Merge pull request #286 from pi-hole/new/taillog

Add non-blocking tailing of pihole.log

api.php

@@ -80,6 +80,10 @@
         $data = array_merge($data, getGravity());
     }
 
+    if (isset($_GET['tailLog'])) {
+        $data = array_merge($data, tailPiholeLog($_GET['tailLog']));
+    }
+
     function filterArray(&$inArray) {
 	    $outArray = array();
 	    foreach ($inArray as $key=>$value) {

data.php

@@ -293,6 +293,33 @@
         return $allQueries;
     }
 
+    function tailPiholeLog($param) {
+        // Not using SplFileObject here, since direct
+        // usage of f-streams will be much faster for
+        // files as large as the pihole.log
+        global $logListName;
+        $file = fopen($logListName,"r");
+        $offset = intval($param);
+        if($offset > 0)
+        {
+            // Seeks on the file pointer where we want to continue reading is known
+            fseek($file, $offset);
+            $lines = [];
+            while (!feof($file)) {
+                array_push($lines,fgets($file));
+            }
+            return ["offset" => ftell($file), "lines" => $lines];
+        }
+        else
+        {
+            // Locate the current position of the file read/write pointer
+            fseek($file, -1, SEEK_END);
+            // Add one to skip the very last "\n" in the log file
+            return ["offset" => ftell($file)+1];
+        }
+        fclose($file);
+    }
+
     /******** Private Members ********/
     function gravityCount() {
         global $gravityListName,$blackListFile;

header.php

@@ -353,6 +353,12 @@
                         <i class="fa fa-search"></i> <span>Query adlists</span>
                     </a>
                 </li>
+                <!-- Tail pihole.log -->
+                <li>
+                    <a href="taillog.php">
+                        <i class="fa fa-list-ul"></i> <span>Tail pihole.log</span>
+                    </a>
+                </li>
                 <!-- Toggle -->
                 <?php
                 if ($pistatus == "1") {

js/pihole/taillog.js

@@ -0,0 +1,40 @@
+var offset, timer, pre, scrolling = true;
+
+// Check every 200msec for fresh data
+var interval = 200;
+
+// Function that asks the API for new data
+function reloadData(){
+    clearTimeout(timer);
+    $.getJSON("api.php?tailLog="+offset, function (data)
+    {
+        offset = data["offset"];
+        pre.append(data["lines"]);
+    });
+
+    if(scrolling)
+    {
+        window.scrollTo(0,document.body.scrollHeight);
+    }
+    timer = setTimeout(reloadData, interval);
+}
+
+$(function(){
+    // Get offset at first loading of page
+    $.getJSON("api.php?tailLog", function (data)
+    {
+        offset = data["offset"];
+    });
+    pre = $("#output");
+    // Trigger function that looks for new data
+    reloadData();
+});
+
+$("#chk1").click(function() {
+    $("#chk2").prop("checked",this.checked);
+    scrolling = this.checked;
+});
+$("#chk2").click(function() {
+    $("#chk1").prop("checked",this.checked);
+    scrolling = this.checked;
+});

taillog.php

@@ -0,0 +1,18 @@
+<?php
+    require "header.php";
+?>
+<!-- Title -->
+<div class="page-header">
+    <h1>Output the last lines of the pihole.log file (live)</h1>
+</div>
+
+<div class="checkbox"><label><input type="checkbox" name="active" checked id="chk1"> Automatic scrolling on update</label></div>
+<pre id="output" style="width: 100%; height: 100%;"></pre>
+<div class="checkbox"><label><input type="checkbox" name="active" checked id="chk2"> Automatic scrolling on update</label></div>
+
+<?php
+    require "footer.php";
+?>
+
+
+<script src="js/pihole/taillog.js"></script>