fbnconfig 0.0.69

fbnconfig is a python library (and commandline tool) to allow a declarative description of a LUSID environment

fbnconfig

fbnconfig is a Python library (and commandline tool) to allow a declarative description of a LUSID environment. It allows you to specify the desired state and, when you deploy, it converges the LUSID environment to your desired state by creating, updating, or deleting entities within LUSID so that the LUSID environment and the desired state match.

Getting started

fbnconfig is available from PyPi

pip install fbnconfig

Running the command

fbnconfig -e https://foo.lusid.com -t <token> run path/to/script.py

This will apply the deployment script (script.py) to the foo.lusid.com domain.

For a list of commands that let you view what's already deployed, use fbnconfig --help.

Authentication

fbnconfig needs a valid LUSID url and a token to create and modify a LUSID environment. The token will most likely be a personal access token (PAT), but could be a token from an authentication exchange. For more information on PATs and how to create them, start by reading What is a personal access token? on FINBOURNE's Knowledge Base.

We recommend configuring the url and token as environment variables:

FBN_ACCESS_TOKEN=xyzabc1234
LUSID_ENV=https://foo.lusid.com
fbnconfig setup

Alternatively, you can use the commandline:

fbnconfig -e https://foo.lusid.com -t xyzabc1234 setup

One time setup

Before being able to run a deployment, a one time per-domain setup is required. This creates a required CustomEntityDefinition where deployment logs are stored.

To run using the cli, assuming the appropriate environment variables are set, then run the following:

fbnconfig setup

To run using the library:

import fbnconfig
import os

lusid_env = os.environ["LUSID_ENV"]
token = os.environ["FBN_ACCESS_TOKEN"]
client = fbnconfig.create_client(lusid_env, token)
fbnconfig.setup(client)

Writing the deployment script

A fbnconfig configure script is a Python file that includes the configure(env): function. When you create an fbnconfig configure script, you must define one or more Deployments.

For example, the following code is a valid fbnconfig configure script. The configure script defines the desired state, and running it changes the remote LUSID environment to match.

from fbnconfig import drive
from fbnconfig import Deployment


def configure(env):
    f1 = drive.FolderResource(id="base_folder", name="my_folder", parent=drive.root)
    return Deployment("my_deployment", [f1])

• Configure scripts need to import references resource like a normal Python script would.
• The configure(env): function is the entrypoint, which should return a Deployment.
• Deployments contain one or more resources. In this case, the Deployment contains a single FolderResource Resource that's saved in the f1 variable.

When we run this script the first time it will create a folder in LUSID Drive called my_folder. The second time we run it, fbnconfig knows the folder already exists and will not make any changes. If we change the name of the folder (for example name="another_name") and run fbnconfig again it will rename the folder in LUSID Drive.

Deployment and Resource Ids

Deployments require an id. In this example we define a value of my_deployment for the Deployment's id when we return the Deployment object.

Be careful if you change the ID of a Deployment. If you change the ID and re-run the configure script, fbnconfig creates a new LUSID environment with a new Deployment ID and new Resources. The previous Deployment's Resources are not automatically removed.

Each Resource must also have an id and these ids must be unique within the fbnconfig Deployment. In this example, we use id="base_folder" to uniquely identify the folder Resource we create.

• We can change the name of a folder and it will get renamed because it has the same id.
• If we change the id then the existing folder will be deleted and a new one will be created. Note that the original folder does not persist, because fbnconfig configure scripts are declarative fbnconfig makes the LUSID state match the configure file state. If the original folder disappears from the configure file, fbnconfig makes the original folder disappear from the corresponding LUSID environment.
• The Python variable f1 that references the folder is only used to identify the resource within the Python configure script. This variable is not used for tracking changes in LUSID, therefore changing the Python variable names does not affect what gets deployed.

