Distributed transactions in PHP

With the rapid development of the information age, the e-commerce industry continues to grow, and the corresponding technologies are constantly updated and iterated. Among them, distributed system is one of the mainstream architectures in the current e-commerce industry, which aims to improve the availability and scalability of the system. In distributed systems, transaction processing is an inevitable problem, and distributed transactions are the key to transaction processing. This article will introduce distributed transactions in PHP.

1. Overview of distributed transactions

In a stand-alone environment, a transaction refers to a set of operations, which are either all executed successfully or all canceled. In a distributed environment, transactions need to span multiple nodes to be completed. The operations of each node are as expected, but if any operation fails or fails, the entire transaction will fail. Therefore, a distributed transaction refers to a transaction that runs in a distributed environment.

Distributed transactions can make the system more scalable and highly available, while also improving system performance. However, the implementation of distributed transactions is more complicated, and the object of concern has changed from the data itself to the location of the data, and also involves corresponding communication and coordination processes.

2. Common distributed transaction protocols

Common distributed transaction protocols include Two-phase Commit (2PC) and Three-phase Commit (3PC) .

2PC refers to a two-stage protocol in a distributed environment. In the first phase, the coordinator asks all participants if they are ready to commit the transaction. If all participants are ready, in the second phase, the coordinator asks all participants to commit the transaction. If any participant is not ready, the coordinator will ask all participants to reverse their previous operations.

3PC refers to a three-stage protocol in a distributed environment. The first phase is the same as 2PC, the coordinator asks all participants if they are ready to commit the transaction. If everything is ready, in the second phase, the coordinator asks all participants whether the transaction was successfully committed. If all participants submit successfully, then in the third phase, the coordinator will tell all participants that resources can be released.

3PC has an advantage over 2PC, that is, if any participant does not respond to the request in the first phase, the coordinator will let all participants commit the transaction because it knows whether the participants are ready to commit. affairs. In 2PC, if any participant fails to respond to the request, the coordinator will ask all participants to reverse their previous operations.

3. Distributed transaction implementation in PHP

In PHP, there are many ways to implement distributed transactions, including through distributed transaction middleware, through message queues, through Partial submission and resolution, etc.

1. Solved by middleware

Middleware can merge multiple transactions to form a distributed transaction, thereby protecting the atomicity and consistency of the entire operation, such as TCC (Try, Confirm, Cancel, this model achieves the atomicity of transactions through reserved resources and status checks) and XA (two-phase commit).

Among them, 2PC belongs to XA, but 2PC has problems, such as single point failure of the coordinator, network congestion, timeout and other problems, which can easily lead to blocking and exceptions. The implementation of TCC is relatively simple. It ensures the correct execution of distributed transactions by controlling reserved resources and status.

2. Solve through message queue

Message queue is an emerging technology that can solve transaction problems in distributed systems. Through the message queue, a transaction can be divided into multiple sub-transactions and processed through the queue.

When a sub-transaction is executed successfully, a message is sent to the message queue. This message tells the consumer that the sub-transaction has been completed. If all sub-transactions execute successfully, then the entire transaction is committed, otherwise the entire transaction is canceled.

Distributed transactions implemented through message queues have better performance and reliability, but the implementation is relatively complex and requires labeling and statistics for each sub-transaction.

3. Solve through partial submission

In fact, distributed transaction problems can be solved through partial submission in PHP. The so-called partial submission is to split the original overall submission process into the execution and submission of several sub-tasks.

When each subtask is executed, it only modifies the local transaction and commits it locally, without interacting with other nodes. After all subtasks are executed, wait for the "can commit" signal sent by the outliner, and then commit as a whole to ensure transaction consistency.

4. Summary

PHP is a commonly used programming language and is gradually being used in distributed systems. In distributed systems, transaction processing is an inevitable problem, and distributed transactions are the key to transaction processing. In PHP, distributed transactions can be solved through middleware, through message queues, through local submission, etc. Choosing different methods requires considering the actual application scenarios of distributed transactions, as well as requirements for performance, scalability, and fault tolerance.

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