Nginx Tip - Configure hash bucket size for server names

Nginx is a popular web server and reverse proxy server that is known for its high performance, scalability, and flexibility. It is widely used by many websites and hosting companies, including Server.HK, to handle a large number of concurrent connections and deliver content efficiently. In this article, we will explore a useful Nginx tip - configuring the hash bucket size for server names.

Understanding the hash bucket size

When Nginx receives a request, it needs to determine which server block should handle the request based on the server name specified in the HTTP header. To efficiently handle a large number of server names, Nginx uses a hash table with hash buckets. The hash bucket size determines the number of buckets in the hash table.

The default hash bucket size in Nginx is 64. This means that Nginx will divide the server names into 64 buckets and use a hash function to map each server name to a specific bucket. When a request comes in, Nginx will calculate the hash value of the server name and use it to find the corresponding bucket in the hash table. This allows Nginx to quickly determine the server block that should handle the request.

Why should you configure the hash bucket size?

By default, the hash bucket size of 64 is sufficient for most websites. However, if you have a large number of server names or if you experience a high rate of hash collisions, you may need to increase the hash bucket size to improve performance.

When a hash collision occurs, it means that two or more server names are mapped to the same bucket in the hash table. This can slow down the request handling process because Nginx needs to iterate through all the server names in the bucket to find the correct one. By increasing the hash bucket size, you can reduce the likelihood of hash collisions and improve the efficiency of request handling.

How to configure the hash bucket size

To configure the hash bucket size for server names in Nginx, you need to modify the server_names_hash_bucket_size directive in the Nginx configuration file. This directive specifies the number of hash buckets to use.

Here is an example of how to set the hash bucket size to 128:

http {
    server_names_hash_bucket_size 128;
    ...
}

After making the change, you need to reload or restart Nginx for the new configuration to take effect.

Conclusion

Configuring the hash bucket size for server names in Nginx can help improve the performance of your website, especially if you have a large number of server names or experience a high rate of hash collisions. By increasing the hash bucket size, you can reduce the likelihood of hash collisions and make the request handling process more efficient.

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