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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.
45 lines
1.5 KiB
Go
45 lines
1.5 KiB
Go
// Code generated by "stringer -type=HandlerID -output=handlers_string.go -trimprefix=Handler msg.go handlers.go"; DO NOT EDIT.
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package grid
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import "strconv"
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func _() {
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// An "invalid array index" compiler error signifies that the constant values have changed.
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// Re-run the stringer command to generate them again.
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var x [1]struct{}
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_ = x[handlerInvalid-0]
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_ = x[HandlerLockLock-1]
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_ = x[HandlerLockRLock-2]
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_ = x[HandlerLockUnlock-3]
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_ = x[HandlerLockRUnlock-4]
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_ = x[HandlerLockRefresh-5]
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_ = x[HandlerLockForceUnlock-6]
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_ = x[HandlerWalkDir-7]
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_ = x[HandlerStatVol-8]
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_ = x[HandlerDiskInfo-9]
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_ = x[HandlerNSScanner-10]
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_ = x[HandlerReadXL-11]
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_ = x[HandlerReadVersion-12]
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_ = x[HandlerDeleteFile-13]
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_ = x[HandlerDeleteVersion-14]
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_ = x[HandlerUpdateMetadata-15]
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_ = x[HandlerWriteMetadata-16]
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_ = x[HandlerCheckParts-17]
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_ = x[HandlerRenamedata-18]
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_ = x[handlerTest-19]
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_ = x[handlerTest2-20]
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_ = x[handlerLast-21]
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}
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const _HandlerID_name = "handlerInvalidLockLockLockRLockLockUnlockLockRUnlockLockRefreshLockForceUnlockWalkDirStatVolDiskInfoNSScannerReadXLReadVersionDeleteFileDeleteVersionUpdateMetadataWriteMetadataCheckPartsRenamedatahandlerTesthandlerTest2handlerLast"
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var _HandlerID_index = [...]uint8{0, 14, 22, 31, 41, 52, 63, 78, 85, 92, 100, 109, 115, 126, 136, 149, 163, 176, 186, 196, 207, 219, 230}
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func (i HandlerID) String() string {
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if i >= HandlerID(len(_HandlerID_index)-1) {
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return "HandlerID(" + strconv.FormatInt(int64(i), 10) + ")"
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}
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return _HandlerID_name[_HandlerID_index[i]:_HandlerID_index[i+1]]
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}
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