Health checks

The LB Layer4 tab supports the following types of server health checks.

ARP health checks Jump to heading #

When load balancing UDP-based services, you can health check your servers by using the Address Resolution Protocol (ARP) to check whether a server with a given IP address exists on the network.

When you set up ARP health checks, HAProxy ALOHA regularly broadcasts an ARP request to all devices on the network to verify that a server with a given IP address exists. If a matching server does not reply, the health check fails.

1. Select the LB Layer4 tab.

2. Update your configuration in the following ways:

   • Add a check argument to each server line for which you would like to enable health checking.
   • Add option arpcheck in the same section.
   • Add the check directive to the section to configure other options.

   haproxy
   director syslog_servers 10.0.0.9:514 UDP
     balance roundrobin                      # load balancing algorithm
     mode gateway                            # forwarding mode
     option arpcheck
     check interval 5s timeout 1s            # advanced check parameters
     server syslog1 10.0.0.1:514 check
     server syslog2 10.0.0.2:514 check

   haproxy
   director syslog_servers 10.0.0.9:514 UDP
     balance roundrobin                      # load balancing algorithm
     mode gateway                            # forwarding mode
     option arpcheck
     check interval 5s timeout 1s            # advanced check parameters
     server syslog1 10.0.0.1:514 check
     server syslog2 10.0.0.2:514 check

   The option arpcheck directive uses the following syntax:

   text
   option arpcheck [iface <name>]

   text
   option arpcheck [iface <name>]

   Argument	Description
   iface <name> (optional)	Network interface to use when sending the ARP request.

   The check directive uses the following syntax:

   text
   check { [timeout <seconds>] [interval <seconds>] [source <ip>] [port <port>] 
     [rise <count>] [fall <count>] [inhibit] }

   text
   check { [timeout <seconds>] [interval <seconds>] [source <ip>] [port <port>] 
     [rise <count>] [fall <count>] [inhibit] }

   Option	Description
   timeout <seconds>	Period after which an attempt without a response from the server is considered as failed (default: half of interval)
   interval <seconds>	Interval between two checks, in seconds (default: 10 seconds)
   source <ip>	Source IP to use when performing the check
   port <port>	Forces the destination port (default: real server port, if it exists)
   rise <count>	A server will be considered as operational after <count> consecutive successful health checks. The default is 1.
   fall <count	A server will be considered as dead after <count> consecutive unsuccessful health checks. The default is 1.
   inhibit	If a server is down, its weight is passed to 0 but not deleted. Established connection are not broken but new connections are dispatched on the other servers.

ICMP health checks Jump to heading #

When load balancing UDP-based services via the LB Layer4 tab, you can health check your servers by pinging them with the Internet Control Message Protocol (ICMP) to see if they’re up. An ICMP ping sends an echo request packet to the server and then waits for a reply.

When you set up ICMP health checks, HAProxy ALOHA regularly tries to send the server a ping request. If the server does not return a response, the health check fails.

1. Select the LB Layer4 tab.

2. Update your configuration in the following ways:

   • Add a check argument to each server line for which you would like to enable health checking.
   • Add option icmpcheck in the same section. It take no arguments.
   • Add the check directive to the section to configure other options.

   haproxy
   director syslog_servers 10.0.0.9:514 UDP
     balance roundrobin                      # load balancing algorithm
     mode gateway                            # forwarding mode
     option icmpcheck
     check interval 5s timeout 1s            # advanced check parameters
     server syslog1 10.0.0.1:514 check
     server syslog2 10.0.0.2:514 check

   haproxy
   director syslog_servers 10.0.0.9:514 UDP
     balance roundrobin                      # load balancing algorithm
     mode gateway                            # forwarding mode
     option icmpcheck
     check interval 5s timeout 1s            # advanced check parameters
     server syslog1 10.0.0.1:514 check
     server syslog2 10.0.0.2:514 check

   The check directive uses the following syntax:

   text
   check { [timeout <seconds>] [interval <seconds>] [source <ip>] [port <port>] 
     [rise <count>] [fall <count>] [inhibit] }

   text
   check { [timeout <seconds>] [interval <seconds>] [source <ip>] [port <port>] 
     [rise <count>] [fall <count>] [inhibit] }

   Option	Description
   timeout <seconds>	Period after which an attempt without a response from the server is considered as failed (default: half of interval)
   interval <seconds>	Interval between two checks, in seconds (default: 10 seconds)
   source <ip>	Source IP to use when performing the check
   port <port>	Forces the destination port (default: real server port, if it exists)
   rise <count>	A server will be considered as operational after <count> consecutive successful health checks. The default is 1.
   fall <count	A server will be considered as dead after <count> consecutive unsuccessful health checks. The default is 1.
   inhibit	If a server is down, its weight is passed to 0 but not deleted. Established connection are not broken but new connections are dispatched on the other servers.