fastcgi_busy_buffers_size
The `fastcgi_busy_buffers_size` directive sets the size of the busy buffers used by FastCGI to buffer responses from an upstream server.
Description
In NGINX, the fastcgi_busy_buffers_size directive defines the maximum size of the FastCGI buffering space that can be utilized for responses being processed. This memory allocation is critical for managing how FastCGI buffers data being sent from the upstream server before it is transmitted back to the client. When the size specified by fastcgi_busy_buffers_size is reached, NGINX will either start sending buffered responses to the client or handle the traffic differently based on the configured settings.
The directive accepts a single argument that specifies the size of the busy buffers in bytes. If the allocated buffer is insufficient, NGINX can be configured to either delay the processing or manage how the data flows, ensuring that responses are appropriately ordered and successfully delivered. This directive can influence performance, especially under heavy load scenarios, where too small a buffer could lead to degraded response times and increased latency, as NGINX may need to frequently flush buffers to accommodate incoming data.
For optimal performance, it is advisable to consider the expected maximum response sizes from the upstream server and the typical load on the NGINX server when configuring this directive. Misconfiguration can result in performance bottlenecks, hence monitoring and testing are essential to find the right buffer sizes for your specific application needs.
Config Example
http {
server {
location /api {
fastcgi_pass 127.0.0.1:9000;
fastcgi_busy_buffers_size 16k;
include fastcgi_params;
}
}
}Setting the size too low can lead to increased latency as NGINX flushes buffers more frequently.
Conflicting settings with fastcgi_buffer_size can result in inefficient memory usage.
Not adjusting the buffer size according to the typical load can lead to performance issues.