EventCatalog Visualizer: Fixing Duplicate Channel Labels

Hey there, fellow event-driven architecture enthusiasts! Today, we're diving deep into a common head-scratcher that many of us encounter when working with EventCatalog v2: the perplexing issue of duplicate channel labels appearing in the visualizer. It's a scenario that can quickly turn a beautifully crafted event catalog into a cluttered mess, making it harder to grasp the intricate relationships between your services and events. We've all been there, staring at a diagram where a single channel connection is repeated multiple times, each adorned with identical labels like "subscribed by & subscribed by & subscribed by." This can happen even when your Channel MDX files are pristine, containing no explicit relationships, and you're solely relying on the sends or receives tags within your service MDX files. This might sound like a minor glitch, but in the complex world of event-driven systems, clarity is king. When your visualizer starts duplicating these connections and labels, it not only clutters the visual representation but also introduces ambiguity. Is this connection truly happening multiple times, or is it just a display artifact? This confusion can lead to misunderstandings, misinterpretations of your event flow, and ultimately, a less effective and harder-to-maintain event catalog. The goal of EventCatalog is to provide a clear, concise, and easily navigable map of your event landscape, and these duplicates directly undermine that objective. This article aims to dissect this issue, understand why it occurs, and most importantly, walk you through how to achieve the expected, clean, and deduplicated labels in your EventCatalog v2 visualizer, ensuring your diagrams are as informative as they are aesthetically pleasing. We'll explore the nuances of how EventCatalog interprets relationships and how to guide it towards a more streamlined visualization.

Understanding the Duplicate Label Dilemma in EventCatalog Visualizer

Let's get to the heart of the matter: why does EventCatalog v2 sometimes insist on showing us multiple instances of the same connection and label in the visualizer? This phenomenon typically arises when a single service is configured to interact with the same event channel through multiple distinct event definitions. Imagine a scenario where your OrderService not only receives an OrderCreated event but also receives an OrderUpdated event, both originating from the same OrderChannel. In the EventCatalog v2 architecture, each of these interactions, even if they share the same source channel, is treated as a separate relationship. The visualizer's job is to depict all the defined relationships. When it encounters these multiple receives directives pointing to the same channel from the same service, it dutifully draws a separate line for each. The label concatenation, like "subscribed by & subscribed by," is EventCatalog's way of indicating that the service is subscribed to this channel, and it's trying to represent the cumulative nature of these subscriptions. However, as we've noted, this leads to redundancy. The core issue isn't necessarily a bug, but rather how the visualizer interprets and displays multiple, identical relationship types originating from the same source and pointing to the same destination. The system is designed to be explicit, and if you define multiple ways a service interacts with a channel, it will visualize each one. The expected behavior, of course, is a more intelligent deduplication. We want to see a single line representing the service's subscription to the channel, with a clear label that signifies this connection, rather than a cluttered series of identical annotations. This is crucial for maintaining the integrity and readability of your event architecture diagrams. The problem statement highlights that this occurs even when the channel MDX has no explicit relationships defined, and only service MDX uses sends or receives. This implies that the interpretation of these relationship directives within the service MDX is the primary driver for the duplicate edges and labels. It's a subtle but important distinction that affects how we approach the solution. We need to find a way to consolidate these multiple, implicit relationships into a single, clear representation within the visualizer.

Achieving Clean Deduplicated Labels: Practical Solutions

Now that we understand the root cause – multiple relationship definitions leading to duplicate visual elements – let's talk solutions. The good news is that EventCatalog v2 offers ways to manage this and achieve the clean, deduplicated labels you expect. The most straightforward approach involves being more deliberate with your receives and sends directives within your service MDX files. Instead of defining separate receives for each event from the same channel, you can often consolidate them. For instance, if a service receives OrderCreated and OrderUpdated from OrderChannel, you might structure your MDX like this: receives: OrderChannel(OrderCreated, OrderUpdated). This tells EventCatalog that the service receives multiple events from the same channel, and it should ideally be interpreted as a single subscription to that channel, thus resulting in a single visual edge and a consolidated label. This approach leverages EventCatalog's ability to handle multiple events within a single channel definition. If your receives or sends directives are spread across different lines or sections within your MDX, consider refactoring them to group related events from the same channel. Another strategy, particularly if you're encountering this with different types of relationships (though the problem statement focuses on identical ones), is to ensure your relationship definitions are as specific as possible. However, for the exact issue of duplicate identical labels, the consolidation within a single receives or sends directive is the most potent solution. Sometimes, the issue might also stem from how EventCatalog is processing the relationships internally. In versions prior to v2.65.1, there might have been less sophisticated deduplication logic. Therefore, ensuring you are on the latest stable version of @eventcatalog/core and @eventcatalog/sdk is paramount. We're using v2.65.1 and v2.9.5 in the example, which should generally have improved handling. If consolidation within the MDX doesn't yield the desired result, you might need to look into custom relationship definitions or potentially explore the EventCatalog configuration options for visualizer behavior, although EventCatalog is generally opinionated about its visualizer. The key is to guide EventCatalog to understand that multiple implicit relationships to the same channel should be represented as a single logical connection. By grouping events within a single channel directive in your service MDX, you're providing that clearer signal, allowing the visualizer to consolidate the information effectively and present a much cleaner, more informative diagram.

