How to Handle Long Polling Offset Management in Telego

Telego automatically manages the offset parameter for Telegram's getUpdates method by incrementing the internal counter to UpdateID + 1 after processing each batch, ensuring no duplicate updates are received.

The offset parameter is critical for long-polling in the Telegram Bot API, telling the server which updates you've already processed. In Telego, the Go library for Telegram bots, this offset management is handled automatically within the UpdatesViaLongPolling method, though developers can override this behavior when persisting state across restarts.

How Telego Manages the Offset Automatically

Telego's long-polling implementation tracks the offset parameter internally so you don't have to calculate it manually. The core logic lives in long_polling.go within the UpdatesViaLongPolling and doLongPolling functions.

The UpdatesViaLongPolling Entry Point

When you initiate long polling, UpdatesViaLongPolling creates a copy of your GetUpdatesParams (or uses defaults if you pass nil) and launches doLongPolling in a separate goroutine. This design ensures that the offset state is maintained throughout the bot's lifecycle.

// From long_polling.go lines 68-78
updates := &UpdatesViaLongPolling{
    bot:    b,
    params: *params, // Copy of params with offset
    // ... other fields
}
go updates.doLongPolling(ctx)

The Internal doLongPolling Loop

Inside doLongPolling, every batch returned by Bot.GetUpdates is processed sequentially. For each update whose UpdateID is greater than or equal to the current params.Offset, the offset is advanced to UpdateID + 1. This increment happens immediately after the update is received, ensuring that Telegram never sends that update again.

// From long_polling.go lines 38-40
if upd.UpdateID >= params.Offset {
    params.Offset = upd.UpdateID + 1
}

This mechanism works because Telegram's getUpdates method only returns updates with an update_id strictly greater than the supplied offset parameter. By setting params.Offset to the last processed ID plus one, Telego guarantees exactly-once delivery semantics for your bot handlers.

When to Manually Control the Offset

While automatic offset management handles most use cases, there are scenarios where you need to intervene:

• Standard usage: Simply call UpdatesViaLongPolling with params set to nil or only specify Timeout. Telego updates the offset internally; you do not need to manage it.
• Persisting progress: When restarting your bot, you want to avoid re-processing old updates. Store the latest offset (e.g., in a file or database) after each update and supply it on the next start via GetUpdatesParams{Offset: savedOffset}.
• Skipping updates: If you need to ignore a specific range of historical updates, initialize params.Offset with the desired starting ID before calling UpdatesViaLongPolling. The internal loop will continue from that point.

Configuration Options for Long Polling

Telego provides several functional options to customize the polling behavior in long_polling.go:

• WithLongPollingUpdateInterval – Adds a pause between successive GetUpdates calls, useful for respecting rate limits or reducing server load.
• WithLongPollingRetryTimeout – Sets the wait time before retrying after a network or API error.
• WithLongPollingBuffer – Defines the size of the buffered channel that receives updates, controlling backpressure.

Practical Code Examples

Basic Long Polling with Automatic Offset

For most bots, simply start the long poller and let Telego handle the offset:

ctx := context.Background()
bot, err := telego.NewBot("YOUR_BOT_TOKEN", telego.WithDefaultDebugLogger())
if err != nil {
    log.Fatal(err)
}

updates, err := bot.UpdatesViaLongPolling(ctx, nil) // nil uses defaults & auto offset
if err != nil {
    log.Fatal(err)
}

for update := range updates {
    fmt.Printf("Processing update %d from chat %d\n", 
        update.UpdateID, update.Message.Chat.ID)
}

Telego automatically increments the offset after each update, ensuring you never receive duplicates.

