limit_req_zone key cache lifetime

Chad Hansen chadhansen at
Thu Jul 14 19:22:06 UTC 2016

I'm looking for documentation or explanation for how keys expire in the
limit_req_zone. I have the basic documenations here:

*A client IP address serves as a key. Note that instead of $remote_addr,
the $binary_remote_addr variable is used here.
The $binary_remote_addr variable’s size is always 4 bytes for
IPv4 addresses or 16 bytes for IPv6 addresses. The stored state always
occupies 64 bytes on 32-bit platforms and 128 bytes on 64-bit platforms.
One megabyte zone can keep about 16 thousand 64-byte states or about 8
thousand 128-byte states. If the zone storage is exhausted, the server will
return the 503 (Service Temporarily Unavailable) error to all further

But there's no explanation for how the key cache eventually clears itself.
Is any available?
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>

More information about the nginx mailing list