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Is it possible to configure HaProxy to balance traffic for whole subnet. I tried 192.168.50.0/24, but HaProxy gets error. This is for cloud environment, so if my server scales-out, I don't need manually reconfigure HaProxy and restart service.

My Config:

listen Cluster_3300
    bind *:3300
    mode tcp
    timeout client  10800s
    timeout server  10800s
    balance leastconn
    option httpchk
    option allbackups
    default-server port 9200 inter 2s downinter 5s rise 3 fall 2 slowstart 60s maxconn 1424 maxqueue 10000 weight 100
    server app1 192.168.51.11:3306 check
    server app2 192.168.51.13:3306 check
    server app3 192.168.51.12:3306 check

So those last 3 lines is hard coded, is it possible to include all subnet VM's?

Šarūnas Rakauskas
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1 Answers1

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It's not possible and it doesn't make much sense to poll a whole network to see if a server exists or responds.

You can use IPs or hostnames but they will be resolved at startup.

You should add some logic to your cloud scale to add new server to your haproxy load balancer.

From the HAProxy Documentation

server <name> <address>[:[port]] [param*]
Declare a server in a backend

is the internal name assigned to this server. This name will appear in logs and alerts. If "http-send-name-header" is set, it will be added to the request header sent to the server.

is the IPv4 or IPv6 address of the server. Alternatively, a resolvable hostname is supported, but this name will be resolved during start-up. Address "0.0.0.0" or "*" has a special meaning. It indicates that the connection will be forwarded to the same IP address as the one from the client connection. This is useful in transparent proxy architectures where the client's connection is intercepted and haproxy must forward to the original destination address. This is more or less what the "transparent" keyword does except that with a server it's possible to limit concurrency and to report statistics. Optionally, an address family prefix may be used before the address to force the family regardless of the address format, which can be useful to specify a path to a unix socket with no slash ('/'). Currently supported prefixes are : - 'ipv4@' -> address is always IPv4 - 'ipv6@' -> address is always IPv6 - 'unix@' -> address is a path to a local unix socket - 'abns@' -> address is in abstract namespace (Linux only) You may want to reference some environment variables in the address parameter, see section 2.3 about environment variables. The "init-addr" setting can be used to modify the way IP addresses should be resolved upon startup.

is an optional port specification. If set, all connections will be sent to this port. If unset, the same port the client connected to will be used. The port may also be prefixed by a "+" or a "-". In this case, the server's port will be determined by adding this value to the client's port.

is a list of parameters for this server. The "server" keywords accepts an important number of options and has a complete section dedicated to it. Please refer to section 5 for more details.

Examples :

server first 10.1.1.1:1080 cookie first check inter 1000 server second 10.1.1.2:1080 cookie second check inter 1000 server transp ipv4@ server backup "${SRV_BACKUP}:1080" backup server www1_dc1 "${LAN_DC1}.101:80" server www1_dc2 "${LAN_DC2}.101:80"

Federico Galli
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