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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.
114 lines
3.4 KiB
Go
114 lines
3.4 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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"errors"
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"github.com/minio/minio/internal/dsync"
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"github.com/minio/minio/internal/grid"
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"github.com/minio/minio/internal/logger"
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)
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// lockRESTClient is authenticable lock REST client
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type lockRESTClient struct {
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connection *grid.Connection
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}
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// IsOnline - returns whether REST client failed to connect or not.
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func (c *lockRESTClient) IsOnline() bool {
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return c.connection.State() == grid.StateConnected
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}
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// Not a local locker
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func (c *lockRESTClient) IsLocal() bool {
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return false
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}
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// Close - marks the client as closed.
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func (c *lockRESTClient) Close() error {
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return nil
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}
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// String - returns the remote host of the connection.
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func (c *lockRESTClient) String() string {
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return c.connection.Remote
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}
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func (c *lockRESTClient) call(ctx context.Context, h *grid.SingleHandler[*dsync.LockArgs, *dsync.LockResp], args *dsync.LockArgs) (ok bool, err error) {
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r, err := h.Call(ctx, c.connection, args)
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if err != nil {
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logger.LogIfNot(ctx, err, grid.ErrDisconnected)
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return false, err
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}
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defer h.PutResponse(r)
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ok = r.Code == dsync.RespOK
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switch r.Code {
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case dsync.RespLockConflict, dsync.RespLockNotFound, dsync.RespOK:
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// no error
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case dsync.RespLockNotInitialized:
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err = errLockNotInitialized
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default:
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err = errors.New(r.Err)
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}
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return ok, err
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}
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// RLock calls read lock REST API.
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func (c *lockRESTClient) RLock(ctx context.Context, args dsync.LockArgs) (reply bool, err error) {
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return c.call(ctx, lockRPCRLock, &args)
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}
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// Lock calls lock REST API.
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func (c *lockRESTClient) Lock(ctx context.Context, args dsync.LockArgs) (reply bool, err error) {
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return c.call(ctx, lockRPCLock, &args)
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}
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// RUnlock calls read unlock REST API.
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func (c *lockRESTClient) RUnlock(ctx context.Context, args dsync.LockArgs) (reply bool, err error) {
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return c.call(ctx, lockRPCRUnlock, &args)
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}
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// Refresh calls Refresh REST API.
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func (c *lockRESTClient) Refresh(ctx context.Context, args dsync.LockArgs) (reply bool, err error) {
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return c.call(ctx, lockRPCRefresh, &args)
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}
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// Unlock calls write unlock RPC.
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func (c *lockRESTClient) Unlock(ctx context.Context, args dsync.LockArgs) (reply bool, err error) {
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return c.call(ctx, lockRPCUnlock, &args)
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}
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// ForceUnlock calls force unlock handler to forcibly unlock an active lock.
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func (c *lockRESTClient) ForceUnlock(ctx context.Context, args dsync.LockArgs) (reply bool, err error) {
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return c.call(ctx, lockRPCForceUnlock, &args)
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}
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func newLockAPI(endpoint Endpoint) dsync.NetLocker {
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if endpoint.IsLocal {
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return globalLockServer
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}
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return newlockRESTClient(endpoint)
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}
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// Returns a lock rest client.
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func newlockRESTClient(ep Endpoint) *lockRESTClient {
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return &lockRESTClient{globalGrid.Load().Connection(ep.GridHost())}
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}
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