@neuralegion/os-service

os-service

This module implements the ability to run a Node.js based JavaScript program as a native Windows or Linux service.

This module is installed using node package manager (npm):

# This module contains C++ source code which will be compiled
# during installation on Windows platforms using node-gyp.  A
# suitable build chain must be configured on Windows platforms
# before installation.

npm i @neuralegion/os-service

It is loaded using the require() function:

const service = require('@neuralegion/os-service');

A program can then be added, removed and run as a service:

service.add('my-service');

service.remove('my-service');

service.run(() => {
  // Stop request received (i.e. a kill signal on Linux or from the
  // Service Control Manager on Windows), so let's stop!
  service.stop();
});

Batch Service Creation

Two approaches can be taken when adding and removing services.

In the first approach a program can be responsible for adding, removing and starting itself as a service. This is typically achieved by supporting program arguments such as --add, --remove, and --run, and executing the appropriate action.

The following example adds the calling program as a service when called with a --add parameter, and removes the created service when called with a --remove parameter:

if (process.argv[2] == '--add') {
  service.add('my-service', { args: [process.argv[1], '--run'] }, (error) => {
    if (error) {
      console.trace(error);
    }
  });
} else if (process.argv[2] == '--remove') {
  service.remove('my-service', (error) => {
    if (error) {
      console.trace(error);
    }
  });
} else if (process.argv[2] == '--run') {
  service.run(() => service.stop(0));

  // Run service program code...
} else {
  // Show usage...
}

Note the --run argument passed in the options parameter to the service.add() function. When the service is started using the Windows Service Control Manager, or the Linux service management facilities, the first argument to the program will be --run. The above program checks for this and if specified runs as a service using the service.run() function.

Also note that neither the node binary or the programs fully qualified path are specified. These parameters are automatically calculated it not specified. Refer to the service.add() function description for details about how this works.

In the second approach a dedicated service management program can be responsible for adding and removing many services in batch. The program adding and removing services is not a service itself, and would never call the service.run() function.

The following example adds or removes number of services:

if (program.argv[2] == '--add') {
  service.add('service1', { args: ['c:examplesvc1.js'] }, (error) => {
    if (error) {
      console.trace(error);
    } else {
      service.add('service2', { args: 'c:examplesvc2.js' }, (error) => {
        if (error) {
          console.trace(error);
        }
      });
    }
  });
} else {
  service.remove('service2', (error) => {
    if (error) {
      console.trace(error);
    } else {
      service.remove('service1', (error) => {
        if (error) {
          console.trace(error);
        }
      });
    }
  });
}

Note that unlike the previous example the --run argument is not passed in the options parameter to the service.add() function. Since each service program does not add or remove itself as a service it only needs to run, and as such does not need to be told to so.

Also note that the programPath argument is passed in the options parameter to the service.add() function, to specify the fully qualified path to each service program - which would otherwise default to the service management program adding the services.

Each of the service programs can simply start themselves as services using the following code:

service.run(() => service.stop(0));

// Run service program code...

Running Service Programs

When a service program starts it can always call the service.run() function regardless of whether it is started at the console, by the Windows Service Control Manager, or the Linux service management facilities.

On Windows, when the service.run() function is called this module will attempt to connect to the Windows Service Control Manager so that control requests can be received - so that the service can be stopped. When starting a program at the console an attempt to connect to the Windows Service Control Manager will fail. In this case the service.run() function will assume the program is running at the console and silently ignore this error.

On Linux, services started at the console will run in the foreground, this allows command sequences such as CTRL+C to be used, e.g. during development. When Linux services are started using the Linux service management facilities, i.e. service my-service start, they can be stopped using the signals SIGINT and SIGTERM, or again using the Linux service management facilities, i.e. service my-service stop.

This behaviour results in a program which can be run either at the console, the Windows Service Control Manager, or the Linux service management facilities with no change.

Current Working Directory

Upon starting the current working directory of a service program will be platform specific, e.g. the "%windir%\system32" directory on Windows. Service programs need to consider this when working with relative directory and file paths.

