New Daemon node to call and monitor long running external commands

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Dave C-J 2014-12-24 21:51:17 +00:00
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node-red-node-daemon
====================
A <a href="http://nodered.org" target="_new">Node-RED</a> node that runs and monitors a long running system command.
Similar to the **exec** node - but this calls the command at start time and then pipes any input to the node to the STDIN of the running command, and feeds any STDOUT to the first output.
Useful for monitoring command line based processes.
Install
-------
Run the following command in the root directory of your Node-RED install
npm install node-red-node-daemon
Usage
-----
Calls out to a long running system command. Sends <b>msg.payload</b> to stdin of the process.
Provides 3 outputs... stdout, stderr, and return code, from the running command.
If the called program stops (i.e. a return code is produced), this node can attempt to restart the command.
**Note :** when you stop Node-RED running we may not get a chance to kill the called program so it may remain running. You <i>may</i> have to kill it manually.
For example I have used it to run and then monitor the <a href="https://github.com/antirez/dump1090" target ="_new">dump1090</a> plane spotter, and also to interact with various python apps that everyone seem to write these days :-)

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<!--
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.
-->
<script type="text/x-red" data-template-name="daemon">
<div class="form-row">
<label for="node-input-command"><i class="fa fa-file"></i> Command</label>
<input type="text" id="node-input-command" placeholder="command">
</div>
<div class="form-row">
<label for="node-input-args"><i class="fa fa-list"></i> Args</label>
<input type="text" id="node-input-args" placeholder="space separated arguments">
</div>
<div class="form-row">
<label>&nbsp;</label>
<input type="checkbox" id="node-input-cr" style="display: inline-block; width: auto; vertical-align: top;">
<label for="node-input-cr" style="width: 70%;">Add [enter] to every message ?</label>
</div>
<div class="form-row">
<label>&nbsp;</label>
<input type="checkbox" id="node-input-redo" style="display: inline-block; width: auto; vertical-align: top;">
<label for="node-input-redo" style="width: 70%;">Relaunch command on exit or error ?</label>
</div>
<div class="form-row">
<label for="node-input-op"> and</label>
<select id="node-input-op" style='width:70%'>
<option value="string">format reply as a string</option>
<option value="buffer">leave reply as a buffer</option>
<option value="number">try to convert reply to a number</option>
</select>
</div>
<div class="form-row">
<label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
<input type="text" id="node-input-name" placeholder="Name">
</div>
</script>
<script type="text/x-red" data-help-name="daemon">
<p>Calls out to a long running system command. Sends <b>msg.payload</b> to stdin of the process.</p>
<p>Provides 3 outputs... stdout, stderr, and return code , from the running command.</p>
<p>If the called program stops (i.e. a return code is produced), this node can attempt to restart the command.</p>
<p><b>Note :</b> when you stop Node-RED running we may not get a chance to kill the called program so it may remain running. You <i>may</i> have to kill it manually.</p>
</script>
<script type="text/javascript">
RED.nodes.registerType('daemon',{
category: 'advanced-function',
color:"darksalmon",
defaults: {
command: {value:"",required:true},
args: {value:""},
cr: {value:false},
redo: {value:true},
op: {value:"string"},
name: {value:""}
},
inputs:1,
outputs:3,
icon: "arrow-in.png",
align: "right",
label: function() {
return this.name||this.command;
},
labelStyle: function() {
return this.name?"node_label_italic":"";
}
});
</script>

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/**
* 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);
}

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{
"name" : "node-red-node-daemon",
"version" : "0.0.1",
"description" : "A Node-RED node that runs and monitors a long running system command.",
"dependencies" : {
},
"repository" : {
"type":"git",
"url":"https://github.com/node-red/node-red-nodes/tree/master/utility/daemon"
},
"license": "Apache-v2.0",
"keywords": [ "node-red", "daemon", "shell", "exec" ],
"node-red" : {
"nodes" : {
"daemon": "daemon.js"
}
},
"author": {
"name": "Dave Conway-Jones",
"email": "ceejay@vnet.ibm.com",
"url": "http://nodered.org"
}
}