Message delivery issues in EFB Telegram Master channel (comparing to generic IM services)

Different from how usually an IM would work, EFB Telegram Master channel (ETM) strongly rely on Telegram Bot platform. This had made ETM more difficult to deal with messages failed to deliver.

This article is first published on ETM Wiki on 20 April, 2019.

Dealing errors in a generic IM (example)

Below is a simplified flow of message delivery in a generic IM.

ETM-0 — A simplified flow of message delivery in a generic IM

PlantUML Syntax:<br />
@startuml<br />
skinparam monochrome reverse<br />
skinparam sequenceReferenceAlign center<br />
skinparam sequenceMessageAlign center</p>
<p>actor User</p>
<p>== Send message ==</p>
<p>User -> Client: 1.1. Send message<br />
activate Client<br />
Client -> Server: 1.1.1. Deliver message<br />
activate Server<br />
Server -> Server: 1.1.2. Verify message content<br />
activate Server<br />
deactivate Server<br />
Server -> : 1.1.3 Send to recipient<br />
Server –> Client: 1.1.4. Delivery receipt<br />
deactivate Server<br />
deactivate Client</p>
<p>== Receive message ==</p>
<p>Server <- : 1.2. Receive new message
activate Server
Server -> Client: 1.2.1 Notify client<br />
activate Client<br />
Client -> Server: 1.2.2. Retrieve message<br />
activate Server<br />
Client <-- Server: message
deactivate Server
deactivate Server
Client -> User: 1.2.3 Notify user<br />
deactivate Client<br />
@enduml<br />
” usemap=”#plantuml_map”></p>

<p>Error could occur in one or more of the following scenarios:</p>

<h3 class=

1.1.1. Deliver message If the client failed to send a message to the server, it would keep the message locally and retry when possible, until a receipt is received from the server.In the case where the server received the message but the receipt is failed to deliver back, the client would continue to try sending the message to server. But since the server keeps a record of all messages with their ID, it could simply identify the request as duplicate, drop it, and redeliver the receipt. 1.1.2. Verify message contentMalformed message content can be detected, and rejected by the server, which can be reflected on the receipt. The client can know that the message is rejected and prompt user to try resend. 1.2.1. Notify clientSimilar to 1.1.1., a receipt-based mechanism can be implemented to notifications as well. Even if the notification is delivered without receipt, and missed, the user may still open the app and see the message when message queues are refreshed. 1.2.2. Retrieve messageThis is always a stable step. Similar to an HTTP GET request, it can always retry the request until getting what it wants. Parameters like “last message ID” can be used to minimize the data of content during retries. Dealing errors in ETMBelow is a simplified workflow of ETM message delivery.

Message delivery issues in EFB Telegram Master channel (comparing to generic IM services)

Dealing errors in a generic IM (example)

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