Upstream module directives
ip_hash
Ensures the distribution of connecting clients evenly over
all servers by hashing the IP address, keying on its class-C
network.
keepalive
The number of connections to upstream servers that
are cached per worker process. When used with HTTP
connections, proxy_http_version should be set to 1.1
and proxy_set_header to Connection "".
least_conn
Activates the load-balancing algorithm where the server
with the least number of active connections is chosen for
the next new connection.
server
Defines an address (domain name or IP address with an
optional TCP port, or path to a UNIX-domain socket)
and optional parameters for an upstream server. The
parameters are:
weight: It sets the preference for one server over
another
max_fails: It is the maximum number of
unsuccessful communication attempts to a server
within fail_timeout before the server is marked
as down
fail_timeout: It is the length of time a server
has to respond to a request and the length of time
a server will be marked as down
backup: It will only receive requests once the
other servers are down
down: It marks a server as not able to
process requests
The keepalive directive deserves special mention. NGINX will keep this number of
connections per worker open to an upstream server
Memcached upstream servers
upstream memcaches {
server 10.0.100.10:11211;
server 10.0.100.20:11211;
}
server {
location / {
set $memcached_key "$uri?$args";
memcached_pass memcaches;
error_page 404 = @appserver;
}
location @appserver {
proxy_pass http://127.0.0.1:8080;
}
}
The memcached_pass directive uses the $memcached_key variable to make the key
lookup. If there is no corresponding value ( error_page 404 ), we pass the request
on to localhost , where there is presumably a server running that will handle this
request and insert a key/value pair into the memcached instance
Determining the client's real IP address
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
