|conn |required|is the maximum number of concurrent requests allowed. Requests exceeding this ratio (and below `conn` + `burst`) will get delayed to conform to this threshold.|
|burst |required|is the number of excessive concurrent requests (or connections) allowed to be delayed.|
|default_conn_delay |required|is the default processing latency of a typical connection (or request).|
|key |required|is the user specified key to limit the concurrency level. <br>For example, one can use the host name (or server zone) as the key so that we limit concurrency per host name. Otherwise, we can also use the client address as the key so that we can avoid a single client from flooding our service with too many parallel connections or requests. <br> Now accept those as key: "remote_addr"(client's IP), "server_addr"(server's IP), "X-Forwarded-For/X-Real-IP" in request header.|
|rejected_code |required| The HTTP status code returned when the request exceeds the threshold is rejected. The default is 503.|
You can open dashboard with a browser: `http://127.0.0.1:9080/apisix/dashboard/`, to complete the above operation through the web interface, first add a route:
The parameters of the plugin enabled above indicate that only one concurrent request is allowed. When more than one concurrent request is received, will return `503` directly.
