ReactPHP HttpServer: Warning: stream_select(): You MUST recompile PHP with a larger value of FD_SETSIZE.

[wilaak]

I am running a Server-Sent Events (SSE) application with many keepalive connections using ReactPHP HttpServer. When scaling up the number of concurrent connections, I encounter the following warning:

PHP Warning:  stream_select(): You MUST recompile PHP with a larger value of FD_SETSIZE.
It is set to 1024, but you have descriptors numbered at least as high as 1024.
 --enable-fd-setsize=2048 is recommended, but you may want to set it
to equal the maximum number of open files supported by your system,
in order to avoid seeing this error again at a later date

What is the recommended way to increase this limit for high-concurrency SSE applications with ReactPHP HttpServer?

[wilaak]

Yeah I just answered myself, installing the ext-ev extension seemed to fix the issue:

To install the ext-ev extension, follow these steps:

---

On Ubuntu/Debian

1. Install via PECL:

   sudo pecl install ev

2. Enable the extension:
   Add the following line to your php.ini (you can find the location with php --ini):

   extension=ev.so
   

---

Verify Installation

Run:

php -m | grep ev

You should see ev in the output.

[clue]

@wilaak Thanks for sharing your answer so others can benefit from this! I agree with your proposed solution to install ext-ev would be the way to go, though specifics may vary depending on the platform used. For reference, here are the relevant links to our documentation: https://github.com/reactphp/event-loop#loop-implementations and https://framework-x.org/docs/best-practices/deployment/#fd-limits.