Azure Service bus topic: why messages seem to be eaten by receiver? - node.js

Question

I have a service bus topic that ingest telemetry messages outgoing from one of my servers ('telemetry-topic') at a rate of approximately 1 message every 10 seconds.
I have a web (site) front that subscribes to the 'telemetry-subscription' that consumes the 'telemetry-topic'.
What I witness is that the more front I run, the least message frequency it receives. I sounds like my topic acts as a queue…
What I should see is that any front -no matter the number of them— should sustain de approx 1 message very 10 seconds.
Note: My stack is node.
The receiver:
async function serviceBusTelemetrySubscribe(props) {
const module = '🚌 Service bus telemetry'
const {enter, leave, log, warn, error} = SDK.logFunctions(module, {
verboseLevel: 1,
verboseEnterLeave: true,
})
try {
enter()
log('Subscribing with given processMessage', props.processMessage, 'processError', props.processError)
const {processMessage, processError} = props
// connection string to your Service Bus namespace
const connectionString = 'XXXX'
// == Topic & subscription names
const topicName = 'telemetry-topic'
const subscriptionName = 'telemetry'
// == Create a Service Bus client using the connection string to the Service Bus namespace
const sbClient = new ServiceBusClient(connectionString)
log('Service bus client', sbClient)
// == Create a receiver for "all telemetry" subscription.
const receiver = sbClient.createReceiver(topicName, subscriptionName)
log('Service bus receiver for subscription name "', subscriptionName, '" is:', sbClient)
// == Function to handle messages, which provide a default one
const myMessageHandler = processMessage || (async (messageReceived) => {
log(`received message: ${messageReceived.body}`)
})
// == Function to handle any errors, which provide a default one
const myErrorHandler = processError || (async (error) => {
error(error)
})
log('Subscribing with actual processMessage', myMessageHandler, 'processError',myErrorHandler)
// == Subscribe and specify the message and error handlers
const sbSubscription = receiver.subscribe({
processMessage: myMessageHandler,
processError: myErrorHandler
})
log('Service bus subscription', sbSubscription)
// == Return cleanup method
return async () => {
log('Closing Service bus…')
// Waiting long enough before closing the sender to send messages
await delay(5000)
log('Closing Service bus subscription…')
await sbSubscription.close()
log('Closing Service bus receiver…')
await receiver.close()
log('Closing Service bus client…')
await sbClient.close()
}
}
catch(err) {
error(err)
}
finally {
leave()
}
}