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Hello everyone! Hello Thailand! I want to thank you for having me here.
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It's my second time in Thailand and my first time in Bangkok. Yesterday, we tried to install Party Jam.
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I found it, but I'm not sure if I really want to install it. So, this is not my first trip to Asia.
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This is why I really know what jet lag is. It’s tough because I have no idea whether to wake up at 4 a.m. or go to sleep at 3 p.m.
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Yesterday, I was inspired by a team I really love. I tried to find something interesting on the Internet.
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Unfortunately, I found nothing useful. I thought perhaps looking for 'Quest of Rubies' would be super complicated on Google, and I tried to find Ruby Nia but wasn't sure if it would be helpful.
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So, okay, my name is Anton. I am from Moscow. You can find my contact information if needed.
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I'm a top talent architect, and I can use this opportunity to share some insights. It's my favorite topic involving architecture.
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Some people know me as the guy who works on Crimea and strong systems. I really love open source. Right now, I’m a core developer.
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However, I know the theater world as well. Sometimes, I stream on Twitch. You might want to know that I really love stickers.
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I have a collection of stickers, and I also love burritos. I even have a photo of myself in Minsk enjoying a burrito. I love that photo because I look like a person who could be on a Japanese TV show.
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If you want to talk with me, we can discuss coffee, beer, or psychology. I have a Nintendo Switch, and I really love to draw images for our presentations.
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The first drawing was done by me, and I also enjoy writing good stories.
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I expected to be like a certain type of storyteller, but unfortunately, reality turned out to be a bit different.
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However, I consider myself lucky because I got help from my friend Georgie. He is really quiet and sometimes asks insightful questions.
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Today, the title of my talk is 'Events.' We will discuss these in general. In the real world, we encounter numerous events.
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As developers, we often need to capture these events and take action. For example, does anyone know what a commit is?
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Indeed, we can say that each commit represents something that happened. For instance, I have a dynamic contributions application, and we keep a list of commits.
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Each commit contains a description of changes, metadata, and information about what happened.
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If we open a commit from a repository, we see that it includes a description of changes, the associated files, and metadata about who made changes and when.
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Another example of events is what happens when a user tries to purchase an item in an online shop application.
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We need to track exactly what the user added to their order and what was deleted from it.
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We have to sometimes work with deleted activity. My favorite topic is tracking deleted data in the database.
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Unfortunately, in our applications, we mostly deal with the current state, meaning we focus only on what is happening at this moment.
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In this case, we say our events reflect our actions, and the current state is our data in the database.
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This leads us to the point that we often look at current data rather than considering how to store event histories.
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So, you might be asking, what would happen if we changed our approach to start storing events instead of focusing only on the current data?
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In this case, we would enter the realm of event sourcing. Today’s discussion covers both event sourcing and its significance.
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The first rule of event sourcing is that nobody knows what event sourcing is. The second rule is that you must store what happened with the application.
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This involves capturing events rather than simply storing the current state.
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The first question you should ask yourself is where to store these events. You can keep a list of events or a chain of events.
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In event sourcing, event storage can take various forms—it can be Redis, Kafka, MongoDB, or SQL databases.
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Event storage has certain rules: the first is that an event must have occurred in the past.
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We may not know how long ago it took place, but it’s important to remember that it happened.
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The next rule is that events should be immutable. We cannot update, modify, or delete events once they occur.
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Instead, we can only create new events to adjust for changes or updates.
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Let’s consider a simple example of event storage: when a user is created, we log that event. Later, if we want to update the user's information, we don’t change the initial event but create a new one.
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The next challenge in event storage is ensuring that we have valid data in each event.
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This means validating data against our database before we store an event.
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The second rule of event sourcing is data evolution. This implies that events must adapt over time without altering the history.
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Documentation must remain unchanged while allowing increased complexity in the application.
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Data evolution requires us to accommodate different event schemas concurrently.
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It's crucial to remember that the application could experience significant changes over time.
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Now, let’s move on to how we can derive the current state from an event store.
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In event sourcing, we use projections to calculate specific states from the event history.
