IcingaObject: Render flapping thresholds downwards compatible

Settings are ignored in Icinga < 2.8.0 and a warning is logged.

refs #330

library/Director/IcingaConfig/IcingaConfig.php

@@ -516,6 +516,7 @@ class IcingaConfig
             )
         )->prepend(
             "\nconst DirectorStageDir = dirname(dirname(current_filename))\n"
+            . $this->renderFlappingLogHelper()
             . $this->renderHostOverridableVars()
             . $this->renderMagicApplyFor()
         );
@@ -523,6 +524,19 @@ class IcingaConfig
         return $this;
     }
 
+    protected function renderFlappingLogHelper()
+    {
+        return '
+globals.directorWarnedOnceForThresholds = false;
+globals.directorWarnOnceForThresholds = function() {
+    if (globals.directorWarnedOnceForThresholds == false) {
+        globals.directorWarnedOnceForThresholds = true
+        log(LogWarning, "config", "Director: flapping_threshold_high/low is not supported in this Icinga 2 version!")
+    }
+}
+';
+    }
+
     protected function renderHostOverridableVars()
     {
         $settings = $this->connection->settings();

library/Director/Objects/IcingaObject.php

@@ -1664,6 +1664,26 @@ abstract class IcingaObject extends DbObject implements IcingaConfigRenderer
     /**
      * @codingStandardsIgnoreStart
      */
+    protected function renderFlapping_threshold_high()
+    {
+        return $this->renderFlappingThreshold('flapping_threshold_high');
+    }
+
+    protected function renderFlapping_threshold_low()
+    {
+        return $this->renderFlappingThreshold('flapping_threshold_low');
+    }
+
+    protected function renderFlappingThreshold($key)
+    {
+        return sprintf(
+            "    try { // This setting is only available in Icinga >= 2.8.0\n"
+            . "    %s"
+            . "    } except { globals.directorWarnOnceForThresholds() }\n",
+            c::renderKeyValue($this->numericProperties[$key], c::renderFloat($this->$key))
+        );
+    }
+
     protected function renderLegacyHost_id()
     {
         return $this->renderLegacyRelationProperty(