Truncate messages if they reach the max length of GELF messages, fixes #751

Author: Seldaek

src/Monolog/Formatter/GelfMessageFormatter.php

@@ -22,6 +22,8 @@
  */
 class GelfMessageFormatter extends NormalizerFormatter
 {
+    const MAX_LENGTH = 32766;
+
     /**
      * @var string the name of the system for the Gelf log message
      */
@@ -79,24 +81,48 @@ public function format(array $record)
             ->setHost($this->systemName)
             ->setLevel($this->logLevels[$record['level']]);
 
+        // start count with message length + system name length + 200 for padding / metadata
+        $len = 200 + strlen((string) $record['message']) + strlen($this->systemName);
+
+        if ($len > self::MAX_LENGTH) {
+            $message->setShortMessage(substr($record['message'], 0, self::MAX_LENGTH - 200));
+
+            return $message;
+        }
+
         if (isset($record['channel'])) {
             $message->setFacility($record['channel']);
+            $len += strlen($record['channel']);
         }
         if (isset($record['extra']['line'])) {
             $message->setLine($record['extra']['line']);
+            $len += 10;
             unset($record['extra']['line']);
         }
         if (isset($record['extra']['file'])) {
             $message->setFile($record['extra']['file']);
+            $len += strlen($record['extra']['file']);
             unset($record['extra']['file']);
         }
 
         foreach ($record['extra'] as $key => $val) {
-            $message->setAdditional($this->extraPrefix . $key, is_scalar($val) ? $val : $this->toJson($val));
+            $val = is_scalar($val) ? $val : $this->toJson($val);
+            $len += strlen($this->extraPrefix . $key . $val);
+            if ($len > self::MAX_LENGTH) {
+                $message->setAdditional($this->extraPrefix . $key, substr($val, 0, self::MAX_LENGTH - $len));
+                break;
+            }
+            $message->setAdditional($this->extraPrefix . $key, $val);
         }
 
         foreach ($record['context'] as $key => $val) {
-            $message->setAdditional($this->contextPrefix . $key, is_scalar($val) ? $val : $this->toJson($val));
+            $val = is_scalar($val) ? $val : $this->toJson($val);
+            $len += strlen($this->contextPrefix . $key . $val);
+            if ($len > self::MAX_LENGTH) {
+                $message->setAdditional($this->contextPrefix . $key, substr($val, 0, self::MAX_LENGTH - $len));
+                break;
+            }
+            $message->setAdditional($this->contextPrefix . $key, $val);
         }
 
         if (null === $message->getFile() && isset($record['context']['exception']['file'])) {

tests/Monolog/Formatter/GelfMessageFormatterTest.php

@@ -197,6 +197,24 @@ public function testFormatWithExtra()
         $this->assertEquals('pair', $message_array['_EXTkey']);
     }
 
+    public function testFormatWithLargeData()
+    {
+        $formatter = new GelfMessageFormatter();
+        $record = array(
+            'level' => Logger::ERROR,
+            'level_name' => 'ERROR',
+            'channel' => 'meh',
+            'context' => array('exception' => str_repeat(' ', 32767)),
+            'datetime' => new \DateTime("@0"),
+            'extra' => array('key' => str_repeat(' ', 32767)),
+            'message' => 'log'
+        );
+        $message = $formatter->format($record);
+        $messageArray = $message->toArray();
+        $this->assertLessThanOrEqual(32766, strlen($messageArray['_key']));
+        $this->assertLessThanOrEqual(32766, strlen($messageArray['_ctxt_exception']));
+    }
+
     private function isLegacy()
     {
         return interface_exists('\Gelf\IMessagePublisher');