Advanced Strategies and Future Considerations

While consolidating your receives and sends directives within service MDX is the primary and most effective way to tackle duplicate channel labels in the EventCatalog v2 visualizer, let's explore some advanced strategies and future considerations. Occasionally, the structure of your event definitions or the way relationships are implicitly formed might still lead to unexpected duplicates, even after applying the consolidation techniques. In such cases, delving into EventCatalog's configuration and potentially custom components might be necessary. Although EventCatalog v2 aims for a declarative approach, understanding its underlying graph generation process can be insightful. The visualizer constructs a graph where nodes represent services and events, and edges represent relationships. When multiple edges are created between the same two nodes with the same relationship type, the default behavior is to display them. The goal is to influence this graph generation to only create a single edge. If direct MDX consolidation doesn't fully resolve the issue, exploring options within the .eventcatalog/config.js file might reveal settings related to visualizer rendering or relationship aggregation. However, it's important to note that EventCatalog's configuration options for the visualizer are somewhat limited by design, prioritizing simplicity and convention. A more advanced, albeit more involved, approach could involve preprocessing your event definitions or developing custom plugins for EventCatalog. This would allow you to programmatically identify and merge redundant relationship definitions before they are processed by the visualizer. This level of customization is typically reserved for complex scenarios or when the standard declarative approach doesn't meet specific organizational needs. Looking ahead, it's always beneficial to stay updated with the latest releases of EventCatalog. The development team is continually refining the tool, and future versions might include more robust automatic deduplication logic or enhanced configuration options for the visualizer. Keeping an eye on the official EventCatalog GitHub repository and its release notes can provide valuable insights into upcoming features and bug fixes. Furthermore, contributing to the EventCatalog community by reporting issues and suggesting enhancements can help shape the tool's evolution. Remember, the aim is always to foster a clear and accurate representation of your event-driven architecture. While the immediate solution lies in refining your MDX, understanding these advanced strategies and keeping an eye on the project's development ensures you're equipped to handle even the most intricate visualization challenges. The power of a good event catalog lies in its clarity, and these techniques help maintain that clarity.

Conclusion: Streamlining Your Event Catalog Visualizations

In summary, the issue of duplicate channel labels in the EventCatalog v2 visualizer, while initially frustrating, is fundamentally a reflection of how multiple relationship definitions are interpreted. When a service interacts with the same channel multiple times, EventCatalog, by default, visualizes each interaction separately, leading to redundant edges and concatenated labels like "subscribed by & subscribed by." The most effective and recommended solution is to consolidate your receives and sends directives within your service MDX files. By grouping all events from a specific channel under a single directive, you signal to EventCatalog that these are part of a unified relationship, prompting it to render a single, clean visual edge with a unified label. This approach not only resolves the clutter but also makes your event catalog significantly more readable and maintainable. Always ensure you are using the latest stable versions of @eventcatalog/core and @eventcatalog/sdk as improvements in handling and deduplication are continuously being made. For more complex scenarios or if standard consolidation doesn't suffice, exploring advanced strategies like custom processing or keeping abreast of future EventCatalog releases becomes crucial. Ultimately, a well-organized and clearly visualized event catalog is an invaluable asset for understanding and managing your event-driven architecture. By implementing these best practices, you can ensure your EventCatalog visualizer remains a powerful tool for clarity, not a source of confusion.

For further insights into event-driven architecture best practices and advanced tooling, you can explore resources from Cloud Native Computing Foundation (CNCF).