Vertical scaling in PHP

With the continuous advancement of Internet technology, the number of users of Web applications continues to increase, and the performance requirements for servers are also getting higher and higher. If multiple servers are used for load balancing, the performance and reliability of Web applications can be improved to a certain extent, but the cost will also increase exponentially. Therefore, how to improve the performance of a single server has become the focus of web application developers and operation and maintenance personnel. In this case, vertical scaling became a widely adopted solution.

Vertical expansion is to improve the performance of the server by increasing the hardware resources of a single server, such as CPU, memory, disk, etc. Compared with horizontal expansion (increasing the number of servers), vertical expansion is simpler and more direct. It does not require large-scale adjustment and reconstruction of the existing system. At the same time, there are some risks and challenges.

In PHP applications, vertical expansion solutions mainly involve the following aspects:

1. CPU

In the era of multi-core CPUs, PHP applications use Multi-thread or multi-process to fully utilize the performance of multi-core CPU. For example, the PHP-FPM extension provides a multi-process management mechanism that can create multiple independent processes according to different user requests to improve the performance of PHP applications.

In addition to the multi-process mechanism, you can also utilize the multi-core resources of the CPU by writing multi-threaded code. However, since PHP is an interpreted scripting language, it is not suitable for writing complex multi-threaded code, and PHP's thread safety is not very good. Therefore, multi-process scenarios are more common.

2. Memory

When PHP applications process large amounts of data, the problem of excessive memory usage often occurs. If the server has insufficient memory, it can cause PHP applications to run slowly or crash. In order to solve this problem, you can improve the performance of PHP applications by increasing the memory capacity of the server.

In addition, PHP’s garbage collection mechanism will also affect memory usage. You can optimize the performance and memory usage of PHP applications by adjusting the parameters of the PHP garbage collection mechanism. For example, you can adjust the gc_probability and gc_divisor parameters in the php.ini configuration file to control the triggering probability and efficiency of the garbage collection mechanism.

3. Disk

PHP applications often require reading and writing large amounts of data, such as database access, file upload and download, etc. These operations may become a performance bottleneck for PHP applications. In order to improve the disk IO performance of PHP applications, it can be optimized in the following ways:

• Use high-performance disk storage devices, such as solid-state drives (SSD);
• Use cache Technologies, such as Memcached, Redis, etc., cache frequently read and written data into memory to reduce the number of disk IO operations;
• Optimize the code and algorithm of PHP applications to reduce unnecessary disk IO operations;
• Adopt event-driven architecture, such as Swoole extension, to convert PHP applications into asynchronous IO models to avoid blocking IO operations.

4. Network

The network IO performance of PHP applications is mainly affected by factors such as network bandwidth and latency. If your application needs to handle a large number of network requests, you need to consider how to improve network IO performance.

In order to optimize network IO performance, the following methods can be used:

• Use high-performance servers and network equipment to increase bandwidth and speed;
• Change static Resources such as images, CSS, JS, etc. are hosted on CDN to reduce the server's processing of these resources;
• Optimize network protocols and communication models to reduce network delays and data transmission time;
• Use Websocket Equal-length connection technology reduces overhead such as network handshakes.

When performing vertical expansion of PHP applications, it is necessary to implement the two principles of "optimizing bottlenecks" and "stability". Optimizing bottlenecks can improve application performance, but you need to be careful not to over-optimize, which will affect the stability and reliability of the system. Stability is a key element for vertical expansion. The high availability and fault tolerance of the system must be ensured to avoid single points of failure. To do this, adequate testing and risk assessment are required to determine the appropriate vertical expansion solution.

In short, vertical expansion is an effective solution to improve the performance of a single server, and it has also been widely used in PHP applications. By increasing CPU, memory, disk and network resources, the performance and reliability of PHP applications can be improved to meet user needs and service requirements.

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