IoTEdgeEnvTestSolution

Demonstration of reading custom environment variables by an Azure ioT Edge module.

When the module starts, a number of environment variables are read.

Note: This includes the already used Azure IoT Edge module specific variables. Check the example below.

Docker container

The current docker container is available at 'svelde/envtestmodule:0.0.1-amd64' (Please check Docker Hub for more recent versions).

Envrionment variables

The current implementation looks for these variables:

• variableString
• variableJSON

if one of these is not available, it will be marked are missing.

variableString

Just past any string.

variableJSON

Pass a JSON formatted text with these two variables:

{
    "someInteger" : 42,
    "someString" : "Hello module"
}

Example output

This is tested with these environment variables:

The following output is to be expected:

IoT Hub module client initialized.
Start reading environment variables:
GetEnvironmentVariables: 
  IOTEDGE_GATEWAYHOSTNAME = edge-device-test-weu-vm
  IOTEDGE_DEVICEID = MessageTest1-1
  IOTEDGE_WORKLOADURI = unix:///var/run/iotedge/workload.sock
  DOTNET_RUNNING_IN_CONTAINER = true
  IOTEDGE_MODULEGENERATIONID = 637933928617587066
  IOTEDGE_AUTHSCHEME = sasToken
  ASPNETCORE_URLS = http://+:80
  HOME = /home/moduleuser
  PATH = /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
  variableString = HelloVariable
  IOTEDGE_IOTHUBHOSTNAME = xyz.azure-devices.net
  variableJSON = { "someInteger" : 42, "someString" : "Hello module" }
  HOSTNAME = ef033
  IOTEDGE_MODULEID = envtest
  IOTEDGE_APIVERSION = 2019-01-30
  RuntimeLogLevel = Information

Found 'HelloVariable'
Found '{ "someInteger" : 42, "someString" : "Hello module" }', containing '42' and 'Hello module'
End reading environment variables.

As you can see, both the Azure IoT Edge module specific variables and our custom environment variables are shown.

Usage

This is an alternative to sending Desired properties allthough the impact is there.

The environment variable can only be updated using the Deployment manifest. Each time a deployment manifest is sent, all (other) modules will reload their desired properties.