websocket actions: Refactor registration
This commit is contained in:
Tom Wiesing
parent
08ab7b4383
commit
7b5f8a9882
4 changed files with 102 additions and 87 deletions
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@ -1,246 +0,0 @@
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package socket
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import (
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"context"
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"encoding/json"
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"errors"
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"fmt"
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"io"
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"sync"
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"time"
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"github.com/FAU-CDI/wisski-distillery/internal/dis/component"
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"github.com/FAU-CDI/wisski-distillery/internal/dis/component/auth"
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"github.com/FAU-CDI/wisski-distillery/internal/dis/component/auth/scopes"
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"github.com/gorilla/websocket"
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"github.com/tkw1536/pkglib/httpx"
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)
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// ActionMap handles a set of WebSocket actions
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type ActionMap map[string]Action
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var errReadParamsTimeout = errors.New("timeout reading the first message")
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var errUnknownAction = errors.New("unknown action call")
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var errIncorrectParams = errors.New("invalid number of parameters")
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type errPanic struct{ value any }
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func (err errPanic) Error() string {
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return fmt.Sprintf("fatal error: %v", err.value)
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}
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// Handle handles a new incoming websocket connection using the given authentication.
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//
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// There are two kinds of messages:
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//
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// - text messages, which are used to send input and output.
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// - binary messages, which are json-encoded and used for control flow.
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//
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// To call an action, a client should send a CallMessage struct.
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// The server will then start handling input and output (via text messages).
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// If the client sends a SignalMessage, the signal is propagnated to the underlying context.
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// Finally it will send a ResultMessage once handling is complete.
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//
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// A corresponding client implementation of this can be found in ..../remote/proto.ts
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func (am ActionMap) Handle(auth *auth.Auth, conn httpx.WebSocketConnection) (name string, err error) {
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var wg sync.WaitGroup
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// once we have finished executing send a binary message (indicating success) to the client.
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defer func() {
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// close the underlying connection, and then wait for everything to finish!
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defer wg.Wait()
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defer conn.Close()
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// recover from any errors
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if v := recover(); v != nil {
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err = errPanic{value: v}
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}
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// generate a result message
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var result ResultMessage
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if err == nil {
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result.Success = true
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} else {
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result.Success = false
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result.Message = err.Error()
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if result.Message == "" {
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result.Message = "unspecified error"
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}
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}
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// encode the result message to json!
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var message httpx.WebSocketMessage
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message.Type = websocket.BinaryMessage
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message.Bytes, err = json.Marshal(result)
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// silently fail if the message fails to encode
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// although this should not happen
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if err != nil {
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return
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}
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// and tell the client about it!
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<-conn.Write(message)
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}()
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// create channels to receive text and bytes messages
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textMessages := make(chan string, 10)
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binaryMessages := make(chan []byte, 10)
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// start reading text and binary messages
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// and redirect everything to the right channels
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wg.Add(1)
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go func() {
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defer wg.Done()
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defer close(textMessages)
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defer close(binaryMessages)
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for {
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select {
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case msg := <-conn.Read():
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if msg.Type == websocket.TextMessage {
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textMessages <- string(msg.Bytes)
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}
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if msg.Type == websocket.BinaryMessage {
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binaryMessages <- msg.Bytes
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}
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case <-conn.Context().Done():
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return
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}
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}
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}()
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var call CallMessage
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select {
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case buffer := <-binaryMessages:
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if err := json.Unmarshal(buffer, &call); err != nil {
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return "", errUnknownAction
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}
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case <-time.After(1 * time.Second):
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return "", errReadParamsTimeout
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}
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// check that the given action exists!
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// and has the right number of parameters!
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action, ok := am[call.Call]
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if !ok || action.Handle == nil {
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return call.Call, errUnknownAction
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}
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if action.NumParams != len(call.Params) {
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return call.Call, errIncorrectParams
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}
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// check that we have the given permission
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if err := auth.CheckScope(action.ScopeParam, action.scope(), conn.Request()); err != nil {
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return call.Call, err
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}
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// create a context to be canceled once done
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ctx, cancel := context.WithCancel(conn.Context())
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defer cancel()
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// handle any signal messages
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wg.Add(1)
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go func() {
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defer wg.Done()
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var signal SignalMessage
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for binary := range binaryMessages {
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signal.Signal = ""
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// read the signal message
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if err := json.Unmarshal(binary, &signal); err != nil {
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continue
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}
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// if we got a cancel message, do the cancellation!
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if signal.Signal == SignalCancel {
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cancel()
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}
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}
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}()
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// create a pipe to handle the input
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// and start handling it
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var inputR, inputW = io.Pipe()
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defer inputW.Close()
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wg.Add(1)
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go func() {
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defer wg.Done()
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for text := range textMessages {
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inputW.Write([]byte(text))
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}
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}()
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// write the output to the client as it comes in!
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// NOTE(twiesing): We may eventually need buffering here ...
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output := WriteFunc(func(b []byte) (int, error) {
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<-conn.WriteText(string(b))
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return len(b), nil
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})
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// handle the actual
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return call.Call, action.Handle(ctx, inputR, output, call.Params...)
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}
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// WriteFunc implements io.Writer using a function.
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type WriteFunc func([]byte) (int, error)
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func (wf WriteFunc) Write(b []byte) (int, error) {
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return wf(b)
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}
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// Action is something that can be handled via a WebSocket connection.
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type Action struct {
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// NumPara
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NumParams int
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// Scope and ScopeParam indicate the scope required by the caller.
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// TODO(twiesing): Once we actually include scopes, make them dynamic
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Scope component.Scope
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ScopeParam string
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// Handle handles this action.
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//
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// ctx is closed once the underlying connection is closed.
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// out is an io.Writer that is automatically sent to the client.
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// params holds exactly NumParams parameters.
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Handle func(ctx context.Context, in io.Reader, out io.Writer, params ...string) error
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}
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// scope returns the actual scope required by this action.
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// If the caller did not provide an actual scope, uses ScopeNever
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func (action Action) scope() component.Scope {
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if action.Scope == "" {
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return scopes.ScopeNever
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}
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return action.Scope
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}
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// CallMessage is sent by the client to the server to invoke a remote procedure
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type CallMessage struct {
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Call string `json:"call"`
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Params []string `json:"params,omitempty"`
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}
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// CancelMessage is sent from the client to the server to stop the current procedure
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type SignalMessage struct {
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Signal Signal `json:"signal"`
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}
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type Signal string
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const (
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SignalCancel = "cancel"
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)
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// ResultMessage is sent by the server to the client to report the success of a remote procedure
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type ResultMessage struct {
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Success bool `json:"success"`
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Message string `json:"message,omitempty"`
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}
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