Dependencies

Resources may need to reference other resources. For example, the following code creates the nested folder Resources.

def configure(env):
    f1 = drive.FolderResource(id="base_folder", name="my_folder", parent=drive.root)
    f2 = drive.FolderResource(id="sub_folder", name="my_subfolder", parent=f1)
    return Deployment("my_deployment", [f1, f2])

If we run this it will create the structure /my_folder/my_subfolder. Using the Python variable names we say that my_subfolder (f1 in the script) is a subfolder of its parent my_folder (f2 in the script). Relationships are defined by the Python variables, in this case parent=f1.

When we have nested structures like this, fbnconfig creates the parents before the children. For example, f1 would get created (or updated) before f2, and if they are removed from the deployment then f2 will be deleted before f1.

This example references both folders ([f1, f2]), however we could instead reference just the subfolder ([f2]). Because f2 depends on f1, f1 will be implicitly included.

Dependencies outside the deployment

When we define a Deployment in a configure script and use fbnconfig to create the corresponding LUSID environment, all the underlying Resources are fully managed by fbnconfig. This means we want to use fbnconfig to manage all related Resources within a single Deployment.

However, if we need to establish a relationship between existing Resources and our configure script, we can use a Ref. In the following example, we account for the downloads folder which already exists because it has been created manually or is part of another Deployment.

def configure(env):
    f1 = drive.FolderRef(id="downloads", name="downloads")
    f2 = drive.FolderResource(id="sub_folder", name="my_subfolder", parent=f1)
    return Deployment("my_deployment", [f1, f2])

• This code will create sub_folder within the existing downloads Resource. We tell fbnconfig that downloads already exists by using the drive.FolderRef() function instead of drive.FolderResource().
• If downloads doesn't exist at the time this is run, we get an error.
• The downloads folder will be the parent of sub_folder, but it won't be managed within this Deployment.
• If f1 is removed, it won't get deleted because it is not being managed in this deployment.

The vars file

To aid with using the same script for dev, uat, and prod, fbnconfig takes a commandline argument to a json file called the "vars file". The vars file (called env in the examples above) is parsed and passed into the configure function.

For example, suppose we wanted to use different email for dev and prod (like the environment variable example above).

We would:

1. Create two vars files.

// prod.json                                    // dev.json
{                                               {
    "email": "[e-mail]"                     "email": "[e-mail]"
}                                               }

1. Reference the files from the script var env.

   def configure(env):
       export_user = identity.UserResource(
           id="user2",
           ...
           emailAddress=env.email,
       )
   

2. Run the following command to use the [e-mail] email..

   fbnconfig -e https://dev.lusid.com -v dev.json script.py
   

These vars files can be comitted to the repo to capture variations between environments. For secrets, it's better to use explicit environment variables in the script (see below).

Using Python in the script

A deployment script is normal Python, so Python language features are available. For example variables and f-strings. To allow values to depend on the environment, you can use os.environ to initialise the variables. This is useful when setting up secrets in the config store.

For example, the following code:

1. Passes the secret as an environment variable.
2. Makes an http request or use a library from a vault provider to source the secret.
3. Uses the secret inside the configure function.

import os

company = os.environ["company"]

def configure(env):
    export_user = identity.UserResource(
        id="user2",
        ...
        emailAddress=f"exports@{company}",
        login=f"exports@{company}",
    )

You can even create resources in a loop, for example:

def configure(env):
    folders = [
        drive.FolderResource(id=f"folder_{i}", name="i", parent=drive.root)
        for i in range(0, 10)
    ]
    return Deployment('ten-folders', folders)

The Python variables for the Resources need to be added to the deployment and each Resource must have a unique id.

Using fbnconfig as a library

Using fbnconfig from the commandline dyamically loads your Python script and executes the Deployment. In some cases (for example using fbnconfig as part of another application) you can call it from Python as well.

The following example creates an empty deployment called "my-jobs":

from os import environ
from fbnconfig import Deployment, deploy


def configure(env):
    return Deployment("my-jobs", [])


host_vars = {}
lusid_url = "https://foo.lusid.com"
token = environ["MY_TOKEN_VAR"]
deployment = configure(host_vars)
deploy(deployment, lusid_url, token)