Invoker Middlewares

MTGo provides an invoker middleware system that intercepts outgoing RPC calls to Telegram. Unlike handler middleware (which wraps update processing), invoker middleware wraps the actual RPC invocation — perfect for rate limiting, flood wait handling, logging, and retries.

InvokerMiddleware Type

type InvokerMiddleware func(next tg.Invoker) tg.Invoker

Where tg.Invoker is:

type Invoker interface {
    RPCInvoke(ctx context.Context, input tg.TLObject, decode func(io.Reader) (tg.TLObject, error)) (tg.TLObject, error)
}

Registering Middleware

client.UseInvokerMiddleware(myMiddleware)

Multiple middleware are composed in registration order: the first registered wraps all subsequent ones.

Official Middlewares

Middleware	Description
Flood Wait	Auto-handles FLOOD_WAIT errors with sleep and retry
Rate Limit	Token-bucket rate limiter for outgoing RPC calls

Composing Middleware

Register multiple middleware to build a processing pipeline:

// Rate limit runs first (outermost), then flood wait handles any bursts that get through
limiter := ratelimit.New(30, 10)
waiter := floodwait.New()

client.UseInvokerMiddleware(limiter.Middleware())
client.UseInvokerMiddleware(waiter.Middleware())

Custom Invoker Middleware

Use the middleware template to create custom invoker middleware:

package mymiddleware

import (
    "context"
    "io"
    "log"
    "time"

    "github.com/mtgo-labs/mtgo/tg"
)

func Middleware() func(next tg.Invoker) tg.Invoker {
    return func(next tg.Invoker) tg.Invoker {
        return tg.InvokerFunc(func(ctx context.Context, input tg.TLObject, decode func(io.Reader) (tg.TLObject, error)) (tg.TLObject, error) {
            start := time.Now()
            log.Printf("RPC: %T", input)

            result, err := next.RPCInvoke(ctx, input, decode)

            log.Printf("RPC: %T done in %v (err=%v)", input, time.Since(start), err)
            return result, err
        })
    }
}

Usage:

client.UseInvokerMiddleware(mymiddleware.Middleware())

Handler Middleware vs Invoker Middleware

Feature	Handler Middleware	Invoker Middleware
Scope	Incoming updates	Outgoing RPC calls
Registration	client.UseMiddleware(mw)	client.UseInvokerMiddleware(mw)
Use cases	Auth, logging, i18n	Rate limiting, flood wait, retries
Priority	Supports priority parameter	Registration order

Middleware Template

The middlewares-template repository provides a starting point:

cp -r middlewares-template/ middlewares/my-middleware

See Middleware Template for the full guide.