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Lazy load services using Socket Activation

linux

Lazy loading services allows services to only be started once they are needed.

This has many system benefits such as:

  1. Speed up startup time: only what is needed is started
  2. Increase linux performance as unused services are not started until they are needed

How it works

I connect to postgres on port 5432. This is the port the socket is listening on. When the socket receives traffic; the socket service will start postgres on port 5433 and proxy traffic from port 5432 to port 5433.

Proxy Socket

The proxy socket listens on an address and once it receives a connection it will activate the Socket Service

Location: /etc/systemd/system/postgresql-proxy.socket

[Socket]
ListenStream=127.0.0.1:5432

[Install]
WantedBy=sockets.target

Socket Service

When this service is started:

  1. The service it is proxying is started
  2. The connection of the socket is proxyed to the actual service
[Unit]
Requires=postgresql.service
After=postgresql.service
Requires=postgresql-proxy.socket
After=postgresql-proxy.socket

[Service]
ExecStart=/lib/systemd/systemd-socket-proxyd 127.0.0.1:5433
PrivateTmp=no
PrivateNetwork=no

Service

This can be considered the actual service which starts the program.

[Unit]
Description=PostgreSQL Server Docker Service

[Service]
Type=simple
ExecStart=/home/john/postgres/run.sh 5433
TimeoutStopSec=5

[Install]
WantedBy=multi-user.target

Finishing up

After creating the <program>.service, <program>-proxy.service and <program>-proxy.socket enable it with the following command:

sudo systemctl enable <program>-proxy.socket

It will automatically work every time upon reboot. You may need to start it this time only to test it

sudo systemctl start <program>-proxy.socket
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