hongquan / wait-server

Tool to wait for a server to be online

wait-server

Tool (as Bash script) to wait for a server to be online (connectable), in a certain duration.

Usage

wait-server 8000

is to wait for a server at port 8000, on localhost to be online. After 5 seconds, the program will exit with error.

Full options:

wait-server [[HOST] PORT] [-t <timeout>][-q][-h]

where:

• HOST: Host name or IP address of server. Default is localhost.
• PORT: Port where the server is listening. Default is 8000.
• t: Timeout. Default is 5s.
• q: Quiet, don't show progress dots.

Main purpose of this tool, is to be used in a systemd service, to delay the service until some server is online. For example, you have service-a and service-b, in which service-a is a server software that takes long time to initialize (often Java application), and service-b should be run only after service-a is ready. You can write the systemd service file like this:

[Unit]
After=service-a.service

[Service]
ExecStartPre=/usr/bin/wait-server
ExecStart=/usr/bin/application-b

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