Element Web: Message Order Issues On Bad Connections

The Frustration of Out-of-Order Messages

Element Web, a popular platform for secure and decentralized communication, aims to provide a seamless messaging experience. However, users have reported a persistent and frustrating issue: message sending order regression when on bad connectivity. This means that when your internet connection is spotty, like during a train journey through a tunnel or in a cafe with weak Wi-Fi, your messages might not only be delayed but also arrive in the wrong order. Imagine sending a crucial question, followed by a clarifying detail, only to have the detail appear before the question in the chat! This isn't just a minor glitch; it can lead to confusion, misinterpretations, and a generally poor user experience. The core of the problem seems to stem from how Element Web handles message queuing and sending operations, particularly when network requests are unreliable and prone to retries. When connectivity dips, messages can get stuck in a queue. Upon regaining a connection, the system attempts to send these queued messages, but instead of sending them one by one in the order they were composed, it appears to initiate multiple send requests concurrently. This parallelization, without proper synchronization, leads to a race condition where messages arrive at the server and subsequently appear in the timeline in an unintended sequence. This regression has been observed across various versions and is a recurring theme in user feedback, highlighting the need for a robust solution that prioritizes message order even under adverse network conditions. The developers are aware of this and are working on improvements, but understanding the user-facing impact is key to appreciating the urgency.

Diving Deeper: How Connectivity Affects Message Sending

When you're experiencing bad connectivity, your device struggles to communicate reliably with the server. In the context of Element Web, this means that when you hit 'send' on a message, the request to the server might fail, time out, or take an excessively long time to be acknowledged. The application, designed to be responsive, tries to manage this by queuing messages that haven't been successfully sent. The expectation is that once a connection is re-established or becomes stable enough, these queued messages will be sent sequentially, respecting the original order. However, the reported behavior suggests that the mechanism for unqueuing and sending these messages under poor network conditions is flawed. Instead of patiently waiting for the previous message's 'send' operation to complete successfully (indicated by a 200 OK response from the server), Element Web seems to be initiating new 'send' requests for subsequent messages in the queue, potentially before the prior ones have been confirmed. This aggressive, parallelized sending approach is the root cause of the 'out-of-order' problem. Think of it like a postman trying to deliver multiple letters at once without checking if the previous house received its mail. The result is that messages might reach the server in a jumbled sequence, and consequently, they are displayed in that same incorrect order within the chat timeline. This issue is exacerbated by the 'retry' button, which users often press when messages seem stuck, inadvertently adding more pressure to the sending mechanism and increasing the likelihood of this race condition. The fact that this has been linked to several GitHub issues over time (like #5408, #18942, and #29677) underscores its persistent nature and the complexity involved in ensuring reliable message delivery across diverse network environments. It's a challenge that requires careful management of asynchronous operations and robust error handling.

The User Experience Impact: Confusion and Frustration

This message sending order regression significantly impacts the user experience on Element Web. In real-time communication, the order of messages is fundamental to understanding the flow of a conversation. When messages are out of sequence, it creates a sense of disorientation and can lead to genuine confusion. For instance, if you're discussing plans, sending an initial suggestion followed by a modification might appear in reverse, making it difficult to follow the evolution of the idea. This is particularly problematic in professional or sensitive conversations where clarity is paramount. Users might find themselves re-reading messages, trying to piece together the correct chronological order, which defeats the purpose of instant messaging. The urgency to fix this is amplified by the platform's focus on privacy and security; users rely on Element for important communications, and such glitches can erode trust. The repeated nature of this bug, as indicated by its presence in multiple GitHub issues dating back several years, suggests that it's not a simple fix and requires a fundamental re-evaluation of how the client handles network instability and message queuing. The development team's acknowledgment and efforts to address this are crucial, as a reliable and predictable messaging experience is at the heart of any communication tool. When the core functionality of sending and receiving messages in the correct order falters, especially under common conditions like fluctuating network quality, it detracts from the overall utility and polish of the application. It's the kind of issue that can lead users to seek alternatives, even if they appreciate other aspects of the platform.

