how to start customized and automated cron

Question

I'm creating a site in php, which analyzes instagram profiles such as number of followers, likes etc. now I want to create a sort of grid where the number of followers are stored every day, so as to have a grid with the number of daily followers at the end of the month I thought of creating a cron with a script that saves me the number of followers every day on a database, but obviously I cannot save the data of all instagram users on the database, but to save them only when the user in question is searched , I don't know if I explained myself well so I give an example:

I look for the username "john35" on my site FOR THE FIRST TIME.

john35's data is shown to me and an empty grid is shown to me because there is no data in the database. from this moment a personalized cron for john35 starts, which saves the number of followers every day

it's possible to do? and how?

Answer 1

I don't know how other used to do it, but I always use supervisor for these type of jobs. It's similar to the cron, but there are much more configuration options.

Anyway, example for installation(CentOS) and implementation with it:

---

Create a service file, and fill it with these lines:

[Unit]
Description=Process Monitoring and Control Daemon
After=rc-local.service nss-user-lookup.target

[Service]
Type=forking
ExecStart=/usr/bin/supervisord -c /etc/supervisord.conf

[Install]
WantedBy=multi-user.target

then enable the auto start:

sudo systemctl enable supervisord

and start the service:

sudo systemctl start supervisord

[Note] You have to start supervisord before you can access to supervisorctl.

sudo supervisord -c /etc/supervisord.conf
sudo supervisorctl -c /etc/supervisord.conf

After this point you can use it easily:

// Reload the daemon’s configuration files, without add/remove (no restarts)
sudo supervisorctl reread

// Reload config and add/remove as necessary, and will restart affected programs
sudo supervisorctl update


sudo supervisorctl <start/restart/stop> <workerIniFileName>:*

[Note] Ini file location: /etc/supervisor.d/

Example: random-worker.ini

[program:random-worker]
process_name=%(program_name)s_%(process_num)02d
command=<php/sh/py/command/ect script location> // example: php /var/www/html/project/asd.php
autostart=true
autorestart=true
user=apache // or any other user
numprocs=4 // number of process you would like to execute simultaneously
redirect_stderr=true
stdout_logfile=/var/log/<name of the logfile>.log

The script implementation is totally up to you. Example in php:

public function onShutdown()
{
    $this->info('Shutdown called, exiting.');
}

public function onSignal($signo)
{
    $this->info("Received PCNTL signal {$signo}");
    die();
}

public function actionRunWorker($priorityLevel = false)
{
    set_time_limit(0);
    declare(ticks=1);

    register_shutdown_function([$this, 'onShutdown']);
    pcntl_signal(SIGTERM, [$this, 'onSignal']);
    pcntl_signal(SIGHUP, [$this, 'onSignal']);
    pcntl_signal(SIGINT, [$this, 'onSignal']);

    sleep(self::WORKER_SLEEP_TIME);
    while (1) {
        // Your code comes here
        sleep(self::WORKER_SLEEP_TIME);
    }
}