Add DeduplicationHandler to avoid spamming the same log records over and over

src/Monolog/Handler/DeduplicationHandler.php

@@ -0,0 +1,169 @@
+<?php
+
+/*
+ * This file is part of the Monolog package.
+ *
+ * (c) Jordi Boggiano <j.boggiano@seld.be>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Monolog\Handler;
+
+use Monolog\Logger;
+
+/**
+ * Simple handler wrapper that deduplicates log records across multiple requests
+ *
+ * It also includes the BufferHandler functionality and will buffer
+ * all messages until the end of the request or flush() is called.
+ *
+ * This works by storing all log records' messages above $deduplicationLevel
+ * to the file specified by $deduplicationStore. When further logs come in at the end of the
+ * request (or when flush() is called), all those above $deduplicationLevel are checked
+ * against the existing stored logs. If they match and the timestamps in the stored log is
+ * not older than $time seconds, the new log record is discarded. If no log record is new, the
+ * whole data set is discarded.
+ *
+ * This is mainly useful in combination with Mail handlers or things like Slack or HipChat handlers
+ * that send messages to people, to avoid spamming with the same message over and over in case of
+ * a major component failure like a database server being down which makes all requests fail in the
+ * same way.
+ *
+ * @author Jordi Boggiano <j.boggiano@seld.be>
+ */
+class DeduplicationHandler extends BufferHandler
+{
+    /**
+     * @var string
+     */
+    protected $deduplicationStore;
+
+    /**
+     * @var int
+     */
+    protected $deduplicationLevel;
+
+    /**
+     * @var int
+     */
+    protected $time;
+
+    /**
+     * @var bool
+     */
+    private $gc = false;
+
+    /**
+     * @param HandlerInterface $handler            Handler.
+     * @param string           $deduplicationStore The file/path where the deduplication log should be kept
+     * @param int              $deduplicationLevel The minimum logging level for log records to be looked at for deduplication purposes
+     * @param int              $time               The period (in seconds) during which duplicate entries should be suppressed after a given log is sent through
+     * @param Boolean          $bubble             Whether the messages that are handled can bubble up the stack or not
+     */
+    public function __construct(HandlerInterface $handler, $deduplicationStore = null, $deduplicationLevel = Logger::ERROR, $time = 60, $bubble = true)
+    {
+        parent::__construct($handler, 0, Logger::DEBUG, $bubble, false);
+
+        $this->deduplicationStore = $deduplicationStore === null ? sys_get_temp_dir() . '/monolog-dedup-' . substr(md5(__FILE__), 0, 20) .'.log' : $deduplicationStore;
+        $this->deduplicationLevel = $deduplicationLevel;
+        $this->time = $time;
+    }
+
+    public function flush()
+    {
+        if ($this->bufferSize === 0) {
+            return;
+        }
+
+        $passthru = null;
+
+        foreach ($this->buffer as $record) {
+            if ($record['level'] >= $this->deduplicationLevel) {
+
+                $passthru = $passthru || !$this->isDuplicate($record);
+                if ($passthru) {
+                    $this->appendRecord($record);
+                }
+            }
+        }
+
+        // default of null is valid as well as if no record matches duplicationLevel we just pass through
+        if ($passthru === true || $passthru === null) {
+            $this->handler->handleBatch($this->buffer);
+        }
+
+        $this->clear();
+
+        if ($this->gc) {
+            $this->collectLogs();
+        }
+    }
+
+    private function isDuplicate(array $record)
+    {
+        if (!file_exists($this->deduplicationStore)) {
+            return false;
+        }
+
+        $store = file($this->deduplicationStore, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
+        if (!is_array($store)) {
+            return false;
+        }
+
+        $yesterday = time() - 86400;
+        $timestampValidity = $record['datetime']->getTimestamp() - $this->time;
+        $line = $record['level_name'] . ':' . $record['message'];
+
+        for ($i = count($store) - 1; $i >= 0; $i--) {
+            list($timestamp, $level, $message) = explode(':', $store[$i]);
+
+            if ($level === $record['level_name'] && $message === $record['message'] && $timestamp > $timestampValidity) {
+                return true;
+            }
+
+            if ($timestamp < $yesterday) {
+                $this->gc = true;
+            }
+        }
+
+        return false;
+    }
+
+    private function collectLogs()
+    {
+        if (!file_exists($this->deduplicationStore)) {
+            return false;
+        }
+
+        $handle = fopen($this->deduplicationStore, 'rw+');
+        flock($handle, LOCK_EX);
+        $validLogs = array();
+
+        $timestampValidity = time() - $this->time;
+
+        while (!feof($handle)) {
+            $log = fgets($handle);
+            if (substr($log, 0, 10) >= $timestampValidity) {
+                $validLogs[] = $log;
+            }
+        }
+
+        ftruncate($handle, 0);
+        rewind($handle);
+        foreach ($validLogs as $log) {
+            fwrite($handle, $log);
+        }
+
+        flock($handle, LOCK_UN);
+        fclose($handle);
+
+        $this->gc = false;
+    }
+
+    private function appendRecord(array $record)
+    {
+        file_put_contents($this->deduplicationStore, $record['datetime']->getTimestamp() . ':' . $record['level_name'] . ':' . $record['message'] . "\n", FILE_APPEND);
+    }
+}