New Daemon node to call and monitor long running external commands

utility/daemon/daemon.js

@@ -0,0 +1,106 @@
+/**
+ * Copyright 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.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+
+module.exports = function(RED) {
+    "use strict";
+    var spawn = require('child_process').spawn;
+
+    function DaemonNode(n) {
+        RED.nodes.createNode(this,n);
+        this.cmd = n.command;
+        this.args = n.args.split(" ") || [];
+        this.cr = n.cr;
+        this.op = n.op;
+        this.redo = n.redo;
+        this.running = false;
+        var node = this;
+
+        function inputlistener(msg) {
+            if (msg != null) {
+                if (!Buffer.isBuffer(msg.payload)) {
+                    if (typeof msg.payload === "object") { msg.payload = JSON.stringify(msg.payload); }
+                    if (typeof msg.payload !== "string") { msg.payload = msg.payload.toString(); }
+                    if (node.cr === true) { msg.payload += "\n"; }
+                }
+                if (RED.settings.verbose) { node.log("inp: "+msg.payload); }
+                if (node.child !== null) { node.child.stdin.write(msg.payload); }
+                else { node.warn("Command not running"); }
+            }
+        }
+
+        function runit() {
+            node.child = spawn(node.cmd, node.args);
+            if (RED.settings.verbose) { node.log(node.cmd+" "+JSON.stringify(node.args)); }
+            node.status({fill:"green",shape:"dot",text:"running"});
+            node.running = true;
+
+            node.on("input", inputlistener);
+
+            node.child.stdout.on('data', function (data) {
+                if (node.op == "string") { data = data.toString(); }
+                if (node.op == "number") { data = Number(data); }
+                if (RED.settings.verbose) { node.log("out: "+data); }
+                if (data && data.trim() !== "") {
+                    var msg = {payload:data};
+                    node.send([msg,null,null]);
+                }
+            });
+
+            node.child.stderr.on('data', function (data) {
+                if (node.op == "string") { data = data.toString(); }
+                if (node.op == "number") { data = Number(data); }
+                if (RED.settings.verbose) { node.log("err: "+data); }
+                var msg = {payload:data};
+                node.send([null,msg,null]);
+            });
+
+            node.child.on('close', function (code) {
+                if (RED.settings.verbose) { node.log("ret: "+code); }
+                var msg = {payload:code};
+                node.send([null,null,msg]);
+                node.child = null;
+                node.running = false;
+                node.status({fill:"red",shape:"ring",text:"stopped"});
+            });
+
+            node.child.on('error', function (err) {
+                if (err.errno === "ENOENT") { node.warn('Command not found'); }
+                else if (err.errno === "EACCES") { node.warn('Command not executable'); }
+                else { node.log('error: ' + err); }
+                node.status({fill:"grey",shape:"dot",text:"error"});
+            });
+        }
+
+        if (node.redo === true) {
+            var loop = setInterval( function() {
+                if (!node.running) {
+                    node.removeListener('input', inputlistener);
+                    node.warn("Restarting : " + node.cmd);
+                    runit();
+                }
+            }, 10000);  // Restart after 10 secs if required
+        }
+
+        node.on("close", function() {
+            if (node.child != null) { node.child.kill('SIGKILL'); }
+            if (RED.settings.verbose) { node.log(node.cmd+" stopped"); }
+            clearInterval(loop);
+        });
+
+        runit();
+    }
+    RED.nodes.registerType("daemon",DaemonNode);
+}