Installing Packages

You can add functionality to your flow by installing Linux or npm packages. The steps to install a package and to protect against upgrades varies, depending on the type of package you plan to install.

Installing NPM Packages

Npm packages can be installed in two ways: from the Flow Editor or from the terminal, both described below. After installing a package, it can be called in a function node.

Installing npm packages from the Flow Editor

1.Open the flow you want to modify in the Flow Editor.
2.Add a function node to the flow, then double-click it to edit the node. Or edit an existing function node.
3.In the Function text box, enter a comment that includes the npm install command in the form // npm install <package-name>
For example: // npm install mathjs
4.Deploy the flow.
The package is installed and automatically saved to the flow's package.json as a project dependency. This ensures that this module is re-installed when the flow is upgraded.

After installing the module, the version number of the module is appended to the end of the comment in the function node. For example:
 

// npm install mathjs@3.5.3

To install a newer package version, update the number listed in the comment, then deploy the flow: the module updates to the version you specified.

Installing npm packages from the terminal

1.Open a terminal for the flow, then change directory to /home/flow/src/flow - all npm packages must be installed in this directory.
If you start from a new terminal window, you can enter cd src/flow to navigate to this directory.
2.Enter npm install <package_name> --save
Including the --save flag is essential: it adds the specified module as a dependency to your flow’s package.json and ensures that this module is re-installed when the flow is upgraded.
For example, to install the npm package left-pad, enter: npm install left-pad --save

Verifying your flow dependencies

Whether you install npm packages from the Flow Editor or from a terminal, you can check the success of the installation by viewing the contents of the flow's package.json file, located in the flow's /home/flow/src/flow directory.

To view the contents of package.json:

1.Open a terminal for the flow, then change directory to /home/flow/src/flow.
If you start from a new terminal window, you can enter cd src/flow to navigate to this directory.
2.To view the contents of the flow's package.json file, enter:
cat package.json
The contents display in the terminal window.

For example, if you installed the mathjs npm module, the contents would look something like this:
 

{                                                                               

  "name": "flow",                                                               

  "version": "1.0.0",                                                           

  "description": "",                                                            

  "dependencies": {                                                             

    "mathjs": "^3.5.3"                                                          

  }                                                                             

} 

 

To view a list of global npm packages available in the flow, open a terminal, and enter: npm list -g --depth=0

Installing Linux Packages

Several Linux packages are installed with every flow instance. To view a list of all Linux packages currently installed, including your packages plus the default packages, enter: dpkg -l

To install additional Linux packages:

1.Open a terminal for the flow.
2.Enter sudo apt-get install <package-name>
For example, to install the package pdftools, enter: sudo apt-get install pdftools
3.Add the install line to the flow's upgrade script to ensure that this package is reinstalled when the flow is upgraded:
a.From the terminal, change directory to /home/flow/src/flow.
If you start from a new terminal window, you can enter cd src/flow to navigate to this directory.
b.Open upgrade.sh for editing.
You can use slap (enter slap upgrade.sh) or vim (enter vim upgrade.sh) to edit the file.
c.Add the terminal commands used to install the packages before the exit call in upgrade.sh.
For example, this sample script includes commands to install the pdftools and tree Linux packages following an upgrade:
 

#!/bin/bash     
# This script is run the first time your container started
# and when your container is upgraded
sudo apt-get install pdftools
sudo apt-get install tree
echo 'Upgrade script complete'  
exit 0            

 

d.Save your changes.