Linux distributions use systemd to initialize the user space and subsequently manage all processes.

Note

This section does not apply to Ubuntu 14.04 because it does not use systemd. Other Linux distributions rely on init scripts

The table below summarizes the services that systemd manages directly and the ones that sysv manages. The service list may change based on the subscription level and installed packages.

Service

Init system

hapee-1.9

sysv

hapee-1.9-lb

systemd

hapee-extras-rhi

sysv

hapee-extras-route

sysv

hapee-extras-snmp

sysv

hapee-extras-vrrp

sysv

Note

The commands listed here apply to both services managed by systemd or sysv.

Interaction between systemd and HAProxy

When a system uses systemd, the following process unfolds:

  1. systemd starts a wrapper process, which handles communication between systemd and HAProxy. This wrapper process name is hapee-lb-systemd-wrapper.

  2. hapee-lb-systemd-wrapper then parses the configuration file and starts up a new process called hapee-lb-master. Its role is to parse and load the configuration file and to create the required number of HAProxy processes.

  3. Running HAProxy processes are called hapee-lb.

The process basically gives us the following cgroup tree. A cgroup (abbreviated from control groups) is a Linux kernel feature that limits, accounts for, and isolates the resource usage (CPU, memory, disk I/O, network, etc.) of a collection of processes.

Main PID: PID from (hapee-lb-systemd-wrapper)
CGroup: /user/system.slice/hapee-1.9-lb.service
 |-PID /opt/hapee-1.9/sbin/hapee-lb-systemd-wrapper ...
 |-PIDa /opt/hapee-1.9/sbin/hapee-lb-master
 |-PIDb /opt/hapee-1.9/sbin/hapee-lb ...
 |-PIDc /opt/hapee-1.9/sbin/hapee-lb ...

systemd sends signals to hapee-lb-systemd-wrapper. This process propagates its environment to its descendants. When a reload occurs, hapee-lb-systemd-wrapper itself is not reloaded, but passes the information to hapee-lb-master to run the reload operation.

Enable a service

By default, the services installed with HAProxy Enterprise are not enabled.

To enable a service run systemctl enable <service name>

Output when enabling a systemd based service:

# systemctl enable hapee-1.9-lb
Created symlink from /etc/systemd/system/multi-user.target.wants/hapee-1.9-lb.service to /usr/lib/systemd/system/hapee-1.9-lb.service.

Start a service

To start a service run systemctl start <service name>

systemctl start hapee-1.9-lb

Stop a service

To stop a service run systemctl stop <service name>

To stop hapee-1.9-lb:

systemctl stop hapee-1.9-lb

Restart a service

To restart a service run systemctl restart <service name>

Example to restart hapee-1.9-lb:

systemctl restart hapee-1.9-lb

Reload a service

To reload a service run systemctl reload <service name>

Example to reload hapee-1.9-lb:

systemctl reload hapee-1.9-lb

Warning

systemd has a severe limitation concerning reload: the environment variables do not get reloaded during a service reload. You must perform a service restart.

The reason is because hapee-lb-systemd-wrapper loads environment variables at startup, and these cannot get refreshed at reload. See Interaction between systemd and HAProxy.