K6 Soak Tests: Too Many Open Files

Soak tests with k6 might generate this error:

ERRO[0543] GoError: dial tcp 1.2.3.4:443: socket: too many open files
running at go.k6.io/k6/js/modules/k6/ws.(*WS).Connect-fm (native)

Indicating a hard limit imposed by the Linux kernel, as the k6 process was trying to establish a lot of simultaneous connections.

This error can relate to personal file descriptor limits:

% ulimit -n
1024

The fix was simple:

% ulimit -n 10000

And to verify:

% ulimit -n
10000