Server_names scaling

Hi all,

I have spent the day troubleshooting why one server in our network
reloaded
/ tested configuration extremely slowly.

We have found that server_names scales very poorly, once a certain point
is
reached (approx 5.5k entries globally, 5k entries for a single host)
performance drops from a <0.5s reload time to 15s+.

The large host of ~5,000 entries is a malware domain zone and all server
names in this zone are using the wildcard name format.

For now we have resolved this issue by fixing an inefficiency in our
configuration (namely using *.domain.com and domain.com) however I feel
this is most likely a bug or at-least an unintended behaviour.

Relevant configuration entries:
server_names_hash_max_size 8000;
server_names_hash_bucket_size 128;

Regards,
Mathew

Hello!

On Wed, Apr 16, 2014 at 08:38:10PM +1000, SplitIce wrote:

names in this zone are using the wildcard name format.

For now we have resolved this issue by fixing an inefficiency in our
configuration (namely using *.domain.com and domain.com) however I feel
this is most likely a bug or at-least an unintended behaviour.

Relevant configuration entries:
server_names_hash_max_size 8000;
server_names_hash_bucket_size 128;

With max_size 8000, and 5k entries - probability of collisions
while building a cache is high (think of birthday paradox). And
bucket_size 128 isn’t high enough to allow multiple collisions.
As a result, nginx may (and likely will) spend a lot of time trying
to build an optimal hash.

Trivial solution is to use higher max_size and/or bucket_size.


Maxim D.
http://nginx.org/

Thank you, that makes sense and a bit of testing reveals that is
correct.

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