This path will most likely be different when running the same program at the console, so a service program may wish to change the current working directory to a more suitable location using the process.chdir() function to avoid different behaviour between the two methods of starting a program.

Using This Module

This module attempts to behave in exactly the same way on Windows and Linux platforms - at least the API is exactly the same for both platforms both from a service management and service running perspective.

On Windows platforms the Windows Service Control Manager WIN32 API is used to manage services. On Linux platforms a systemd unit is created if it is available, otherwise the chkconfig command is used. If chkconfig is not available the update-rc.d command is tried instead.

service.add (name, [options], cb)

The add() function adds a service.

The name parameter specifies the name of the created service. The optional options parameter is an object, and can contain the following items:

• displayName - The services display name, defaults to the name parameter
  • this parameter will be used on Windows platforms only
• command - The command used to run the service (i.e. c:\Program Files\nodejs\node.exe, defaults to the value of process.execPath
• args - An array of strings specifying parameters, defaults to []
• runLevels - An array of numbers specifying Linux run-levels at which the service should be started for Linux platforms, defaults to [2, 3, 4, 5], this is only used when chkconfig or update-rc.d is used to install a service
• username - For Windows platforms a username and password can be specified, the service will be run using these credentials when started, see the CreateService() functions win32 API documentation for details on the format of the username, on all other platforms this parameter is ignored
• password - See the username parameter
• systemdWantedBy - For when systemd will be used a target can be specified for the WantedBy attribute under the [Install] section in the generated systemd unit file, defaults to multi-user.target
• dependencies - An array of strings specifying other services this service depends on, this is optional

The service will be set to automatically start at boot time, but not started. The service can be started using the net start "my-service" command on Windows and service my-service start on Linux.

The cb callback function is called once the service has been added. The following arguments will be passed to the callback function:

• error - Instance of the Error class, or null if no error occurred

The following example installs a service named my-service, it explicitly specifies the services display name, and specifies a number of parameters to the program:

const options = {
  displayName: 'MyService',
  args: [process.argv[1], '--server-port', 8888],
  username: '.Stephen Vickers',
  password: 'MyPassword :)'
};

service.add('my-service', options, (error) => {
  if (error) {
    console.trace(error);
  }
});

service.remove (name, cb)

The remove() function removes a service.

The name parameter specifies the name of the service to remove. This will be the same name parameter specified when adding the service.

The service must be in a stopped state for it to be removed. The net stop "my-service" command can be used to stop the service on Windows and the service my-service stop on Linux before it is to be removed.

The cb callback function is called once the service has been removed. The following arguments will be passed to the callback function:

• error - Instance of the Error class, or null if no error occurred

The following example removes the service named my-service:

service.remove('my-service', (error) => {
  if (error) {
    console.trace(error);
  }
});

service.run (callback)

The run() function will attempt to run the program as a service.

NOTE When run the service will NOT make any changes to the process.stdout and process.stderr streams. Users are required to utilise whatever logging modules they require to managing process logging and its destination. Older versions of this module (versions before 2.0.0) would support re-directing these streams to a specific writeable stream, support for that was removed in version 2.0.0.

The callback function will be called when the service receives a stop request, e.g. because the Windows Service Controller was used to send a stop request to the service, or a SIGTERM signal was received.

The program should perform cleanup tasks and then call the service.stop() function.

The following example starts a program as a service:

service.run(() => service.stop(0));

service.stop ([rcode])

The stop() function will cause the service to stop, and the calling program to exit.

Once the service has been stopped this function will terminate the program by calling the process.exit() function, passing to it the rcode parameter which defaults to 0. Before calling this function ensure the program has finished performing cleanup tasks.

BE AWARE, THIS FUNCTION WILL NOT RETURN.

The following example stops the calling program specifying a return code of 0, the function will not return:

service.run(() => service.stop(0));

Example Programs

Example programs are included under the modules example directory.

License

Copyright (c) 2021 NeuraLegion [e-mail]

Copyright (c) 2018 NoSpaceships Ltd [e-mail]

Copyright (c) 2014 Stephen Vickers [e-mail]

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.