and an
object that exists and is not a directory. It should be optimized for
this case, thus error-related syscalls are pushed back until they are
necessary.
This should not impact performance negatively in the uncommon case, and
instead drops two otherwise unnecessary os.Stat's in the common case.
The race conditions around a proper error being returned were present
beforehand.
It also renames 'err' to 'e'.
When list object is invoked, it creates a goroutine if not available
for given parameters else uses existing goroutine. These goroutines
are alive for 15 seconds for further continuation list object request
else they exit.
Fixes#1076
This commit improves the docs for both functions (more Go-like) and
drops an unnecessary condition in IsValidBucketName. This also drops a
condition in IsValidObjectName where "" (empty string) was a valid
object name. This has been fixed and will no longer return true.
This commit also adds tests for both functions, including a regression
test for the bug fix.
There is now a simple test and a benchmark for ListBuckets. I also
dropped an unnecessary check that was simply repeated from above,
guaranteed to be true.
It had a lot of code that was the same as GetBucketMetadata, so instead
call GBM from SBM so as to reduce doing the same thing in two different
spots. Theoretically this will induce a small overhead as now at least
two calls of denormalizeBucket are made, although this shouldn't be
noticeable.
This commit prefers the use of 'defer' for fs.Unlock (and fs.RUnlock)
because it is more idiomatic Go and reduces repetition in the code,
lending to a cleaner code base.
It also switches a few uses of the lock to read-only locks, which should
improve performance of those functions dramatically in certain contexts.
This API takes input XML input in following form.
```
<?xml version="1.0" encoding="UTF-8"?>
<Delete>
<Quiet>true</Quiet>
<Object>
<Key>Key</Key>
</Object>
<Object>
<Key>Key</Key>
</Object>
...
</Delete>
```
and responds the list of successful deletes, list of errors
for all the deleted objects.
```
<?xml version="1.0" encoding="UTF-8"?>
<DeleteResult xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
<Deleted>
<Key>sample1.txt</Key>
</Deleted>
<Error>
<Key>sample2.txt</Key>
<Code>AccessDenied</Code>
<Message>Access Denied</Message>
</Error>
</DeleteResult>
```
Golang 1.6 is default version for the build now.
Additionally set 'GODEBUG=cgocheck=0' for now, until
we fix the erasure coding package.
Readmore here https://tip.golang.org/doc/go1.6#cgo
- Move fs-definitions.go and break them into fs-datatypes.go, fs-bucket-acl.go
and fs-utils.go
- Move api-definitions.go to api-response.go, where they should be.
- Move web-definitions to its related handlers.
Minor optimization.
- Add 1000 entries buffered channel for walkerCh.
- Reset marker after the lexical order has reached and
compare only if the marker is set.
- Fixes initiating parallel uploads, and configs being quickly
re-written by another incoming request.
- Parallel uploads work smoothly now and return expected behavior.
Fail createObject() if a file already exists and one attempts
to create a prefix/directory by same name.
Send an approriate error back to the client as 409 Conflict.
Currently the server would set 'application/octet-stream' for all
objects, set this value based on the file extension transparently.
This is useful in case of minio browser to facilitate displaying
proper icons for the different mime data types.
Incoming request params in presigned can come in different order
for different implementations. Rather than verifying a full string
we should verify individual params instead.
This patch fixes an incompatibility issue with AWS SDK Java.
Fixes#1059 - Thanks to @notnoopci for reporting this problem.
listObjects was returning inconsistent results, i.e missing
entries during recursive and non-recursive listing. This led
to 'mc mirror' copying contents repeatedly consisdering
these files to be missing on the destination.
This patch addresses this problem - fixes#1056
HMAC is a much simpler implementation, providing the same
benefits as RSA, avoids additional steps and keeps the code
simpler.
This patch also additionally
- Implements PutObjectURL API.
- GetObjectURL, PutObjectURL take TargetHost as another
argument for generating URL's for proper target destination.
- Adds experimental TLS support for JSON RPC calls.
Without this change listObjects() goes into an infinite loop for
files which have special characters i.e "++" encoded with "%2B%2B".
We have to unescape and convert them to their native representation
before being used internally.
