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Cron Design: Running Cron

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MPG UniCenter

MPG UniCenter

Contents

Uniform Server Portable Cron Design

Both Cron start and stop requests are passed to a central control block for processing. This control block consists of two scripts start_servers.php and stop_servers.php these are located in folder UniServer\unicon\main. Further processing if required is handed on to the appropriate script or scripts.

In terms of interfacing having a central control architecture provides consistency and reduces complexity. This page covers the Cron interface and control processing.

Binary coding

Programs or batch files that run either of the control scripts start_servers.php or stop_servers.php must include a single binary coded parameter. If this parameter is missing defaults are used. A parameter overrides any default settings this allows independent control of a particular function.

Currenty the following binary codes have been assigned:


             CODE  Options are binary coded as follows:
                   Bit function
Apache         1   1 - Run Apache server 0 - ignore
Mysql          2   1 - Run MySQL  server 0 - ignore
Index page     4   1 - Start Index page  0 - ignore
MySQL Console  8   1 - Display console   0 - ignore
Cron          16   1 - Run cron          0 - ignore

Binary bit coding does not conform to the classic definition where 1 means on and 0 means off. Uniform Server uses 1 to mean perform the function while 0 means ignore and do nothing.

Having two separate files start_servers.php and stop_servers.php respectively performs the on-off functionality.

Defaults are set in file UniServer\unicon\main\includes\config.inc.php by the following lines:

  • $server_standard = 7;
  • $server_service = 7;

What does this techno babble mean!

Well if you run start_servers.php with no parameter it picks up the default from variable $server_standard which has a value of binary code 7.

Splitting code 7 into its individual components gives 1+2+4 hence start_servers.php runs the following processes:

  • 1 Apache
  • 2 Mysql
  • 4 Index page

Similarly running stop_servers.php with no parameter will stop the above running processes.

Using binary coding offers single bit (process) control this is exploited when running Cron explained below.

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Running portable Cron

With an understanding of the above we can look at running Cron in more detail.

Manually

Portable Cron is run from one of two locations.

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


Start_Cron.bat contains the following line:

..\usr\local\php\php.exe -n  ..\unicon\main\start_servers.php 16
  • ..\usr\local\php\php.exe -n Runs the PHP interpreter (php.exe) with no (-n) configuration file and runs the following file:
  • ..\unicon\main\start_servers.php 16 Script start_servers.php is run with parameter 16 (Runs only Cron)


Stop_Cron.bat contains the following line:

..\usr\local\php\php.exe -n  ..\unicon\main\stop_servers.php 16
  • ..\usr\local\php\php.exe -n Runs the PHP interpreter (php.exe) with no (-n) configuration file and runs the following file:
  • ..\unicon\main\stop_servers.php 16 Script stop_servers.php is run with parameter 16 (Stops only Cron)


UniTray

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

Have a peek inside Unitrays configuration file: UniServer\unicon\tray_menu\UniTray1.ini

These two lines (split on purpose to prevent breaking the Wiki) control Cron start and stop. Only thing worth of note is they use binary code 16

Type: item; Caption: "Start Portable Cron"; Action: shellexecute; FileName:
"%PHP%\php-win.exe"; Parameters: " -n %ServerConMain%\start_servers.php 16"; Glyph: 9


Type: item; Caption: "Stop  Portable Cron"; Action: shellexecute; FileName:
"%PHP%\php-win.exe"; Parameters: " -n %ServerConMain%\stop_servers.php 16"; Glyph: 11

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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

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Cron Start Stop

The control block consists of two scripts start_servers.php and stop_servers.php these are located in folder UniServer\unicon\main.

When these scripts are run they process a parameter passed in the case of Cron they are looking for binary code 16.

The appropriate sections are reproduce below along with a description of salient points.

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start_servers.php - Cron Section

  • $server_operation contains either the parameter passed or default this is compared with binary 16 using the “binary & bit operator” On a match runs the block of code.
  • If Apache not running give up
  • If Cron already running again give up
  • Cron tracker is used to break out of an infinite while loop (covered later)
  • Cron requires further process hence is handed over to a detached process.
  • The cmd is built. uniserv.exe is used to hide this detached process.
  • pclose(popen($cmd,'r')) runs script run_cron.php as a detached hidden process

Note 1: For testing the command can be switch making the process visible.

Note 2: If a user turns PC off without closing the servers next time servers are run a clean up operation is performed. Hence this code is run set_cron_tracker("stop") see RUN APACHE SERVER section

 

start_servers.php

// === RUN CRON ============================================================
if ((int)$server_operation & 16 ){    // Cron enabled by config or parameter  

 if(apache_running()){                // Only run cron if Apache running
                                      // otherwise ignore and exit quietly

   if(get_cron_tracker() == "run"){   // Cron already running
     print " Cron already running\n"; // Already running, give up
   }
   else{                              // not running
     set_cron_tracker("run");         // set tracker to run
     print " Cron started \n";        // inform user

    // Test switch between the two: visibe
    //$cmd = 'start ..\..\usr\local\php\php.exe run_cron.php'; // Test

    // Test switch between the two: hidden
    $cmd = 'start uniserv.exe "..\..\usr\local\php\php.exe run_cron.php"';

    pclose(popen($cmd,'r'));             // Start detatched process 

   }
 }//End Apache running
}// End run cron

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stop_servers.php - Cron Section

  • $server_operation contains either the parameter passed or default this is compared with binary 16 using the “binary & bit operator” On a match runs the block of code.
  • If Cron is running set the tracker to "stop"

The cron script on detecting a tracker value of "stop" breaks out of an inifinatent while loop thus killing the process.

 

stop_servers.php


// === Stop Cron ========================================================

if ((int)$server_operation & 16 ){ // Cron enabled by config or parameter
 if(get_cron_tracker() == "stop"){ // Already stopped or not running
  print " Cron not running\n";
 }
 else{
  set_cron_tracker("stop");        // Is running signal to stop
  print" Cron stopped.\n";         // Inform user
 }
}

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Summary

The above has explained how Cron integrates into Uniforms Servers control architecture and the selective nature of binary coding.

A request to run Cron results in running a new detached process. Although a single script I have split it over a number of pages to explain each section in detail.

Next page covers the fundamental building block, an infinite while loop.

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