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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.
72 lines
2 KiB
Go
72 lines
2 KiB
Go
// Copyright (c) 2015-2021 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 cmd
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import (
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"context"
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"testing"
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"github.com/minio/minio/internal/dsync"
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)
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// Tests lock rpc client.
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func TestLockRESTlient(t *testing.T) {
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// These should not be connectable.
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endpoint, err := NewEndpoint("http://localhost:9876")
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if err != nil {
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t.Fatalf("unexpected error %v", err)
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}
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endpointLocal, err := NewEndpoint("http://localhost:9012")
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if err != nil {
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t.Fatalf("unexpected error %v", err)
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}
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endpointLocal.IsLocal = true
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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err = initGlobalGrid(ctx, []PoolEndpoints{{Endpoints: Endpoints{endpoint, endpointLocal}}})
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if err != nil {
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t.Fatal(err)
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}
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lkClient := newlockRESTClient(endpoint)
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if lkClient.IsOnline() {
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t.Fatalf("unexpected result. connection was online")
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}
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// Attempt all calls.
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_, err = lkClient.RLock(context.Background(), dsync.LockArgs{})
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if err == nil {
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t.Fatal("Expected for Rlock to fail")
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}
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_, err = lkClient.Lock(context.Background(), dsync.LockArgs{})
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if err == nil {
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t.Fatal("Expected for Lock to fail")
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}
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_, err = lkClient.RUnlock(context.Background(), dsync.LockArgs{})
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if err == nil {
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t.Fatal("Expected for RUnlock to fail")
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}
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_, err = lkClient.Unlock(context.Background(), dsync.LockArgs{})
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if err == nil {
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t.Fatal("Expected for Unlock to fail")
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}
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}
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