From d91e95ba62eb2e7f96571b6b9ec0c7e58148a0a0 Mon Sep 17 00:00:00 2001
From: Erich Eckner <git@eckner.net>
Date: Thu, 6 Dec 2018 09:50:11 +0100
Subject: lib/mysql.php: log queries and their duration

---
 lib/mysql.php | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/lib/mysql.php b/lib/mysql.php
index ec0a1ba..cd21eaa 100644
--- a/lib/mysql.php
+++ b/lib/mysql.php
@@ -13,17 +13,43 @@ if ( $mysql -> connect_error ) {
   die_500( "Connection failed: " . $mysql -> connect_error );
 }
 
+function print_important_trace_components($call) {
+  return substr($call['file'], strlen(BASE)+1) . '(' . $call['line'] . ')';
+}
+
+function mysql_log_duration_and_trace($start) {
+  $start = round((microtime(true) - $start) * 1000000);
+  $trace = debug_backtrace();
+  array_shift($trace);
+  // silently fail if logfile is unavailable
+  if (($fp = fopen(BASE . '/log', 'a')) !== false) {
+    flock($fp, LOCK_EX);
+    fwrite($fp,
+      date('Y-m-d H:i:s') . " " .
+      $start . " " .
+      implode(' ', array_map('print_important_trace_components', $trace)) . " - " .
+      $trace[0]['args'][0] . "\n"
+    );
+    flock($fp, LOCK_UN);
+    fclose($fp);
+  }
+}
+
 function mysql_run_query($query) {
   global $mysql;
+  $start = microtime(true);
   if ( ! $result = $mysql -> query($query) )
     die_500( "Query failed: " .  $mysql -> error );
+  mysql_log_duration_and_trace($start);
   return $result;
 }
 
 function mysql_prepare_query($query) {
   global $mysql;
+  $start = microtime(true);
   if ( ! $result = $mysql -> prepare($query) )
     die_500( "Prepare failed: " . $mysql -> error );
+  mysql_log_duration_and_trace($start);
   return $result;
 }
 
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