nginx limit the number of connections (ngx_http_limit_conn_module) module nginx concat module echo nginx module nginx upsync module

ngx_http_limit_conn_module limits the number of concurrency for some servers with abnormal traffic, excessive load, or even large-traffic malicious attack access; this module can limit the number of connections for each key value based on the defined key, only those that are being used Connections that handle requests for which the header information has been fully read are counted.

This module provides two configuration parameters, limit_conn_zone and limit_conn. Limit_conn_zone can only be configured in the http{} section, while limit_conn can be configured in the http{}, server{}, and location{} sections.

---

1. limit_conn_zone

Syntax: limit_conn_zone $variable z
Configuration section: http

This directive describes the session state storage area. The current number of connections is saved in the key's state, and the value of the key can be any non-null value of a specific variable (null values ​​are not considered). $variable defines the key, z defines the area name, and its main function is the limit_conn that follows. size defines the shared memory space size of each key, such as:

Note:

The IP address of the client is used as the key. Note that the binary_remote_addr variable is used here, not the remote_addr variable.
The length of the remote_addr variable ranges from 7 bytes to 15 bytes, while the storage state occupies 32 bytes or 64 bytes in 32-bit platforms and 64 bytes in 64-bit platforms.
The length of the binary_remote_addr variable is fixed 4 bytes, and the storage state occupies 32 bytes or 64 bytes on 32-bit platforms, and 64 bytes on 64-bit platforms.
1M shared space can save 32,000 32-bit states and 16,000 64-bit states.
If the shared memory space is exhausted, the server will return a 503 (Service Temporarily Unavailable) error to all subsequent requests.

---

2. limit_conn

Syntax: limit_conn zone_name number
Configuration section: http, server, location

This directive specifies the maximum number of simultaneous connections for each given key value. When this number is exceeded, a 503 (Service) error is returned. For example (the same IP is only allowed to have 20 connections at the same time):

---

3. Configuration and usage examples

limit_conn_zone $binary_remote_addr z
Mainly used to define variables, zone names, and shared memory sizes

limit_conn showjoy_conn 20;
Configure the showjoy_conn defined earlier, and limit the number of concurrent connections for the same IP to 20

---

4. Precautions for use

Transactions have two sides. Although the ngx_http_limit_conn_module module can solve the current concurrency problems, it will introduce other problems. For example, if the front-end does LVS or reverse generation, and our back-end enables this module function, wouldn't there be a lot of 503 errors? In this case, you can enable the module on the front end, or set a whitelist.

Module address: https://yunpan.cn/cqSKP6BrJ2AeT Access password 4f50

').addClass('pre-numbering').hide(); $(this).addClass('has-numbering').parent().append($numbering); for (i = 1; i ').text(i)); }; $numbering.fadeIn(1700); }); });

The above introduces the nginx limit connection number (ngx_http_limit_conn_module) module, including module and nginx content. I hope it will be helpful to friends who are interested in PHP tutorials.