Our AI writing assistant, WriteUp, can assist you in easily writing any text. Click here to experience its capabilities.

System Design: Distributed Transactions

View Original View Raw

Summary

This article is part of a System Design Course available on Github, and focuses on distributed transactions. A distributed transaction is a set of operations on data that is performed across two or more databases, and is typically coordinated across separate nodes connected by a network. The article discusses two popular solutions for distributed transactions: the two-phase commit (2PC) protocol and the three-phase commit (3PC) protocol. It also covers the Saga pattern, which is a sequence of local transactions, and discusses the two common implementation approaches of choreography and orchestration.

Q&As

What is a distributed transaction?
A distributed transaction is a set of operations on data that is performed across two or more databases.

How does the two-phase commit protocol work?
The two-phase commit (2PC) protocol is a distributed algorithm that coordinates all the processes that participate in a distributed transaction on whether to commit or abort (roll back) the transaction. This protocol requires a coordinator node, which basically coordinates and oversees the transaction across different nodes. The coordinator tries to establish the consensus among a set of processes in two phases, hence the name. The two phases are the Prepare phase and the Commit phase.

What is the three-phase commit protocol?
Three-phase commit (3PC) is an extension of the two-phase commit where the commit phase is split into two phases. This helps with the blocking problem that occurs in the two-phase commit protocol. The three phases are the Prepare phase, the Pre-commit phase, and the Commit phase.

What is a saga?
A saga is a sequence of local transactions. Each local transaction updates the database and publishes a message or event to trigger the next local transaction in the saga.

What are the advantages of using the three-phase commit protocol?
The Pre-commit phase accomplishes the following: If the participant nodes are found in this phase, that means that every participant has completed the first phase. The completion of prepare phase is guaranteed. Every phase can now time out and avoid indefinite waits.

AI Comments

👍 This article provides an in-depth look at distributed transactions and is an incredibly useful resource for those looking to learn more about system design.

👎 This article is overwhelming with its 57 part series and could use more visual elements to make the content easier to understand.

AI Discussion

Me: It's about distributed transactions. It discusses the need for them, different solutions like two-phase commit and three-phase commit, and the implications of using sagas and choreography and orchestration for coordination.

Friend: Wow, that sounds really interesting. What are the implications of using this system?

Me: Well, implementing distributed transactions can be complicated, as the database must coordinate the committing or rollback of the changes in a transaction as a self-contained unit. Also, two-phase commit is not resilient to all possible failure configurations, and three-phase commit solves the blocking problem of two-phase commit but is hard to debug and test. Additionally, using sagas and choreography or orchestration for coordination can pose durability challenges and risk of cyclic dependency.

Action items

Research the two-phase commit and three-phase commit protocols in more detail.
Explore the pros and cons of the Saga pattern for distributed transactions.
Experiment with different implementation approaches for distributed transactions, such as choreography and orchestration.

Technical terms

Distributed Transactions: A distributed transaction is a set of operations on data that is performed across two or more databases. It is typically coordinated across separate nodes connected by a network, but may also span multiple databases on a single server.
Two-Phase Commit: The two-phase commit (2PC) protocol is a distributed algorithm that coordinates all the processes that participate in a distributed transaction on whether to commit or abort (roll back) the transaction.
Three-Phase Commit: Three-phase commit (3PC) is an extension of the two-phase commit where the commit phase is split into two phases.
Sagas: A saga is a sequence of local transactions. Each local transaction updates the database and publishes a message or event to trigger the next local transaction in the saga.
Choreography: Choreography is an implementation approach where each local transaction publishes domain events that trigger local transactions in other services.
Orchestration: Orchestration is an implementation approach where an orchestrator tells the participants what local transactions to execute.