Development · Programming · Backend
The moment you separate databases for each service, the scope of what can be bound by a single commit ends. When a payment is completed but inventory hasn't decreased, how do you roll it back? This course answers that question with the SAGA pattern.
SAGA is a pattern that breaks down one large transaction into multiple local transactions and reverts them using compensation transactions if a failure occurs.
Where this lecture begins
When it was a single unit
If it fails, the database handles the rollback automatically. There is no need for the developer to intervene.
After dividing the services
Even if the third service fails, the first two have already been committed individually.
In a distributed environment, rollbacks do not happen automatically. we must implement the rollback process through code, and that method is the compensation transaction.
Where this lecture began
A Kakao developer serving as an interviewer brought up this topic first.
The Kakao interviewer brought up the topic first.
What SAGA does
Processing a single order involves multiple services. Each service commits a local transaction to its own database. If a failure occurs in the middle, a series of cancellation tasks are executed in reverse order to undo the previously successful steps.
There isn't just one way to undo changes. The Rollback provided by the database and the Compensation we create are different things, and we will start by addressing those differences in Section 4.
What you will learn
Two types of implementations
There are two main ways to implement SAGA. This is also the point where opinions differ most frequently in interviews.
You won't just learn one of the two. In Section 3, we will compare the success and failure flows along with the pros and cons of each, and in the final section, we will build the same example using both methods.
Practice Environment
We will create the electronic payment example by dividing it into three applications. The environment will be launched all at once using Docker Compose.
Both skeleton code and the completed version are included in the materials. If you find it burdensome to type everything from scratch, you can start with the skeleton code.
It doesn't end with just theory.
In the final section, we will personally build three applications and run them in two different ways.
커리큘럼 보기Curriculum
In the first half, we identify why it becomes a problem and establish the patterns; in the second half, we set up the environment and implement it ourselves.
For people like this
The current market
New hiring is decreasing, and companies are trying to hire only those who are proven. These are articles that have come out in the past few months.
As companies become more anxious, those being hired must demonstrate a clearer distinction. Ultimately, studying is something you do on your own, but depending on what you look at and from which perspective, the depth of what you can explain changes even when spending the same amount of time. I created this lecture to pass on that very perspective.
Course Reviews
I copied this directly from the Inflearn course reviews.
"I really enjoyed the lecture. I loved the overall architecture and the accompanying explanations shown through numerous diagrams at the beginning, and I could also check the lecture summary file for any knowledge I might have lacked or concepts that needed organizing. Furthermore, the process of reviewing was explained step-by-step, and I found the realistic stories and practical perspectives to be very beneficial."
Crazy about development · Written after 92% completion
"Personally, I think this might be one of the most informative courses on Inflearn. The content was very substantial and helpful for my learning. Thank you."
keny · Written after 92% completion
"It was a great time to study distributed transactions!"
Pairi2 · Written after 100% completion
Instructor
It was co-created by Choi, a 12-year developer who develops servers at Kakao headquarters and also serves as an interviewer, and Hong, a platform server developer in Pangyo.
I am a 12-year backend developer building servers at Kakao headquarters, and I also serve as an interviewer. In interviews, I focus more on whether a candidate can design systems rather than their knowledge of programming syntax. I have incorporated that exact perspective into this lecture.
"I rarely ask about programming syntax in interviews. I look for whether you can design."
Current Kakao HQ Server Developer · Interviewer · Computer Science Major
I am in charge of platform server development in Pangyo. I continue my activities as a knowledge sharer to share the methods I studied myself and the problems and solutions encountered in practice. The lectures are not created alone, but together with several developers currently working in the field.
"Dividing services is easy, but handling failures after they are divided is difficult."
Frequently Asked Questions
After dividing services, what is needed is not a larger transaction, but a different design.
결정하기 전에 커리큘럼 다시 훑어보기Let's talk together
It takes a long time when you're stuck alone. There is a separate space where you can comfortably share everything from parts you get stuck on while taking lectures, questions that arise while applying them to your own service, to stories about your career and the industry.
We discuss real-world problems encountered in practice, the architectures others have chosen, and stories about developer careers. Questions related to the lectures are also welcome.
"The spots where you get stuck are usually where others get stuck too. Asking someone who has already passed through is the fastest way."
I'm helping create this course and work as a server developer at Kakao. Actually, I wanted to hide the fact that I'm an interviewer... 😭😭 But I thought this would be such a great topic to cover, so I decided to join this course. As I mentioned, when I actually conduct interviews at Kakao, I'm not particularly curious about things from a programming perspective. Most of my questions focus on whether someone can do architectural design, and I consider `what kind of concepts this person can come up with` to be extremely important. Various problems can arise from this perspective, and one of those factors is distributed transactions. That's why I think this course is all the more beneficial. If you can answer these kinds of questions after taking this course, I think you'll have learned something truly meaningful. 1. Please tell me about the two patterns of SAGA (Choreography VS Orchestration) 2. Please tell me about the differences and pros/cons of these two patterns. I'm particularly curious about throughput and the problems that come with it. 3. Do you know the concept of local transactions?? (If you don't know, I'll explain it) Then how can distributed transactions be managed in relation to these transactions?? 4. Please tell me everything you know about distributed transactions in general. I'm curious. 5. Do you know what the Database per Service perspective is?? These are examples of questions I actually ask when I go into interviews. If you know about these areas and can answer them, it would be a great help. Please show a lot of interest in the course. Thank you!
It's theory-focused. I'd say it's about 80% theory and 20% practice. It doesn't seem suitable for those who want to learn theory and see real-world source code examples. However, it's suitable for those who know nothing about patterns.
I personally think this might be one of the most beneficial lectures on Inflearn. The content was so substantial that I was able to learn a lot from it. Thank you.
It was good for establishing a general framework.
Thank you so much for the informative lecture.
