syncthing/vendor/github.com/minio/minio-go/hook-reader.go
Jakob Borg 916ec63af6 cmd/stdiscosrv: New discovery server (fixes #4618)
This is a new revision of the discovery server. Relevant changes and
non-changes:

- Protocol towards clients is unchanged.

- Recommended large scale design is still to be deployed nehind nginx (I
  tested, and it's still a lot faster at terminating TLS).

- Database backend is leveldb again, only. It scales enough, is easy to
  setup, and we don't need any backend to take care of.

- Server supports replication. This is a simple TCP channel - protect it
  with a firewall when deploying over the internet. (We deploy this within
  the same datacenter, and with firewall.) Any incoming client announces
  are sent over the replication channel(s) to other peer discosrvs.
  Incoming replication changes are applied to the database as if they came
  from clients, but without the TLS/certificate overhead.

- Metrics are exposed using the prometheus library, when enabled.

- The database values and replication protocol is protobuf, because JSON
  was quite CPU intensive when I tried that and benchmarked it.

- The "Retry-After" value for failed lookups gets slowly increased from
  a default of 120 seconds, by 5 seconds for each failed lookup,
  independently by each discosrv. This lowers the query load over time for
  clients that are never seen. The Retry-After maxes out at 3600 after a
  couple of weeks of this increase. The number of failed lookups is
  stored in the database, now and then (avoiding making each lookup a
  database put).

All in all this means clients can be pointed towards a cluster using
just multiple A / AAAA records to gain both load sharing and redundancy
(if one is down, clients will talk to the remaining ones).

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4648
2018-01-14 08:52:31 +00:00

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Go

/*
* Minio Go Library for Amazon S3 Compatible Cloud Storage
* Copyright 2015-2017 Minio, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package minio
import "io"
// hookReader hooks additional reader in the source stream. It is
// useful for making progress bars. Second reader is appropriately
// notified about the exact number of bytes read from the primary
// source on each Read operation.
type hookReader struct {
source io.Reader
hook io.Reader
}
// Seek implements io.Seeker. Seeks source first, and if necessary
// seeks hook if Seek method is appropriately found.
func (hr *hookReader) Seek(offset int64, whence int) (n int64, err error) {
// Verify for source has embedded Seeker, use it.
sourceSeeker, ok := hr.source.(io.Seeker)
if ok {
return sourceSeeker.Seek(offset, whence)
}
// Verify if hook has embedded Seeker, use it.
hookSeeker, ok := hr.hook.(io.Seeker)
if ok {
return hookSeeker.Seek(offset, whence)
}
return n, nil
}
// Read implements io.Reader. Always reads from the source, the return
// value 'n' number of bytes are reported through the hook. Returns
// error for all non io.EOF conditions.
func (hr *hookReader) Read(b []byte) (n int, err error) {
n, err = hr.source.Read(b)
if err != nil && err != io.EOF {
return n, err
}
// Progress the hook with the total read bytes from the source.
if _, herr := hr.hook.Read(b[:n]); herr != nil {
if herr != io.EOF {
return n, herr
}
}
return n, err
}
// newHook returns a io.ReadSeeker which implements hookReader that
// reports the data read from the source to the hook.
func newHook(source, hook io.Reader) io.Reader {
if hook == nil {
return source
}
return &hookReader{source, hook}
}