randomize minutes for clublog jobs

application/config/migration.php

@@ -22,7 +22,7 @@ $config['migration_enabled'] = TRUE;
 |
 */
 
-$config['migration_version'] = 258;
+$config['migration_version'] = 259;
 
 /*
 |--------------------------------------------------------------------------

application/migrations/259_randomize.php

@@ -0,0 +1,53 @@
+<?php
+
+defined('BASEPATH') or exit('No direct script access allowed');
+class Migration_randomize extends CI_Migration {
+
+	/**
+	 * We randomize the minute for clublog cronjobs to reduce the load on clublog servers
+	 * We only apply this change if the cronjob expression is still set to the default value
+	 */
+
+	public function up() {
+		/**
+		 * Reference:
+		 *   - clublog_upload was added in mig 196
+		 *   - clublog_download was added in mig 197
+		 */
+		$cron_jobs = [
+			'clublog_download' => '7 00 * * *',
+			'clublog_upload' => '3 */6 * * *',
+		];
+
+		foreach ($cron_jobs as $id => $default_expression) {
+			$query = $this->db->query("SELECT expression FROM cron WHERE id=?", [$id]);
+			$row = $query->row();
+			if ($row && $row->expression === $default_expression) {
+				
+				$random_minute = mt_rand(0, 59);
+				
+				$parts = explode(' ', $default_expression);
+				$parts[0] = (string)$random_minute;
+				$new_expression = implode(' ', $parts);
+
+				// all expressions should have the same format
+				$new_expression = str_replace(' 00 ', ' 0 ', $new_expression);
+				
+				$this->dbtry("UPDATE cron SET expression='" . $new_expression . "' WHERE id='" . $id . "'");
+			}
+		}
+
+	}
+
+	public function down() {
+		// no way back necessary
+	}
+
+	function dbtry($what) {
+		try {
+			$this->db->query($what);
+		} catch (Exception $e) {
+			log_message("error", "Something gone wrong while altering a table: ".$e." // Executing: ".$this->db->last_query());
+		}
+	}
+}