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README.md

👉 Alert (Fan-out)

| Create Client Certificates | Configure Event Grid Namespaces | Configure Mosquitto | Run the Sample |

This scenario shows how to send a weather alert to a vehicle fleet. Instead of sending one message to each vehicle, the message is sent to a topic that is subscribed by all vehicles. This is a fan-out scenario. Additionally, to avoid missing any message in case of losing network connectivity, the vehicles are using a persistent session, this way the broker will keep the messages until the vehicle is connected again. The sender uses the MessageExpiryInterval to make the alert available for 5 minutes.

Client Role Operation Topic/Topic Filter
control-tower sender pub vehicles/weather/alert
vehicle04 receiver sub vehicles/weather/alert
vehicle05 receiver sub vehicles/weather/alert

The message will send the following payload:

{
	"type": "Weather",
	"alert": "Heavy rain",
	"time": "2023-06-23T10:34:00Z"
}

🔒 Create Client Certificates

Run the following step commands to create the client certificates for vehicle04, vehicle05 and control-tower clients.

# from folder scenarios/alert
step certificate create \
    vehicle04 vehicle04.pem vehicle04.key \
    --ca ~/.step/certs/intermediate_ca.crt \
    --ca-key ~/.step/secrets/intermediate_ca_key \
    --no-password --insecure \
    --not-after 2400h

step certificate create \
    vehicle05 vehicle05.pem vehicle05.key \
    --ca ~/.step/certs/intermediate_ca.crt \
    --ca-key ~/.step/secrets/intermediate_ca_key \
    --no-password --insecure \
    --not-after 2400h

step certificate create \
    control-tower control-tower.pem control-tower.key \
    --ca ~/.step/certs/intermediate_ca.crt \
    --ca-key ~/.step/secrets/intermediate_ca_key \
    --no-password --insecure \
    --not-after 2400h

📐 Configure Event Grid Namespaces

Event Grid Namespaces requires to register the clients, and the topic spaces to set the client permissions.

Create the clients

The clients will be created based on the certificate subject, you can register the 3 clients in the portal or by running the script below:

# from folder scenarios/alert
source ../../az.env

az resource create --id "$res_id/clients/vehicle04" --properties '{
    "authenticationName": "vehicle04",
    "state": "Enabled",
    "clientCertificateAuthentication": {
        "validationScheme": "SubjectMatchesAuthenticationName"
    },
    "attributes": {
            "type": "vehicle"
    },
    "description": "This is a test client"
}'

az resource create --id "$res_id/clients/vehicle05" --properties '{
    "authenticationName": "vehicle05",
    "state": "Enabled",
    "clientCertificateAuthentication": {
        "validationScheme": "SubjectMatchesAuthenticationName"
    },
    "attributes": {
            "type": "vehicle"
    },
    "description": "This is a test client"
}'

az resource create --id "$res_id/clients/control-tower" --properties '{
    "authenticationName": "control-tower",
    "state": "Enabled",
    "clientCertificateAuthentication": {
        "validationScheme": "SubjectMatchesAuthenticationName"
    },
    "attributes": {
            "type": "control-tower"
    },
    "description": "This is a test client"
}'

Configure topic spaces and permission bindings

# from folder scenarios/alert
az resource create --id "$res_id/topicSpaces/vehicles" --properties '{
    "topicTemplates": ["vehicles/#"]
}'

az resource create --id "$res_id/permissionBindings/vehiclesPub" --properties '{
    "clientGroupName":"$all",
    "topicSpaceName":"vehicles",
    "permission":"Publisher"
}'

az resource create --id "$res_id/permissionBindings/vehiclesSub" --properties '{
    "clientGroupName":"$all",
    "topicSpaceName":"vehicles",
    "permission":"Subscriber"
}'

Create the .env files with connection details

The required .env files can be configured manually, we provide the script below as a reference to create those files, as they are ignored from git.

