Added PID support

bin/cli

@@ -7,6 +7,8 @@
 const program = require('commander');
 const pkg = require('../package.json');
 const dotenv = require('dotenv');
+const fs = require('fs');
+const util = require('../util');
 
 //==============================================================================
 // Setting up the program command line arguments.
@@ -15,6 +17,7 @@ const dotenv = require('dotenv');
 program
   .version(pkg.version)
   .option('-c, --config [path]', 'Specify the configuration file to load')
+  .option('--pid [path]', 'Specify a path to output the current PID to')
   .parse(process.argv);
 
 if (program.config) {
@@ -27,6 +30,40 @@ if (program.config) {
   }
 }
 
+// If the `--pid` flag is used, put the current pid there.
+if (program.pid) {
+  let pidPath = program.pid;
+
+  if (!/\//.test(pidPath)) {
+    if (!/\.pid/.test(pidPath)) {
+      pidPath += '.pid';
+    }
+    pidPath = `/tmp/${pidPath}`;
+  }
+
+  fs.writeFile(pidPath, `${process.pid.toString()}\n`, (err) => {
+    if (err) {
+      console.error(`Can't write PID file: ${err}`);
+      throw err;
+    }
+
+    // Add the cleanup for the fs onto the shutdown.
+    util.onshutdown([
+      () => new Promise((resolve, reject) => {
+
+        // Remove the pid file.
+        fs.unlink(pidPath, (err) => {
+          if (err) {
+            return reject(err);
+          }
+
+          return resolve();
+        });
+      })
+    ]);
+  });
+}
+
 // Perform rewrites to the runtime environment variables based on the contents
 // of the process.env.REWRITE_ENV if it exists. This is done here as it is the
 // entrypoint for the entire application.
@@ -43,4 +80,15 @@ program
 // If there is no command listed, output help.
 if (!process.argv.slice(2).length) {
   program.outputHelp();
+  return;
 }
+
+// The ensures that the child process that is created here is always cleaned up
+// properly when the parent process dies.
+util.onshutdown([
+  (signal) => {
+    if ((program.runningCommand.killed === false) && (program.runningCommand.exitCode === null)) {
+      program.runningCommand.kill(signal);
+    }
+  }
+]);