HAProxy Configuration: Difference between revisions
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The source IP address is hashed and divided by the total weight of the running servers to designate which server will receive the request. This ensures that the same client IP address will always reach the same server as long as no server goes down or up. If the hash result changes due to the number of running servers changing, many clients will be directed to a different server. This algorithm is generally used in TCP mode where no cookie may be inserted. It may also be used on the Internet to provide a best-effort stickiness to clients which refuse session cookies. This algorithm is static by default, which means that changing a server's weight on the fly will have no effect, but this can be changed using "hash-type". | |||
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Revision as of 23:21, 4 July 2017
Internal
Overview
If installed with yum, the default configuration file is deployed in /etc/haproxy/haproxy.cfg and the systemd configuration file in /etc/sysconfig/haproxy.
Dependency on Other Services
Under some circumstances, HAProxy need other services to start before it starts, so it can rely on them. For example, if a local DNS server resolves the names referred from HAProxy configuration file, the named service must start before HAProxy. This is configured in the HAProxy's unit file /usr/lib/systemd/system/haproxy.service:
Requires=named.service After=syslog.target network.target named.service
More details: Declaring a Dependency on a Service.
Logging Configuration
HAProxy logging concepts:
Logging configuration consists of the following steps:
Add the following to the "global" section of the configuration file:
log 127.0.0.1:514 local2
and then add the following to each "defaults" section or to each frontend and backend section:
log global
Then make sure the local syslogd does listen to the UDP traffic. For details on how to do this for rsyslogd, see:
Configure HAProxy to Log into a File
Assuming that logging was configured as described in the previous section, configure local2 events to go to the /var/log/haproxy.log file. Add the following line in /etc/rsyslog.conf:
local2.* /var/log/haproxy.log
SSL Configuration
Configuration Reference
Options
httplog
tcplog
Logging is set to tcp instead of the default http.
ssl-hello-chk
A health check that verifies the the connection and its ability to handle SSL (SSLv3 specifically) connections.
global
defaults
mode
Possible values:
http
tcp
Used to pass secure connections off to a backend server without encrypting it.
balance
Specifies the algorithm used to select a server when doing load balancing. This only applies when no persistence information is available, or when a connection is redispatched to another server. Possible values:
roundrobin
Each server is used in turns, according to their weights. This is the smoothest and fairest algorithm when the server's processing time remains equally distributed. This algorithm is dynamic, which means that server weights may be adjusted on the fly for slow starts for instance. It is limited by design to 4095 active servers per backend.
source
The source IP address is hashed and divided by the total weight of the running servers to designate which server will receive the request. This ensures that the same client IP address will always reach the same server as long as no server goes down or up. If the hash result changes due to the number of running servers changing, many clients will be directed to a different server. This algorithm is generally used in TCP mode where no cookie may be inserted. It may also be used on the Internet to provide a best-effort stickiness to clients which refuse session cookies. This algorithm is static by default, which means that changing a server's weight on the fly will have no effect, but this can be changed using "hash-type".