Close properly the openmct child process

- The previously returned 'ChildProcess' object was the 'npm' process.
- This only allowed killing the child process through CTRL+C input (that
  stdin string would then generate the SIGINT event which would then be
  propagated to the child processes
  npm start
     -> sh -c ". ${NVM_DIR}/nvm.sh; nvm use v14.17.0; node server.js"
         -> node server.js
- Sending a SIGQUIT, SIGTERM or SIGINT from terminal though 'kill -s...'
  to the 'npm start' process, parent of the node.js process wouldn't kill
  the later, and there was no direct way to retrieve the node.js process
  pid programmatically.
- We should retrieve the PID information directly from the child node.js
  process through an IPC channel between child and parent node.js processes.
- For this we add a 4rd stdio entry for the spawned command:
  'spawn(...,{..., stdio: ['pipe','pipe','pipe','ipc']})'.
- We send the node.js child process PID to the parent process via the created
  IPC channel.
- We have to spawn a 'sh runModule.sh' command instead of the 'npm start' as
  npm does not propagate the IPC channel either.
- The sh script 'runModule.sh' holds the same commands as the npm script used to.

Now both node.js processes can be killed through 'kill -s...' command or through
the 'CTRL+C' input.

iCubTelemVizServer/iCubTelemVizServer.js

@@ -180,7 +180,7 @@ console.log(ret.message);
 
 function handleTermination(signal) {
     console.log('Received '+signal+' ...');
-    openMctServerHandler.stop();
+    openMctServerHandler.stop(signal);
     const closeTelemServerPromise = new Promise(function(resolve,reject) {
         telemServer.close((error) => {
             if (error === undefined) {

iCubTelemVizServer/openMctServerHandler.js

@@ -6,7 +6,7 @@ const path = require('path');
 function OpenMctServerHandler(outputCallback) {
     // Create a child process spawn for later setting the NVM version and running the server
     this.childProcess = require('child_process');
-    this.processHandle = null;
+    this.processPID = undefined;
     this.outputCallback = outputCallback;
     this.nvmEnv = {};
 }
@@ -50,8 +50,8 @@ OpenMctServerHandler.prototype.start = function () {
     const embeddedThis = this;
 
     // Start the process
-    const execPath = path.join(process.cwd(), '..', 'openmctStaticServer');
-    let npmStart = this.childProcess.spawn('npm', ['start'], {shell: 'bash', cwd: execPath});
+    const wPath = path.join(process.cwd(), '..', 'openmctStaticServer');
+    let npmStart = this.childProcess.spawn('sh', ['runModule.sh'], {shell: 'bash', cwd: wPath, stdio: ['pipe','pipe','pipe','ipc']});
 
     // Set the output callbacks
     npmStart.stdout.on('data', function (data) {
@@ -63,26 +63,30 @@ OpenMctServerHandler.prototype.start = function () {
     npmStart.on('error', function (error) {
         embeddedThis.outputCallback('[OPEN-MCT STATIC SERVER] error: ' + error.message);
     });
+    npmStart.on('message', function (m) {
+        embeddedThis.outputCallback('[OPEN-MCT STATIC SERVER] ipc: ' + JSON.stringify(m));
+        embeddedThis.processPID = m.pid;
+    });
     npmStart.on('close', function (code) {
-        embeddedThis.processHandle = null;
+        embeddedThis.processPID = undefined;
         embeddedThis.outputCallback('[OPEN-MCT STATIC SERVER] close: ' + code);
     });
 
-    this.processHandle = npmStart;
     return {status: 'OK', message: 'Opem-MCT static server process started.'};
 }
 
-OpenMctServerHandler.prototype.stop = function () {
-    if (this.processHandle) {
-        this.processHandle.kill();
+OpenMctServerHandler.prototype.stop = function (signal) {
+    if (this.isOn()) {
+        process.kill(this.processPID,signal);
+        console.log('Killing PID %d with signal %s',this.processPID,signal);
         return {status: 'WRPLY', message: 'Process OpenMCT Server stopping...'};
     } else {
         return {status: 'WARNING', message: 'No process OpenMCT Server running...'};
     }
 }
 
 OpenMctServerHandler.prototype.isOn = function () {
-    return (this.processHandle != null);
+    return (this.processPID !== undefined);
 }
 
 function spawnSynchInOpenMCTserverPath(childProcess, shellCommand, cmdArgs) {

openmctStaticServer/runModule.sh

@@ -0,0 +1,4 @@
+. ${NVM_DIR}/nvm.sh
+nvm use v14.17.0
+node server.js
+

openmctStaticServer/server.js

@@ -14,6 +14,8 @@ app.use('/', staticServer);
 
 var port = process.env.PORT || 8080
 
+process.send({"pid": process.pid}); // Send the process PID back to the parent
+
 vizServer = app.listen(port, function () {
     console.log('iCub Telemetry Visualizer (Open MCT based) hosted at http://localhost:' + port);
 });