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Nginx's limit module is used to restrict access to Nginx.

The limit module consists of two parts:

Limit_conn is used to limit the number of connections limit_req is used to limit the frequency of requests

Limit_conn

The implementation of the limit_conn module is simpler than limit_req. Connections with the same variable value are counted directly, and connections that exceed the limit return a 503 error (Service Temporarily Unavailable).

In fact, because there is usually only one pending request on a connection at some point, and because the keepalive and phase handlers cannot determine the state of the connection (new or old), limit_conn uses the number of requests being processed as the number of connections.

This module contains the following sections:

Limit_conn_zone

This configuration item is used to specify the count space for the number of connections.

# Syntax limit_conn_zone [$variable] zone= [zone-name]: [max-storage-space]; # paragraph http# example limit_conn_zone $binary_remote_addr zone=conn_ip:1m

Limit_conn

This configuration item is used to specify the upper limit of the number of connections.

# Syntax limit_conn [zone-name] [max-connections]; # paragraph http, server, location# sample limit_conn conn_ip 10

Limit_conn_status

Optional. This directive was introduced in version 1.3.15. Specifies the http code (status response code) that is returned when the request is rejected.

# Syntax limit_conn_status [http-code]; # paragraph http, server, location# example limit_conn_status 502

Limit_req

Unlike limit_conn, limit_conn directly specifies the upper limit of the number of connections, while limit_req limits the specified upper limit of the rate (that is, frequency) at which the specified variable occurs through the rate parameter.

This module contains the following sections:

Limit_req_zone

This configuration item is used to specify the count space for the frequency of requests.

# Syntax limit_req_zone [$variable] zone= [zone-name]: [max-storage-space] rate= [max-request-rate]; # paragraph http# example # rate=1r/s indicates a limit of only one request limit_req_zone $binary_remote_addr zone=req_ip:1m rate=1r/s per second

Limit_req

This configuration item is used to call the upper limit of frequency specified by limit_req_zone, as well as optional supplementary parameters.

# Syntax # burst is optional. This is followed by an integer indicating the maximum number of requests allowed to exceed the frequency limit. # nodelay is optional. If you do not want more requests to be delayed, you can use the nodelay parameter limit_req zone=req_ip (burst= [numbers]) (nodelay); # paragraph http, server, location# sample limit_req zone=req_ip burst=5 nodelay

Limit_req_status

Optional. It's the same as limit_conn_status. Specifies the http code (status response code) that is returned when the request is rejected.

# Syntax limit_req_status [http-code]; # paragraph http, server, location# example limit_req_status 502

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