{"id":1601,"date":"2019-06-12T22:18:29","date_gmt":"2019-06-12T14:18:29","guid":{"rendered":"https:\/\/www.techcoil.com\/blog\/?p=1601"},"modified":"2021-01-10T13:12:44","modified_gmt":"2021-01-10T05:12:44","slug":"how-to-use-nssm-to-run-a-python-3-application-as-a-windows-service-in-its-own-python-3-virtual-environment","status":"publish","type":"post","link":"https:\/\/www.techcoil.com\/blog\/how-to-use-nssm-to-run-a-python-3-application-as-a-windows-service-in-its-own-python-3-virtual-environment\/","title":{"rendered":"How to use NSSM to run a Python 3 application as a Windows Service in its own Python 3 virtual environment"},"content":{"rendered":"

If you want to run a Python 3 application as a Windows Service, then you are going to love NSSM<\/a>. Since NSSM handles the life cycle of a Windows Service for our Python 3 application, we can keep it platform agnostic. <\/p>\n

Previously, we saw how we can use a Python 3 virtual environment in Windows 10<\/a>. Given that, let's see how we can use NSSM to run a Python 3 application as a Windows Service in its own Python 3 virtual environment.<\/p>\n

Creating a sample Python 3 application<\/h2>\n

In order to simplify this tutorial, let's attempt to run the Python 3 Flask application with an API endpoint that generates a QR Code image<\/a> as a Windows Service.<\/p>\n

In addition to that, let us place requirements.txt<\/strong> and run_app.py<\/strong> into the %systemdrive%%homepath%\\Documents\\qr-code-app<\/code> folder.<\/p>\n

