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118 lines
3.1 KiB
Go
118 lines
3.1 KiB
Go
// Package wsutil provides abstractions around the Websocket, including rate
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// limits.
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package ws
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import (
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"context"
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"fmt"
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"log"
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"sync"
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"golang.org/x/time/rate"
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)
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var (
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// WSError is the default error handler
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WSError = func(err error) { log.Println("Gateway error:", err) }
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// WSDebug is used for extra debug logging. This is expected to behave
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// similarly to log.Println().
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WSDebug = func(v ...interface{}) {}
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)
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// Websocket is a wrapper around a websocket Conn with thread safety and rate
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// limiting for sending and throttling.
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type Websocket struct {
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mutex sync.Mutex
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conn Connection
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addr string
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// If you ever need access to these fields from outside the package, please
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// open an issue. It might be worth it to refactor these out for distributed
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// sharding.
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sendLimiter *rate.Limiter
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dialLimiter *rate.Limiter
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}
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// NewWebsocket creates a default Websocket with the given address.
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func NewWebsocket(c Codec, addr string) *Websocket {
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return NewCustomWebsocket(NewConn(c), addr)
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}
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// NewCustomWebsocket creates a new undialed Websocket.
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func NewCustomWebsocket(conn Connection, addr string) *Websocket {
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return &Websocket{
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conn: conn,
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addr: addr,
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sendLimiter: NewSendLimiter(),
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dialLimiter: NewDialLimiter(),
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}
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}
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// Dial waits until the rate limiter allows then dials the websocket.
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func (ws *Websocket) Dial(ctx context.Context) (<-chan Op, error) {
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if err := ws.dialLimiter.Wait(ctx); err != nil {
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// Expired, fatal error
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return nil, fmt.Errorf("failed to wait for dial rate limiter: %w", err)
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}
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ws.mutex.Lock()
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defer ws.mutex.Unlock()
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// Reset the send limiter.
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// TODO: see if each limit only applies to one connection or not.
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ws.sendLimiter = NewSendLimiter()
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return ws.conn.Dial(ctx, ws.addr)
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}
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// Send sends b over the Websocket with a deadline. It closes the internal
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// Websocket if the Send method errors out.
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func (ws *Websocket) Send(ctx context.Context, b []byte) error {
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WSDebug("Acquiring the websocket mutex for sending.")
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ws.mutex.Lock()
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sendLimiter := ws.sendLimiter
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conn := ws.conn
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ws.mutex.Unlock()
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WSDebug("Waiting for the send rate limiter...")
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if err := sendLimiter.Wait(ctx); err != nil {
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WSDebug("Send rate limiter timed out.")
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return fmt.Errorf("SendLimiter failed: %w", err)
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}
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WSDebug("Send has passed the rate limiting.")
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return conn.Send(ctx, b)
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}
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// Close closes the websocket connection. It assumes that the Websocket is
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// closed even when it returns an error. If the Websocket was already closed
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// before, ErrWebsocketClosed will be returned.
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func (ws *Websocket) Close() error {
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WSDebug("Conn: Acquiring mutex lock to close...")
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ws.mutex.Lock()
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defer ws.mutex.Unlock()
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WSDebug("Conn: Write mutex acquired")
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return ws.conn.Close(false)
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}
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// CloseGracefully is similar to Close, but a proper close frame is sent to
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// Discord, invalidating the internal session ID and voiding resumes.
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func (ws *Websocket) CloseGracefully() error {
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WSDebug("Conn: Acquiring mutex lock to close...")
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ws.mutex.Lock()
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defer ws.mutex.Unlock()
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WSDebug("Conn: Write mutex acquired")
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return ws.conn.Close(true)
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}
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