Cron Design: Introduction

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MPG UniCenter

MPG UniCenter

Uniform Server Portable Cron Design

Portable Cron was integrated into Uniform Server 5-Nano. Although useful, it suffered from a number of limitations. A new design has addressed these issues and offers more flexibility.

That said, you may find it does not meet your particular requirements. The best solution is to design new scripts or modify the existing ones.

The following provides a detailed description of the current implementation, which you can use as a basis for new designs or tweak the existing scripts.

Background

Before looking at configuration, this is quick overview what portable Cron is and what it is not.

Cron

Cron originated from a Unix environment. It is a job scheduler that allows scripts to be run automatically at a certain time or date.

Cron (chronograph) has become a more general term referring to a periodic tick.

Portable Cron

Why portable Cron? For a permanent installation of UniServer running as a service, you can set up Windows to schedule a task similar to Unix Cron. Check out How To Schedule Tasks in Windows XP for details

This is not practical when running UniServer from a USB memory stick, which implies portability. It means you need to reconfigure each new machine. UniServer 5-Nano resolves this with a small script scheduler referred to as portable Cron.

It’s fully integrated into UniServers’s control architecture, allowing it to be run from either batch files or UniTray.

Configuration

To understand the design, it’s worth first looking at configuration. Knowing how to configure Cron also serves as a specification.

To run each individual script, a number of parameters are set in a configuration file: cron.ini. This file has a standard format making it very easy to set up and use.

Each script to be run is defined in a self-contained block. Each block starts with a unique header. Here's an example:

[moodle] 
start  = 2009-09-21 2:56:00
period = hourly
path   = http://localhost/moodle/admin/cron.php
ref =

Explanation

[moodle] - Header a unique name enclosed in square brackets.
start - Time you initially want the script to start (seconds are ignored)
period - How often the script is to be run after the initial start
path - Full path and name of the script to be run
ref - A tracker set by Cron script effectively time to next run. Deleting this value allows a new start time to be set (covered later)

Detail

[moodle]

 

Header uniquely names this block note no spaces allowed in name.

start

Initial start time when script is to be run it has the following format:
Y-M-D H:M:S - Note: A 24 hour clock is used, seconds are ignored hence set to 00

period

=

How often to run script from the above reference start time
Valid values are: hourly, daily, weekly, monthly
Fine control is offered by using a numeric specified in seconds

path

=

Two types of scripts are runnable with paths as follows:

  • For a web application full URL of the script e.g. http://localhost/drupal/cron.php
  • Local CLI scripts relative path and name e.g. ..\..\plugins\cron_test\dtdns_updater.php

ref

=

A time stamp updated by the Cron script. Initial value is set by a user value blank.

Note 1: Cron automatically updates ref with the initial start time set and
period. Every time a script is run, the value is updated with a new Cron reference.
This defines when the next run is to start.

Note 2: To specify a new start time first set a new value for start and
delete the ref number (if there is one), then save the file. The script will run at the
date and time set and thereafter at a period you defined.

General notes

Configuration file location: UniServer\unicon\main\cron.ini

Configuration file contains pre-configured CLI blocks dtdns and db_backup. Uncomment to enable either block (remove semicolons).

Paths

The configuration file also contains pre-configured Web blocks drupal and moodle. Again uncomment to enable a block.

Note 1: If these were installed to a different folder change the path accordingly.

Note 2: If you have moved the servers remember to add a port number to the URL.

For example moving the servers once, Apache port becomes 81 hence these two paths:

  • http://localhost/moodle/admin/cron.php
  • http://localhost/drupal/cron.php

Become:

  • http://localhost:81/moodle/admin/cron.php
  • http://localhost:81/drupal/cron.php


How to run portable Cron

Manually

Portable Cron is run from one of two locations.

UniTray:

  • Left or Right mouse click tray icon
  • To run Cron: Advanced > Start Portable Cron
  • To stop Cron: Advanced > Stop Portable Cron

Alternative Control:

  • Navigate to folder UniServer\alternative_control
  • To run Cron: Double click on Start_Cron.bat
  • To stop Cron: Double click on Stop_Cron.bat


Automatic

Cron can be configured to run automatically when the servers are started.

Edit file UniServer\unicon\tray_menu\UniTray1.ini

These four lines (lines three and four split on purpose to prevent breaking the Wiki) control Server Start and Stop.

Change binary code from 7 to 23 for lines three and four.

;=== LEFT MENU ============
[Menu.Left]

Type: item; Caption: "Start UniServer (Apache MySQL)"; Action: shellexecute; FileName:
 "%PHP%\php.exe"; Parameters: " -n %ServerConMain%\start_servers.php 7";ShowCmd: hidden; Glyph: 9

Type: item; Caption: "Stop  UniServer (Apache MySQL)"; Action: shellexecute; FileName:
 "%PHP%\php.exe"; Parameters: " -n %ServerConMain%\stop_servers.php 7";ShowCmd: hidden; Glyph: 11


Logging

Cron logs the fooling information:

  • Time Cron was started
  • Start time and path of a script that is run
  • Time Cron was stopped. Note if missing from log means servers were not shut down before tuning PC off

Cron logging is enabled by default this can be disabled by editing the following file:

UniServer\unicon\main\run_cron.php

  • Change line: $logging = true;
  • To: $logging = false;

Note: Name and location of log file is : UniServer\unicon\main\cron_log.txt

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Summary

Above is essentially a user interface and to a certain extent the design specification.

Remaining pages looks at design; first we take a more detailed look at running Cron.

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