Help:: Listen queue overflow killing servers

David Christensen dpchrist at
Fri Jul 26 16:12:06 UTC 2019

On 7/26/19 4:58 AM, Paul Macdonald via freebsd-questions wrote:
> Over the past few months i've seen several boxes (4 or 5) become 
> unresponsive as a result of a Listen queue overflow state.

> All are on ZFS and are std apache/php/mysql servers with nothing too 
> exotic.

> /var/log/messages shows tyically;
>      kernel: sonewconn: pcb 0xfffff813395e3d58: Listen queue overflow: 
> 193 already in queue awaiting acceptance (83 occurrences)
> netstat -Lan  shows
> tcp4 193/0/128                          x.x.x.x.443
> tcp4  193/0/128                          x.x.x.x.80

What Apache/ PHP/ MySQL applications?  Did you write them?  If not, who 
did?  Is everything up to date?  Have you filed bug reports?

Do the applications have logging or debugging capabilities?  Have you 
enabled them?  What do they say?  Where is the blockage?  Deadlock?


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