haproxy-healthcheck

haproxy-healthcheck is a tool for usage as agent-check in haproxy's server configuration, reporting back CPU idle time (for usage as weight) or the server's administrative state.

The reported integer percentage is similar to what the vmstat(8) tool reports in its id column when being invoked with a delay of 1 second, like:

% vmstat 1
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 2  0      0 1939504 213764 4155308    0    0    40    64    5    9  9  5 86  0  0
 0  0      0 1942048 213768 4153104    0    0     0    20 2036 5618  7  7 86  0  0
 0  0      0 1941764 213768 4152592    0    0     0    20 2206 5761  7  8 85  0  0
 [...]

The file /var/lib/haproxy-healthcheck/statefile can be used to control the server's administrative state. If the file exists and contains a supported keyword, its content is reported instead of the integer percentage. The following keywords are currently supported:

• down
• drain
• failed
• maint
• stopped
• ready
• up

Note: the optional description strings as well as weights/percentages aren't supported via the file yet. We currently also don't yet support multiple statements in one single line/file.

Note: Do not forget to remove the file to switch back to (live) CPU idle time reporting.

Usage

haproxy-healthcheck relies on systemd socket activation. For testing its integration, you can manually start it to listen on port 2048 via:

% systemd-socket-activate -l 2048 ./haproxy-healthcheck

Installation / Build instructions

Binary packages

Pre-built binary files are available under releases.

Building from source

Make sure to have the build dependencies available:

% sudo apt install gcc libc6-dev golang-go

Then either get the repository via:

% go build -o haproxy-healthcheck github.com/synprosolutions/haproxy-healthcheck

... or to build it from inside the haproxy-healthcheck.git checkout:

% go build -o haproxy-healthcheck ./main.go

System integration

To integrate haproxy-healthcheck, set up an according systemd service unit (adjust /usr/bin/haproxy-healthcheck as needed):

% cat /etc/systemd/system/haproxy-healthcheck.service
[Unit]
Description = HAProxy healthcheck

[Service]
ExecStart = /usr/bin/haproxy-healthcheck
Restart   = always

Set up the corresponding systemd socket unit:

% cat /etc/systemd/system/haproxy-healthcheck.socket
[Socket]
ListenStream = 16000
BindIPv6Only = both

[Install]
WantedBy = sockets.target

Finally start + enable the systemd socket activation:

% sudo systemctl daemon-reload
% sudo systemctl enable --now haproxy-healthcheck.socket

A sample haproxy configuration file which might serve as inspiration or for testing is available.

Author

Michael Prokop, SynPro Solutions GmbH

License

haproxy-healthcheck is licensed under the MIT License. See LICENSE for the full license text.