"Could not build the server_names_hash, you should increase server_names_hash_bucket_size: 32"

 Just restarted nginx, result , The service doesn't work , Go to the error log file and have a look , result , I found this mistake ：
could not build the server_names_hash, you should increase server_names_hash_bucket_size: 32

 I searched the related posts , quite a lot , The solution is simple , Is in the  http layer , Add the following ：
server_names_hash_bucket_size 64; #64 This value , It can be adjusted accordingly 

 The reason for this error is ： because Nginx Medium server Configuration in progress server_name The definition value of is too long ！

 What then? Server_name Too long will cause this problem , That's the key ：

 Server name hash The table is ordered by  server_names_hash_max_size  and  server_names_hash_bucket_size Controlled by .

 according to Nginx Analysis of official documents ,server_names_hash_bucket_size The default value of may be 32 It could be 64, Or some other value , The size of this default value depends on CPU Cache line length of .

 Parameters hash bucket size Always equal to hash The size of the table , And it's a multiple of the cache size of the processor along the way .

 After reducing the number of accesses in memory , Speed up the search in the processor hash Table key values become possible .

 If  hash bucket size Equal to the size of the processor cache , So when it comes to finding keys , In the worst case, the number of lookups in memory is 2. The first time is to determine the address of the storage unit , The second time is to find the key value in the storage unit . therefore , If Nginx Give the need to increase  hash max size  or  hash bucket size A hint of , So the first thing is to increase the size of the previous parameter .