Modify Tail node to only send new messages

Now with test that works with it.
Part of Issue #326
Now need to redo with libs that support windows.

nodes/core/storage/28-tail.html

@@ -16,7 +16,7 @@
 
 <script type="text/x-red" data-template-name="tail">
     <div class="form-row node-input-filename">
-         <label for="node-input-filename"><i class="icon-file"></i> Filename</label>
+         <label for="node-input-filename"><i class="fa fa-file"></i> Filename</label>
          <input type="text" id="node-input-filename" placeholder="Filename">
     </div>
     <div class="form-row">
@@ -25,15 +25,15 @@
         <label for="node-input-split" style="width: 70%;">Split lines if we see \n ?</label>
     </div>
     <div class="form-row">
-        <label for="node-input-name"><i class="icon-tag"></i> Name</label>
+        <label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
         <input type="text" id="node-input-name" placeholder="Name">
     </div>
-    <div class="form-tips">WON'T work on Windows.</div>
+    <!-- <div class="form-tips">WON'T work on Windows.</div> -->
 </script>
 
 <script type="text/x-red" data-help-name="tail">
     <p>Tails (watches for things to be added) to the configured file. (Linux/Mac ONLY)</p>
-    <p>This won't work on Windows filesystems (as it relies on the tail -F command) so we will probably have to hide it in future.</p>
+    <p>This won't work on Windows filesystems, as it relies on the tail -F command.</p>
 </script>
 
 <script type="text/javascript">

nodes/core/storage/28-tail.js

@@ -1,5 +1,5 @@
 /**
- * Copyright 2013 IBM Corp.
+ * Copyright 2013, 2014 IBM Corp.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,6 +18,11 @@ module.exports = function(RED) {
     "use strict";
     var fs = require("fs");
     var spawn = require('child_process').spawn;
+    var plat = require('os').platform();
+
+    if (plat.match(/^win/)) {
+        throw "Info : Currently not supported on Windows.";
+    }
 
     function TailNode(n) {
         RED.nodes.createNode(this,n);
@@ -28,7 +33,7 @@ module.exports = function(RED) {
 
         var err = "";
         // TODO: rewrite to use node-tail
-        var tail = spawn("tail", ["-F", this.filename]);
+        var tail = spawn("tail", ["-F", "-n", "0", this.filename]);
         tail.stdout.on("data", function (data) {
             if (node.split) {
                 // TODO: allow customisation of the line break - as we do elsewhere

test/nodes/core/storage/28-tail_spec.js

@@ -23,14 +23,17 @@ var tailNode = require("../../../../nodes/core/storage/28-tail.js");
 var helper = require("../../helper.js");
 
 describe('TailNode', function() {
-    
+
     var resourcesDir = path.join(__dirname,"..","..","..","resources");
     var fileToTail = path.join(resourcesDir,"28-tail-test-file.txt");
-    
+    fs.writeFile(fileToTail, "Tail message line 1\nTail message line 2\n", function (err) {
+        if (err) { console.log('cannot write to '+fileToTail); }
+    });
+
     beforeEach(function(done) {
         helper.startServer(done);
     });
-    
+
     afterEach(function(done) {
         helper.unload();
         helper.stopServer(done);
@@ -44,8 +47,8 @@ describe('TailNode', function() {
             done();
         });
     });
-    
+
-    it('should tail a file', function(done) {
+    it('tail should tail a file', function(done) {
         var flow = [{id:"tailNode1", type:"tail", name: "tailNode", "split":true, "filename":fileToTail, "wires":[["helperNode1"]]},
                     {id:"helperNode1", type:"helper", wires:[]}];
         helper.load(tailNode, flow, function() {
@@ -53,27 +56,57 @@ describe('TailNode', function() {
             var helperNode1 = helper.getNode("helperNode1");
             var inputCounter = 0;
             helperNode1.on("input", function(msg) {
-                console.log(msg);
+                //console.log(msg);
                 msg.should.have.property('topic', fileToTail);
-                msg.payload.should.equal("Tail message line" + (++inputCounter));
+                msg.payload.should.equal("Tail message line " + (++inputCounter + 2));
-                if(inputCounter === 2) {
+                if (inputCounter === 2) {
                     done();
                 }
             });
+            fs.appendFileSync(fileToTail, "Tail message line 3\nTail message line 4\n");
         });
     });
-    
+
-    it('work in non-split mode', function(done) {
+    it('tail should work in non-split mode', function(done) {
         var flow = [{id:"tailNode1", type:"tail", name: "tailNode", "split":false, "filename":fileToTail, "wires":[["helperNode1"]]},
                     {id:"helperNode1", type:"helper", wires:[]}];
         helper.load(tailNode, flow, function() {
             var tailNode1 = helper.getNode("tailNode1");
             var helperNode1 = helper.getNode("helperNode1");
             helperNode1.on("input", function(msg) {
+                //console.log(msg);
                 msg.should.have.property('topic', fileToTail);
-                msg.payload.should.equal("Tail message line1\nTail message line2\n");
+                msg.payload.should.equal("Tail message line 5\nTail message line 6\n");
                 done();
             });
+            fs.appendFile(fileToTail, "Tail message line 5\nTail message line 6\n");
         });
     });
+
+    it('tail should handle file going away and coming back', function(done) {
+        var flow = [{id:"tailNode1", type:"tail", name: "tailNode", "split":true, "filename":fileToTail, "wires":[["helperNode1"]]},
+                    {id:"helperNode1", type:"helper", wires:[]}];
+        helper.load(tailNode, flow, function() {
+            var tailNode1 = helper.getNode("tailNode1");
+            var helperNode1 = helper.getNode("helperNode1");
+            var inputCounter = 0;
+            var warned = false;
+            tailNode1.on("log", function(msg) {
+                if (msg.level == "warn") { warned = true; }
+                if ((inputCounter === 3)&&(warned === true)) { done(); }
+            });
+            helperNode1.on("input", function(msg) {
+                msg.should.have.property('topic', fileToTail);
+                msg.payload.should.equal("Tail message line A");
+                inputCounter += 1;
+                if ((inputCounter === 3)&&(warned === true)) { done(); }
+            });
+            fs.writeFileSync(fileToTail, "Tail message line A\n");
+            setTimeout( function() {
+                fs.appendFileSync(fileToTail, "Tail message line A\n");
+                fs.appendFileSync(fileToTail, "Tail message line A\n");
+            },250);
+        });
+    });
+
 });

test/resources/28-tail-test-file.txt

@@ -1,2 +1,3 @@
-Tail message line1
+Tail message line A
-Tail message line2
+Tail message line A
+Tail message line A