Monitoring: make use of Buffer while serving JSON

refs #13623

library/Icinga/File/Json.php

@@ -0,0 +1,129 @@
+<?php
+/* Icinga Web 2 | (c) 2016 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\File;
+
+use Icinga\Exception\IcingaException;
+use Icinga\Util\Buffer;
+use stdClass;
+use Traversable;
+
+/**
+ * Generates JSON from a query result
+ */
+class Json
+{
+    /**
+     * The query to generate JSON from the result of
+     *
+     * @var Traversable
+     */
+    protected $query;
+
+    /**
+     * Cache for {@link render()}
+     *
+     * @var Buffer|null
+     */
+    protected $renderBuffer;
+
+    /**
+     * Json constructor
+     *
+     * @param   Traversable $query  The query to generate JSON from the result of
+     */
+    protected function __construct(Traversable $query)
+    {
+        $this->query = $query;
+    }
+
+    /**
+     * Factory
+     *
+     * @param   Traversable $query  The query to generate JSON from the result of
+     *
+     * @return  static
+     */
+    public static function create(Traversable $query)
+    {
+        return new static($query);
+    }
+
+    /**
+     * Render JSON and pass it to the user agent (as with {@link fpassthru()})
+     */
+    public function dump()
+    {
+        $this->render()->fpassthru();
+    }
+
+    /**
+     * Return the rendered JSON
+     *
+     * @return string
+     */
+    public function __toString()
+    {
+        return (string) $this->render();
+    }
+
+    /**
+     * Return the rendered JSON
+     *
+     * @return Buffer
+     */
+    protected function render()
+    {
+        if ($this->renderBuffer === null) {
+            $this->renderBuffer = new Buffer();
+            $this->renderBuffer->append('[');
+
+            $first = true;
+            foreach ($this->query as $row) {
+                if ($first) {
+                    $first = false;
+                } else {
+                    $this->renderBuffer->append(',');
+                }
+                $this->renderBuffer->append($this->renderRow($row));
+            }
+
+            $this->renderBuffer->append(']');
+        }
+
+        return $this->renderBuffer;
+    }
+
+    /**
+     * Return a JSON string representing the given columns of a single row
+     *
+     * @param   stdClass    $columns
+     *
+     * @return  string
+     *
+     * @throws  IcingaException     In case of an error
+     */
+    protected function renderRow(stdClass $columns)
+    {
+        $result = json_encode($columns);
+        if ($result === false) {
+            if (function_exists('json_last_error_msg')) {
+                // since PHP 5.5
+                $errorMessage = json_last_error_msg();
+            } else {
+                $lastError = json_last_error();
+                $constants = get_defined_constants(true);
+                $errorMessage = 'Unknown error';
+                foreach ($constants['json'] as $constant => $value) {
+                    if ($value === $lastError && substr($constant, 0, 11) === 'JSON_ERROR_') {
+                        $errorMessage = $constant;
+                        break;
+                    }
+                }
+            }
+
+            throw new IcingaException('Couldn\'t encode %s as JSON: %s', print_r($columns, true), $errorMessage);
+        }
+        return $result;
+    }
+}

modules/monitoring/library/Monitoring/Controller.php

@@ -8,7 +8,7 @@ use Icinga\Exception\QueryException;
 use Icinga\Data\Filter\Filter;
 use Icinga\Data\Filterable;
 use Icinga\File\Csv;
-use Icinga\Util\Json;
+use Icinga\File\Json;
 use Icinga\Web\Controller as IcingaWebController;
 use Icinga\Web\Url;
 
@@ -60,8 +60,13 @@ class Controller extends IcingaWebController
                         'Content-Disposition',
                         'inline; filename=' . $this->getRequest()->getActionName() . '.json'
                     )
-                    ->appendBody(Json::encode($query->fetchAll()))
-                    ->sendResponse();
+                    ->sendHeaders();
+
+                while (ob_get_level()) {
+                    ob_end_clean();
+                }
+                Json::create($query)->dump();
+
                 exit;
             case 'csv':
                 $response = $this->getResponse();