How to perform distributed transaction processing in PHP?

With the continuous development of Internet applications, distributed systems have become more and more common. In a distributed system, a transaction may involve multiple components or services, which brings about the problem of distributed transaction processing. As a commonly used server-side programming language, PHP also needs to solve distributed transaction processing problems. In this article, we will discuss how distributed transactions are done in PHP.

1. What is distributed transaction processing?

In a traditional stand-alone environment, transaction processing is very simple. Under normal circumstances, a transaction only needs to connect to the database, perform operations such as inserting, updating, or deleting data, and then commit or rollback the transaction. However, in a distributed system, a transaction involves multiple components or services. At this time, it is necessary to ensure that all components or services can successfully submit or roll back the transaction to ensure transaction consistency.

2. Distributed transaction processing in PHP

In PHP, we usually use a database to store data. Therefore, we need to find a way to maintain consistency in transaction operations between multiple databases. Traditional MySQL only supports local transactions, but we can use the XA protocol to implement cross-database transactions.

XA protocol is a distributed transaction protocol that allows multiple databases to participate in the same transaction. The XA protocol is divided into two phases: prepare and commit.

In the prepare phase, all transaction participants must give "agree" or "disagree" responses to the commit or rollback of the transaction. These responses will be collected by a global transaction coordinator. If all transaction participants agree to commit the transaction, the commit phase is entered; if one participant disagrees, the rollback phase is entered.

In the commit phase, all participants must submit local transactions to the local database to ensure the atomicity of the transaction.

3. XA interface in PHP

In PHP, we can use the XA interface to implement the XA protocol. The following are some key XA interface functions:

• XA_START: To start an XA distributed transaction, the preparation operations of all participants must be coordinated at the beginning.
• XA_END: ​​Ends an XA distributed transaction. This function will not commit or rollback the transaction.
• XA_PREPARE: Perform a prepare operation on a participant. This operation does not commit or rollback the transaction.
• XA_COMMIT: Submit an XA distributed transaction.
• XA_ROLLBACK: Roll back an XA distributed transaction.
• XA_RECOVER: Recover unfinished XA distributed transactions after restart.

4. Sample code

The following is a simple PHP program to demonstrate how to use the XA interface to implement distributed transaction operations:

$mysql1 = new mysqli("localhost", "username1", "password1", "database1");
$mysql2 = new mysqli("localhost", "username2", "password2", "database2");

//开始一个XA事务
$xa = mysqli_init();
$conn1 = mysqli_real_connect($xa, "localhost", "username1", "password1", "database1");
$conn2 = mysqli_real_connect($xa, "localhost", "username2", "password2", "database2");
$xid = uniqid('', true);
mysqli_autocommit($xa, FALSE);
mysqli_begin_transaction($xa, MYSQLI_TRANS_START_WITH_XID, $xid);

//对数据库1进行操作
mysqli_query($mysql1, "INSERT INTO table1 (value) VALUES ('test')");

//对数据库2进行操作
mysqli_query($mysql2, "INSERT INTO table2 (value) VALUES ('test')");

//准备提交事务
$xares1 = mysqli_prepare($xa, "XA PREPARE '$xid'");
$xares2 = mysqli_prepare($xa, "XA PREPARE '$xid'");

if (mysqli_stmt_execute($xares1) && mysqli_stmt_execute($xares2)) {
    //提交事务
    $xacmt1 = mysqli_prepare($xa, "XA COMMIT '$xid'");
    $xacmt2 = mysqli_prepare($xa, "XA COMMIT '$xid'");
    if (mysqli_stmt_execute($xacmt1) && mysqli_stmt_execute($xacmt2)) {
        //事务提交成功
        mysqli_commit($mysql1);
        mysqli_commit($mysql2);
    } else {
        //事务提交失败
        mysqli_rollback($mysql1);
        mysqli_rollback($mysql2);
    }
} else {
    //准备操作失败
    mysqli_rollback($mysql1);
    mysqli_rollback($mysql2);
}

//关闭数据库连接
mysqli_close($mysql1);
mysqli_close($mysql2);

5. Summary

Distributed transaction processing is a core issue in modern applications. In PHP, we can use XA interface to achieve this. By implementing the XA protocol, we can ensure the consistency of transaction operations between multiple databases. Using the XA interface requires a certain technical foundation, but after becoming familiar with it, we can easily implement distributed transaction processing.

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