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51aa59a737
This PR adds a WebSocket grid feature that allows servers to communicate via
a single two-way connection.
There are two request types:
* Single requests, which are `[]byte => ([]byte, error)`. This is for efficient small
roundtrips with small payloads.
* Streaming requests which are `[]byte, chan []byte => chan []byte (and error)`,
which allows for different combinations of full two-way streams with an initial payload.
Only a single stream is created between two machines - and there is, as such, no
server/client relation since both sides can initiate and handle requests. Which server
initiates the request is decided deterministically on the server names.
Requests are made through a mux client and server, which handles message
passing, congestion, cancelation, timeouts, etc.
If a connection is lost, all requests are canceled, and the calling server will try
to reconnect. Registered handlers can operate directly on byte
slices or use a higher-level generics abstraction.
There is no versioning of handlers/clients, and incompatible changes should
be handled by adding new handlers.
The request path can be changed to a new one for any protocol changes.
First, all servers create a "Manager." The manager must know its address
as well as all remote addresses. This will manage all connections.
To get a connection to any remote, ask the manager to provide it given
the remote address using.
```
func (m *Manager) Connection(host string) *Connection
```
All serverside handlers must also be registered on the manager. This will
make sure that all incoming requests are served. The number of in-flight
requests and responses must also be given for streaming requests.
The "Connection" returned manages the mux-clients. Requests issued
to the connection will be sent to the remote.
* `func (c *Connection) Request(ctx context.Context, h HandlerID, req []byte) ([]byte, error)`
performs a single request and returns the result. Any deadline provided on the request is
forwarded to the server, and canceling the context will make the function return at once.
* `func (c *Connection) NewStream(ctx context.Context, h HandlerID, payload []byte) (st *Stream, err error)`
will initiate a remote call and send the initial payload.
```Go
// A Stream is a two-way stream.
// All responses *must* be read by the caller.
// If the call is canceled through the context,
//The appropriate error will be returned.
type Stream struct {
// Responses from the remote server.
// Channel will be closed after an error or when the remote closes.
// All responses *must* be read by the caller until either an error is returned or the channel is closed.
// Canceling the context will cause the context cancellation error to be returned.
Responses <-chan Response
// Requests sent to the server.
// If the handler is defined with 0 incoming capacity this will be nil.
// Channel *must* be closed to signal the end of the stream.
// If the request context is canceled, the stream will no longer process requests.
Requests chan<- []byte
}
type Response struct {
Msg []byte
Err error
}
```
There are generic versions of the server/client handlers that allow the use of type
safe implementations for data types that support msgpack marshal/unmarshal.
94 lines
2.6 KiB
Go
94 lines
2.6 KiB
Go
// Copyright (c) 2015-2023 MinIO, Inc.
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//
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// This file is part of MinIO Object Storage stack
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package grid
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import (
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"context"
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"errors"
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)
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// A Stream is a two-way stream.
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// All responses *must* be read by the caller.
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// If the call is canceled through the context,
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// the appropriate error will be returned.
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type Stream struct {
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// responses from the remote server.
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// Channel will be closed after error or when remote closes.
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// All responses *must* be read by the caller until either an error is returned or the channel is closed.
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// Canceling the context will cause the context cancellation error to be returned.
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responses <-chan Response
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cancel context.CancelCauseFunc
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// Requests sent to the server.
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// If the handler is defined with 0 incoming capacity this will be nil.
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// Channel *must* be closed to signal the end of the stream.
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// If the request context is canceled, the stream will no longer process requests.
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// Requests sent cannot be used any further by the called.
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Requests chan<- []byte
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ctx context.Context
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}
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// Send a payload to the remote server.
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func (s *Stream) Send(b []byte) error {
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if s.Requests == nil {
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return errors.New("stream does not accept requests")
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}
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select {
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case s.Requests <- b:
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return nil
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case <-s.ctx.Done():
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return context.Cause(s.ctx)
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}
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}
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// Results returns the results from the remote server one by one.
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// If any error is returned by the callback, the stream will be canceled.
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// If the context is canceled, the stream will be canceled.
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func (s *Stream) Results(next func(b []byte) error) (err error) {
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done := false
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defer func() {
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if !done {
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if s.cancel != nil {
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s.cancel(err)
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}
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// Drain channel.
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for range s.responses {
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}
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}
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}()
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for {
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select {
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case <-s.ctx.Done():
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return context.Cause(s.ctx)
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case resp, ok := <-s.responses:
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if !ok {
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done = true
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return nil
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}
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if resp.Err != nil {
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return resp.Err
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}
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err = next(resp.Msg)
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if err != nil {
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return err
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}
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}
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}
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}
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