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Projections act as functions that take the list of events and an initial state, then compute a specific state.
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In this context, the projection function is inherently a pure function, and its behavior is predictable.
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To illustrate, after a user is created, we can accumulate events and check if the user has been updated.
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The concern, however, is that recalculating the current state every time can slow down performance.
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Especially when events can span 2 or 10 years, handling accumulation can become a hefty task.
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In Ruby or other languages, performance issues may arise, but there are ways to resolve this.
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We could introduce abstraction with colored streams to better manage smaller sets of events.
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For instance, with two different event sources, we could create specific streams for individual sources.
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This would allow us to only process relevant events associated with each aggregate.
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Additionally, we could implement snapshots of the current data state to improve retrieval speed.
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These snapshots could be taken at intervals, allowing us to quickly access recent states from a database.
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The general advantage here is that it enables us to leverage different kinds of databases for caching as well.
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For instance, relational databases serve effectively for searching and indexing large datasets.
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Conversely, document-oriented databases might be more useful for presenting detailed content.
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Now let’s delve into real-world examples of event sourcing, particularly in e-commerce systems.
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During order and checkout flows, it's crucial to track what actions were taken, making it easy to debug and recalculate state.
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Event sourcing proves valuable in domains dealing with money, as it allows for detailed auditing of transactions.
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It is also applicable in version control systems, like Google Docs, where changes can be rolled back.
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Additionally, tracking systems often utilize event sourcing to calculate statistics about occurrences.
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Regarding frameworks like Redux, it's important to note that event sourcing and event-driven architectures differ.
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In event sourcing, we store events that occurred in the system, while in event-driven architecture, events happen and impact all components.
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A good example of event sourcing can be seen in blockchains, which serve as excellent references for how this architecture functions.
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Now, let’s explore the pros and cons of event sourcing. First, communicating with domain experts is easier.
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We can clearly understand business events since detailed logs can be generated automatically.
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Event sourcing allows us to recover lost system states whenever needed, but this comes at a cost.
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It also shifts developers' mindsets; we no longer think in terms of table-based storage but rather of changes in the system.
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However, event sourcing has drawbacks; it can be complicated to implement and is not popular among some developers.
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Additionally, debugging can be challenging since tracing through numerous events may become cumbersome.
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Version compatibility remains a concern, particularly if migrations require previous versions to be maintained simultaneously.
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In Europe, data privacy regulations also impose restrictions on event management and deletion.
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Now, let’s address some advanced topics in event sourcing.
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When we want to display data as quickly as possible, we can apply two techniques for real-time data presentation.
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The first involves synchronizing the client database with the event database as events occur.
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The second strategy involves using WebSockets or long-polling to keep clients updated on changes in real time.
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Another common question is how to ensure relevance ordering in a multi-application environment.
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We may need to implement distributed locks or other strategies to solve issues of event collisions.
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It’s also essential to think about how to deactivate or delete related events, particularly concerning data privacy.
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Thus, encryption plays a role in preserving sensitive information while allowing for valid deletions.
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If we have event lists, lineage is essential in efficiently retrieving information, like specific user activities.
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We can achieve this by using techniques such as indexed queries and read models.
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Finally, let’s talk about implementing event sourcing in Ruby. The most popular libraries available include Rails Event Store.
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Also, Sequent offers a comprehensive list of features related to event sourcing.
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Additionally, you can build your components if you desire a custom experience, leveraging libraries such as Kafka.
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In regulated industries, incorporating event sourcing guarantees better control over changes, enabling audits and validations.
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As I share this knowledge, using concepts from workshops and stickers has been instrumental in conveying intricate details.
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I also created an experimental repository demonstrating how to implement these techniques effectively.
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In conclusion, while event sourcing can be complex, it provides significant advantages for long-term data management.
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The key is to understand the business events and leverage these techniques to handle complexity in distributed systems.
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Ultimately, though complicated, mastering event sourcing can lead to better data management and clearer insights into application histories.
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I believe event sourcing will become even more relevant in the future, and I encourage you to explore this area further.
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Thank you all for your attention, and I'm happy to take any questions!
