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Azure functions

Node.js Microsoft Azure functions for the Biodiversity Net Gain service.

Extension bundles are used to ensure the function app uses a compatible set of binding extensions.

Prerequisites

Common dependencies

Prerequisite dependencies used by multiple packages within this repository are documented in Prerequisites

Local development prerequisites

Azure Function Core Tools

Function triggers

  • HTTP based triggering is used:
    • when starting to submit an application to the Biodiversity Net Gain public register.
    • processing uploads to the service.
    • submitting an application to the Biodiversity Net Gain public register.

App settings / environment variables for deployment to Microsoft Azure

name description mandatory
APPINSIGHTS_INSTRUMENTATIONKEY Instrumentation key controlling if telemetry is sent to the ApplicationInsights service Y
APPLICATIONINSIGHTS_CONNECTION_STRING ApplicationInsights service connection string used by the function app Y
AZURE_STORAGE_ACCOUNT Microsoft Azure storage account name Y
AZURE_STORAGE_ACCESS_KEY Microsoft Azure storage account shared access key Y
AzureWebJobsStorage Storage account connection string Y
FUNCTIONS_EXTENSION_VERSION Functions runtime version (must be ~4) Y
FUNCTIONS_WORKER_RUNTIME The language worker runtime to load in the function app (must be node) Y
WEBSITE_CONTENTAZUREFILECONNECTIONSTRING Connection string for storage account where the function app code and configuration are stored in event-driven scaling plans running on Windows Plan dependent
WEBSITE_CONTENTSHARE The file path to the function app code and configuration in an event-driven scaling plan on Windows Plan dependent
WEBSITE_NODE_DEFAULT_VERSION Default version of Node.js (must be ~16)
OPERATOR_SB_CONNECTION_STRING Operator integration tier service bus connection string Y
POSTGRES_HOST Postgres host eg localhost Y
POSTGRES_USER Postgres user eg postgres Y
POSTGRES_PASSWORD Postgres password eg postgres Y
POSTGRES_DATABASE Database name eg bng Y
POSTGRES_PORT Postgres port eg 5432 Y
POSTGRES_SSL_MODE Postgres SSL Mode eg require or blank N
PROCESS_UNTRUSTED_ATTEMPTS Count of attempts of process Untrusted (purpose is to replay AV scanning issues) defaults to 5 N

App settings / environment variables for use with Azurite

When connecting to an Azurite container a local.settings.json template file containing a compatible set of app settings must be used as a starting point. This template file:

  • excludes all app settings / environment variables providing connecivity to Microsoft Azure services
  • includes app settings / environment variables required to provide connecivity between the Azurite container and:
    • Azure Functions
    • GDAL software called by Azure Functions
  • uses the hostname azurite to ensure connectivity to an Azurite container when the Azure Functions runtime is used in a containerised environment.
    • When connecting from Azure Functions in a non-containerised local environment, the hostname azurite must resolve to the local IP address of the host machine.
  • uses the hostname azure_services to ensure connectivity to the custom container running the Azure SignalR emulator and Azure functions core tools
    • When connecting from Azure Functions in a non-containerised local environment, the hostname azure_services must resolve to the local IP address of the host machine.
  • contains placeholders for sensitive values (such as those used to provide connectivity to threat screening services).

Run the following NPM script within the directory containing this file or the root directory of the whole mono repository to copy the template file into the directory containing this file.

npm run local:install

The copied file is included in the set of files ignored by git.

To reduce the risk of the template file being edited such that sensitive values are included and pushed to version control accidentally, detect-secrets must be installed. If using a Visual Studio Code development container, detect-secrets is installed by defsult. If using a local development environment built manually, detect-secrets must be installed manually.

Once a copy of the template file is in place and placeholders for sensitive values are populated, the Azure functions can be run with connectivity to Azurite. If connectivity to Microsoft Azure infrastructure is requird during local development, the copy of local.settings.json in the same directory as this file must be reconfigured accordingly.

To switch between connection to Microsoft Azure infrstructure and an Azurite container, the creation of a symbolic link called local.settings.json within the directory containing this file which refererences the required local.settings.json file is recommended.

Mandatory Azurite specific app settings /environment variables

name description
AZURE_BLOB_SERVICE_URL URL used to access the Azurite blob service
AZURE_QUEUE_SERVICE_URL URL used to access the Azurite queue service
AZURE_STORAGE_CONNECTION_STRING Connection string linking GDAL and Azurite

Installation

The following activities need to be performed for the functions to run. While the documentation states what activities need to be performed it does not prescribe how the activities should be performed.

  • Ensure that all prerequisites exist.
  • Configure app settings / environment variables.
  • Install node modules.
  • To run the functions in a Microsoft Azure environment, deploy the functions to a function app.
  • To run the functions in a local environment issue the command func start from the directory containing this file.
    • This command requires local installation of Azure Function Core Tools as defined in the Local prerequisites section above.