Fixes#1052
Existing code
```
{
if os.IsNotExist(e) {
e = os.MkdirAll(objectDir, 0700)
if e != nil {
return "", probe.NewError(e)
}
}
return "", probe.NewError(e) ---> Error was here.
}
```
For a successful 'MkdirAll' it would still return an empty uploadID,
but the 'error' would be nil. This would succeed the request but
client would fail.
Fix is to re-arrange the logic. Thanks to Alexander Neumann @fd0, for
reporting this problem.
- limit list buckets to limit only 100 buckets, all uppercase buckets
are now lowercase and work transparently with all calls.
- Change disk.Stat to disk.GetInfo and return back disk.Info{} struct.
- Introduce new ioutils package which implements ReadDirN(path, n),
ReadDirNamesN(path, n)
Golang http server strips off 'Expect' header, if the
client sent this as part of signed headers we need to
handle otherwise we would see a signature mismatch.
`aws-cli` sets this as part of signed headers which is
a bad idea since servers trying to implement AWS
Signature version '4' will all encounter this issue.
According to
http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.20
Expect header is always of form:
Expect = "Expect" ":" 1#expectation
expectation = "100-continue" | expectation-extension
So it safe to assume that '100-continue' is what would
be sent, for the time being keep this work around.
Remove option of providing Technique and handling errors based on that
choose a matrix type automatically based on number of data blocks.
INTEL recommends on using cauchy for consistent invertible matrices,
while vandermonde is faster we should default to cauchy for large
data blocks.
Stream reading needs to check for length parameter being non zero,
after Reading() a predefined set of buffer length an EOF might be returned
with length == 0.
Erasure taking this zeroed data in might wrongly encode it as part of existing
data blocks which leads to errors while decoding even when the other contents
are intact.
- Upon first time invocation ``minio controller`` would create access keys and secret id
- Upon request passing 'keys' arg ``minio controller`` would provide the keys
- Add colorized notification
This change brings a new SignatureHandler where Presigned.
Requests without Payload are handled very early before even
going through the call.
This change simplifies Donut codebase to not have signature related
logic for all API's.
Simplification is still needed for Payload based signature eg. PUT/POST calls
, which are still part of the donut codebase, which will be done subsequently
after donut re-write.
Calling multiple times TestingT{} will hook up runner for Suites for that many times
which would lead to repeated running tests.
Fix it by only initializing it once for all the Suites
- over the course of a project history every maintainer needs to update
its dependency packages, the problem essentially with godep is manipulating
GOPATH - this manipulation leads to static objects created at different locations
which end up conflicting with the overall functionality of golang.
This also leads to broken builds. There is no easier way out of this other than
asking developers to do 'godep restore' all the time. Which perhaps as a practice
doesn't sound like a clean solution. On the other hand 'godep restore' has its own
set of problems.
- govendor is a right tool but a stop gap tool until we wait for golangs official
1.5 version which fixes this vendoring issue once and for all.
- govendor provides consistency in terms of how import paths should be handled unlike
manipulation GOPATH.
This has advantages
- no more compiled objects being referenced in GOPATH and build time GOPATH
manging which leads to conflicts.
- proper import paths referencing the exact package a project is dependent on.
govendor is simple and provides the minimal necessary tooling to achieve this.
For now this is the right solution.
This convenience was necessary to be used for golang library functions like io.Copy and io.Pipe
where we shouldn't be writing proxies and alternatives returning *probe.Error
This change also brings more changes across code base for clear separation regarding where an error
interface should be passed encapsulating *probe.Error and where it should be used as is.
- Explicitly cast statfs_t members to int64 (this structure is
platform-specific)
- Add pass-through New methods to Darwin SHA package
- Move scsi pkg types to common translation unit (package was empty)
- Add stub implementations mount/disk ops for OS X
Just like how http.Handlers can be overlayed on top of each other
with each implementing ServeHTTP().
drivers.Driver can be overlayed on top of each other in similar manner
which would implement the drivers.Driver interface.
API <----> cache <----> donut <----> donut(format)
This largely avoids a large buffer copy which would accumulate inside proxyReader{}
This patch also implements "initialize()" function to init and populate data
on all the existing buckets, avoiding the redundant ListBuckets() invoked by
every API call.