Persisting Offset Between Restarts

To avoid processing the same updates after a bot restart, persist the offset to storage:

// Helper functions to implement based on your storage (file, Redis, etc.)
func loadOffsetFromFile() int64 { /* ... */ return 0 }
func saveOffsetToFile(offset int64) { /* ... */ }

func main() {
    ctx := context.Background()
    bot, _ := telego.NewBot("TOKEN")
    
    // Load previous state
    savedOffset := loadOffsetFromFile()
    
    params := &telego.GetUpdatesParams{
        Offset:  savedOffset,
        Timeout: 8,
    }
    
    updates, _ := bot.UpdatesViaLongPolling(ctx, params)
    
    for upd := range updates {
        handleUpdate(upd)
        
        // Persist next expected offset (current ID + 1)
        saveOffsetToFile(upd.UpdateID + 1)
    }
}

This pattern ensures that even if the bot crashes, it resumes from the correct position without missing or duplicating messages.

Custom Polling Intervals and Error Handling

Control the polling behavior to respect rate limits or handle network instability:

updates, err := bot.UpdatesViaLongPolling(
    ctx,
    &telego.GetUpdatesParams{Timeout: 10},
    telego.WithLongPollingUpdateInterval(2*time.Second), // 2s pause between polls
    telego.WithLongPollingRetryTimeout(5*time.Second),   // 5s wait after errors
    telego.WithLongPollingBuffer(100),                   // Buffer 100 updates
)
if err != nil {
    log.Fatal(err)
}

These options help prevent hitting Telegram API limits and provide resilience against temporary network failures.

Key Source Files and Implementation Details

Understanding the source structure helps when debugging or extending Telego's behavior:

File	Purpose	Link
long_polling.go	Core long-polling logic, offset handling, and configuration options	Source
methods.go	Defines GetUpdatesParams struct including the Offset field	Source
examples/updates_long_polling/main.go	Working example demonstrating automatic offset management	Source
bot.go	Contains runner management to prevent concurrent polling/webhook conflicts	Source

The offset logic specifically resides in the doLongPolling method within long_polling.go, where the comparison if upd.UpdateID >= params.Offset ensures that only new updates advance the counter.

Summary

• Telego handles offsets automatically through the UpdatesViaLongPolling method, incrementing the internal counter to UpdateID + 1 after each processed update.
• Manual intervention is only needed when persisting state across restarts or when intentionally skipping historical updates.
• Key implementation resides in long_polling.go, specifically within the doLongPolling loop that checks upd.UpdateID >= params.Offset.
• Configuration options like WithLongPollingUpdateInterval and WithLongPollingRetryTimeout provide control over polling frequency and error resilience.
• Persistence pattern involves storing update.UpdateID + 1 after each message and supplying it as GetUpdatesParams.Offset on the next startup.

Frequently Asked Questions

Does Telego require manual offset management?

No. By default, Telego automatically manages the offset parameter when you use UpdatesViaLongPolling. The library maintains an internal counter in long_polling.go that advances to UpdateID + 1 after each update is received, ensuring Telegram never sends duplicates. You only need to manually specify an offset when persisting state across bot restarts or when intentionally skipping historical messages.

How do I persist the offset across bot restarts?

To avoid re-processing updates after a restart, store the latest offset value after each update and supply it when initializing the bot. Implement a storage mechanism (file, database, or cache) to save update.UpdateID + 1 after processing each message. On startup, load this value and pass it as GetUpdatesParams.Offset. According to the implementation in long_polling.go, Telego will resume from this position and continue automatic management from there.

What happens if I provide a custom offset?

When you initialize UpdatesViaLongPolling with a GetUpdatesParams struct containing a specific Offset value, Telego starts polling from that update ID. The internal doLongPolling loop in long_polling.go compares each incoming update's UpdateID against your provided offset, only processing updates where UpdateID >= params.Offset. After processing begins, Telego automatically increments the offset internally, so your manual setting only affects the starting position.

How does Telego prevent duplicate updates?

Telego implements an exact-once delivery guarantee for updates within a single polling session by strictly adhering to Telegram's offset semantics. In long_polling.go, the doLongPolling method checks each update against the current params.Offset and immediately advances the offset to UpdateID + 1 before the update is dispatched to your handler channel. Since Telegram's getUpdates method only returns updates with IDs strictly greater than the provided offset, this incremental approach ensures that once an update ID is acknowledged, it will never be fetched again, even if the bot restarts (provided you persist the offset).

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}