# from folder scenarios/alert
source ../../az.env
host_name=$(az resource show --ids $res_id --query "properties.topicSpacesConfiguration.hostname" -o tsv)

echo "MQTT_HOST_NAME=$host_name" > vehicle04.env
echo "MQTT_USERNAME=vehicle04" >> vehicle04.env
echo "MQTT_CLIENT_ID=vehicle04" >> vehicle04.env
echo "MQTT_CERT_FILE=vehicle04.pem" >> vehicle04.env
echo "MQTT_KEY_FILE=vehicle04.key" >> vehicle04.env
echo "MQTT_CLEAN_SESSION=false" >> vehicle04.env

echo "MQTT_HOST_NAME=$host_name" > vehicle05.env
echo "MQTT_USERNAME=vehicle05" >> vehicle05.env
echo "MQTT_CLIENT_ID=vehicle05" >> vehicle05.env
echo "MQTT_CERT_FILE=vehicle05.pem" >> vehicle05.env
echo "MQTT_KEY_FILE=vehicle05.key" >> vehicle05.env
echo "MQTT_CLEAN_SESSION=false" >> vehicle05.env

echo "MQTT_HOST_NAME=$host_name" > control-tower.env
echo "MQTT_USERNAME=control-tower" >> control-tower.env
echo "MQTT_CLIENT_ID=control-tower" >> control-tower.env
echo "MQTT_CERT_FILE=control-tower.pem" >> control-tower.env
echo "MQTT_KEY_FILE=control-tower.key" >> control-tower.env

🪰 Configure Mosquitto

To establish the TLS connection, the CA needs to be trusted, most MQTT clients allow to specify the ca trust chain as part of the connection, to create a chain file with the root and the intermediate use:

# from folder _mosquitto
cat ~/.step/certs/root_ca.crt ~/.step/certs/intermediate_ca.crt > chain.pem
cp chain.pem ../scenarios/alert

The chain.pem is used by mosquitto via the cafile settings to authenticate X509 client connections.

# from folder scenarios/alert
echo "MQTT_HOST_NAME=localhost" > vehicle04.env
echo "MQTT_CLIENT_ID=vehicle04" >> vehicle04.env
echo "MQTT_CERT_FILE=vehicle04.pem" >> vehicle04.env
echo "MQTT_KEY_FILE=vehicle04.key" >> vehicle04.env
echo "MQTT_CA_FILE=chain.pem" >> vehicle04.env
echo "MQTT_CLEAN_SESSION=false" >> vehicle04.env

echo "MQTT_HOST_NAME=localhost" > vehicle05.env
echo "MQTT_CLIENT_ID=vehicle05" >> vehicle05.env
echo "MQTT_CERT_FILE=vehicle05.pem" >> vehicle05.env
echo "MQTT_KEY_FILE=vehicle05.key" >> vehicle05.env
echo "MQTT_CA_FILE=chain.pem" >> vehicle05.env
echo "MQTT_CLEAN_SESSION=false" >> vehicle05.env

echo "MQTT_HOST_NAME=localhost" > control-tower.env
echo "MQTT_CLIENT_ID=control-tower" >> control-tower.env
echo "MQTT_CERT_FILE=control-tower.pem" >> control-tower.env
echo "MQTT_KEY_FILE=control-tower.key" >> control-tower.env
echo "MQTT_CA_FILE=chain.pem" >> control-tower.env

To use mosquitto without certificates: change the port to 1883 and disable TLS

# from folder scenarios/alert
echo "MQTT_HOST_NAME=localhost" > vehicle04.env
echo "MQTT_CLIENT_ID=vehicle04" >> vehicle04.env
echo "MQTT_TCP_PORT=1883" >> vehicle04.env
echo "MQTT_USE_TLS=false" >> vehicle04.env
echo "MQTT_CLEAN_SESSION=false" >> vehicle04.env

echo "MQTT_HOST_NAME=localhost" > vehicle05.env
echo "MQTT_CLIENT_ID=vehicle05" >> vehicle05.env
echo "MQTT_TCP_PORT=1883" >> vehicle05.env
echo "MQTT_USE_TLS=false" >> vehicle05.env
echo "MQTT_CLEAN_SESSION=false" >> vehicle05.env

echo "MQTT_HOST_NAME=localhost" > control-tower.env
echo "MQTT_CLIENT_ID=control-tower" >> control-tower.env
echo "MQTT_TCP_PORT=1883" >> control-tower.env
echo "MQTT_USE_TLS=false" >> control-tower.env

🎲 Run the Sample

All samples are designed to be executed from the root scenario folder.

dotnet

To build the dotnet sample run:

# from folder scenarios/alert
dotnet build dotnet/alert.sln

To run the dotnet sample execute each line below in a different shell/terminal.

# from folder scenarios/alert
 dotnet/vehicle/bin/Debug/net7.0/vehicle --envFile=vehicle04.env
 dotnet/vehicle/bin/Debug/net7.0/vehicle --envFile=vehicle05.env
 dotnet/control_tower/bin/Debug/net7.0/control_tower --envFile=control-tower.env

C

TBD

python

TBD