Contents of requirements.txt<\/h3>\n
\r\nflask-restplus==0.12.1\r\nPillow==6.0.0\r\nqrcode==6.1\r\n<\/pre>\n
Contents of run_app.py<\/h3>\n
\r\nfrom flask import Flask, Blueprint, request, send_file\r\nfrom flask_restplus import Api, Namespace, Resource, fields\r\n# import library to help us with file IO\r\nfrom io import BytesIO\r\n \r\nimport os, qrcode\r\n \r\n# Create Flask app\r\napp = Flask(__name__)\r\n \r\n# Associate Api with Blueprint\r\napi_blueprint = Blueprint('API', __name__)\r\napi = Api(api_blueprint,\r\n    title='Api for QR code app',\r\n    version='1.0',\r\n    description='This is an API for QR code app',\r\n    # All API metadatas\r\n)\r\n \r\n# Create namespace for containing Qr Code related operations\r\nqrcode_namespace = Namespace('QrCode', description='Qr code related operations')\r\n# Specify uri of qrcode namespace as \/qrcode\r\napi.add_namespace(qrcode_namespace, path='\/qrcode')\r\n# Specify uri of api blueprint as \/api\r\napp.register_blueprint(api_blueprint, url_prefix='\/api')\r\n \r\n# Define input model\r\nqrcode_creation_input = qrcode_namespace.model('QRCode creation Input', {\r\n    'value': fields.String(required=True, description='The value that is supposed to be encoded into qrcode'),\r\n})\r\n \r\n \r\n# Define API endpoint for creating Qr Code image\r\n@qrcode_namespace.route('\/')\r\n@qrcode_namespace.doc('Creates a QRCode image based on a string value.')\r\nclass QrCodeRoot(Resource):\r\n \r\n    @qrcode_namespace.expect(qrcode_creation_input)\r\n    @qrcode_namespace.produces(['image\/png'])\r\n    @qrcode_namespace.response(200, description='Return QR Code png image file.')\r\n    @qrcode_namespace.response(400, description='Invalid input provided.')\r\n    def post(self):\r\n \r\n        # Get value to encode into QR Code\r\n        json_input = request.get_json()\r\n        value_to_turn_into_qrcode = json_input['value']\r\n \r\n        # Create qr code image and return it as HTTP response\r\n        pil_img = qrcode.make(value_to_turn_into_qrcode)\r\n        img_io = BytesIO()\r\n        pil_img.save(img_io, 'PNG')\r\n        img_io.seek(0)\r\n        return send_file(img_io, mimetype='image\/png')\r\n \r\n \r\nif __name__ == '__main__':\r\n    port = int(os.getenv("PORT", "5678"))\r\n    app.run(host='0.0.0.0', port=port)\r\n<\/pre>\n
Preparing the virtual environment to run our Python 3 application<\/h2>\n
Before continuing on, be sure to go through the tutorial on how to use a Python 3 virtual environment in Windows 10<\/a>. After you had gone through the tutorial, you would have installed Python 3 on your Windows machine. In addition to that, you will understand how to create, activate and install dependencies into a virtual environment.<\/p>\n
Creating the virtual environment to run our Python 3 application<\/h3>\n
Given these points, let us first create the virtual environment to run our Python 3 application. In order to do so, start a command prompt window and type in the following command:<\/p>\n
\r\npython -m venv "%systemdrive%%homepath%\\Documents\\qr-code-app-env"\r\n<\/pre>\n
After the command completes, you will find the Python 3 virtual environment within the %systemdrive%%homepath%\\Documents\\qr-code-app-env<\/code> folder.<\/p>\n
Installing the application dependencies into the virtual environment<\/h3>\n
Next, activate your Python 3 virtual environment by running the following command:<\/p>\n
\r\n"%systemdrive%%homepath%\\Documents\\qr-code-app-env\\Scripts\\activate.bat"\r\n<\/pre>\n
After your Python 3 virtual environment got activated, run the following command to install the Python dependencies for the application:<\/p>\n
\r\npip install -r "%systemdrive%%homepath%\\Documents\\qr-code-app\\requirements.txt"\r\n<\/pre>\n
When the dependencies are installed, you will be able to run your Python application within the virtual environment.<\/p>\n
Creating the .bat<\/code> file to run our Python 3 application in its own virtual environment<\/h2>\n
At this point in time, you are ready to create a .bat<\/code> file to start your application within the virtual environment. Given that, create a run_app.bat<\/code> in the %systemdrive%%homepath%\\Documents\\qr-code-app<\/code> folder with the following content:<\/p>\n
\r\ncall ..\\qr-code-app-env\\Scripts\\activate.bat\r\ncall python run_app.py\r\n<\/pre>\n
Downloading a copy of NSSM<\/h2>\n
After you had created the windows batch file to run the your Python application within the virtual environment, proceed to download NSSM<\/a>. Save the .zip<\/code> file and extract its content. After extracting the content, you will find a nssm.exe<\/code> file inside the win32<\/code> and win64<\/code> folder. <\/p>\n
Depending on whether your Windows is 32 bit or 64 bit<\/a>, you will use the corresponding nssm.exe<\/code> file to install your Python application as a Windows Service.<\/p>\n
For the purpose of this tutorial, let's assume that we want to use the nssm.exe<\/code> in the C:\\nssm-2.24\\win64<\/code><\/strong> folder.<\/p>\n
Run a command prompt instance as administrator<\/h2>\n
In order to avoid being prompted for administrator access for subsequent calls to C:\\nssm-2.24\\win64<\/code>, let's run a command prompt instance as administrator. <\/p>\n
\"Finding<\/p>\n
We will run the subsequent commands in this command prompt instance.<\/p>\n
Installing your Python application as a Windows Service with nssm.exe<\/h2>\n
Given that our nssm.exe is located in C:\\nssm-2.24\\win64<\/code>, we can then use the following command to install our Python application as a Windows Service:<\/p>\n
\r\nC:\\nssm-2.24\\win64\\nssm install qrcodeapp "%systemdrive%%homepath%\\Documents\\qr-code-app\\run_app.bat"\r\n<\/pre>\n
When you run the command, NSSM will install your Python 3 application as a Windows Service.<\/p>\n
At this point in time, your Windows Service is not yet started<\/strong>.<\/p>\n
Enabling log files for your Python 3 application<\/h2>\n
When you start your Windows Service at this point in time, it will not generate any log files when it runs.<\/p>\n
Therefore, let's configure it to channel application output to log files.<\/p>\n
In order to do so, first start NSSM service editor<\/strong> with the following command:<\/p>\n
\r\nC:\\nssm-2.24\\win64\\nssm edit qrcodeapp\r\n<\/pre>\n
After the command run, NSSM service editor<\/strong> will appear for enabling log files for your Python 3 application.<\/p>\n
\"nssm-2.24<\/p>\n
Given that, click on the I\/O<\/strong> tab and enter the paths that you want the log files to appear:<\/p>\n
\"nssm-2.24<\/p>\n
Once you are done with that, click Edit service<\/strong>.<\/p>\n
Starting your Python application as a Windows Service<\/h2>\n
In order to start the Windows Service for your Python application, run the following command:<\/p>\n
\r\nC:\\nssm-2.24\\win64\\nssm start qrcodeapp\r\n<\/pre>\n
Since Startup Type<\/strong> for the Windows Service is set to Automatic<\/strong>, our Python 3 Flask application will run automatically when we had started our Windows machine.<\/p>\n
Further usages of NSSM<\/h2>\n
At this point in time, we will have fulfilled our goal of using NSSM to run a Python 3 application as a Windows Service in its own Python 3 virtual environment.<\/p>\n
In addition to what I had covered, the nssm.exe contains several other functionalities.<\/p>\n
In case you need to use other functionalities of NSSM, you can refer to NSSM usage page<\/a> for more information.<\/p>\n\n