Technical Deep Dive: Parallel Sends and Race Conditions

Let's get a bit more technical about the Element Web message sending regression. The issue arises from how the client attempts to send messages when the network is unstable. When a message fails to send, the client typically queues it for a retry. However, under poor connectivity, multiple messages might end up in this queue. The problem occurs during the unqueuing process. Instead of a strict, sequential sending approach—where the client waits for a confirmation (a 200 OK response from the server's /send endpoint) for the first message before attempting to send the second—the client seems to be initiating parallel /send requests. This parallelization can happen if the internal logic doesn't properly await the completion of each asynchronous send operation. Consequently, if multiple send operations are initiated in quick succession, and the network latency is high or packets are being dropped, these requests can arrive at the homeserver in an arbitrary order. The server processes these requests as they arrive, leading to the messages appearing in the chat timeline out of their original composition order. This is a classic example of a race condition in concurrent programming. To prevent this, the client needs a more robust state management system for outgoing messages. This could involve implementing a strict queue where each message's send operation must fully complete (either success or a definitive failure with a clear error code) before the next message in the queue is processed. Furthermore, the handling of retries needs to be carefully managed to avoid overwhelming the network or creating further race conditions. The existing links to GitHub issues suggest that this problem has been tackled before, possibly with partial fixes that didn't fully resolve the underlying architectural issue, or perhaps the problem re-emerged with subsequent code changes. The version information provided (Element version: 4987d6c57371-js-942fdf5bee0f, Rust SDK 0.14.0, Vodozemac 0.9.0) indicates the specific software stack where this is being observed, and the use of develop.element.io points to a testing or development environment, which is valuable for debugging.

Reproducing the Issue: A Step-by-Step Scenario

Reproducing the message sending order regression in Element Web requires specific conditions, primarily a degraded network connection. The steps provided by the user offer a clear path to observe this behavior: 1. Be on bad connectivity (Eurostar in this case). This is the crucial first step. Any scenario that introduces high latency, packet loss, or intermittent connection drops will suffice. Examples include being in a tunnel, on a train, in a crowded public space with poor Wi-Fi, or even simulating these conditions using network throttling tools. 2. Queue up some messages. Once on a bad connection, type out and prepare several messages without sending them immediately. This creates the backlog that will be susceptible to ordering issues. 3. Probably stab 'retry' a few times. When messages show as unsent (often indicated by a clock icon or similar status), users will naturally try to resend them. Repeatedly hitting the 'retry' button, especially when the connection is still unstable, can trigger the flawed sending logic. 4. When they finally unqueue, they send in the wrong order. As the network connection improves slightly or the system attempts to push the queued messages, they are sent out. Due to the parallelization issue discussed, they don't necessarily go out in the order they were composed or queued. 5. Interestingly(?) they are then shown in the wrong order in the timeline. The final observable symptom is that these out-of-order sent messages appear jumbled in the chat history, confirming the regression. The user's expectation is that the client should intelligently manage these queued messages, sending them serially and ensuring that the /send operation for message B only commences after the /send operation for message A has successfully completed (returned a 200 OK). What happens instead is that multiple /send calls are initiated concurrently, leading to the race condition and the incorrect ordering observed in the timeline. This methodical approach to reproduction is vital for developers to pinpoint the exact lines of code responsible for this behavior and implement effective fixes.

Conclusion and Looking Forward

The message sending order regression on bad connectivity is a significant usability issue for Element Web. It undermines the reliability users expect from a communication platform and can lead to confusion and miscommunication. The technical cause, rooted in how the client handles asynchronous message sending and retries under unstable network conditions, is well-understood as a race condition arising from parallelized send operations. While the development team is aware of this and has linked it to existing issues, the persistence of the bug highlights the complexity of ensuring robust network handling in a real-world, unpredictable environment. The provided details, including the specific application and browser versions, along with the homeserver information, are invaluable for debugging efforts. Moving forward, the focus must be on implementing a more robust queuing and sequential sending mechanism within Element Web. This involves ensuring that each message send operation is fully acknowledged before the next one is initiated, especially during periods of poor connectivity. Implementing better error handling and retry strategies that do not contribute to race conditions will also be critical. Community feedback and bug reports like this are essential for driving improvements. For those interested in the technical underpinnings of secure messaging and decentralized communication protocols, exploring resources like the Matrix.org website can provide deeper insights into the architecture and ongoing development of these technologies. Additionally, the Element Help Center offers valuable information and support for users encountering various issues.