s6-example

Simple example showing the use of s6 as a process supervisor with docker

Running

make build
make run

This will start a container with s6 supervisioning two services: lala and lulu. Each of these services does a single thing: print number - <time> to stdout each second (functionality from /etc/bin/my-binary).

.
├── Dockerfile
├── Makefile
├── README.md
└── etc                   // added to `/etc` of image
    ├── bin
    │   └── my-binary     // main executable
    └── s6
        ├── .s6-svscan    // sv6scan configuration (not a service)
        |   └── finish        // cleans everything on a SIGTERM to PID 1
        ├── lala          // lala service
        │   ├── finish        // lala "on-fail" script
        │   └── run           // lala service start-up script
        └── lulu          // lulu service
            ├── finish        // lulu "on-fail" script
            └── run           // lulu start-up script

Each of the services ( lulu and lala ) have their start-up scripts defined at /etc/s6/<service>/run. Each one of them writes their stdout and stderr to log files, namely, /var/log/<service>; always appending (check the run files!). On a malfunction, /etc/s6/<service>/finish is called. On a termination of the init pid (s6-svscan) ./etc/s6/.s6-svscan is called.

Note: the directory doesn't need to be called /etc/s6, it can be anything. Just make sure that you get the .s6-svscan, run and finish namings right (and no run deeply nested at the scan directory - it will only look on a max depth of 1).