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I have an IoT device that sends data in a binary format to an IoT Hub.
From there, I need to store the data in Cosmos DB, after presumably converting it to JSON format.
My idea has been to set up an Azure Function with an IoT Hub trigger and a Cosmos DB output. The function code itself would handle the data conversion.
Does this seem like an appropriate approach? I was going to use a Cosmos DB Table but saw somewhere that the Function App output bindings only support the SQL API, is that true?
For reference, I have a JavaScript code to convert from binary to JSON, and my IoT hub is successfully receiving the device messages and triggering the Function App.
Any help is greatly appreciated,
Thank you
@Matt Heagerty Just following up here to see if my response helps
Apologies for not seeing your previous response right away. Yes this does help very much. Now I can focus on implementing the solution rather than worrying if I'm using the correct services. Thank you very much.
Yes. That is a perfect approach for your scenario.
And it is true that the bindings support only the SQL API. You could still use the CosmosDB SDK as-is in your function app without leveraging the browser if you required a different API though. While this is OK for input/output bindings, triggers would not work.
Thank you again for your previous help. I now have an Azure function successfully receiving IoT data, decoding it, and sending it to Cosmos SQL. Each function execution is creating multiple JSON objects and calling the output binding every time a JSON object is built (see example below)
for (i = 0; i < 10; i++){
var item = JSON.stringify({
"tag" : 'Count',
"value" : i
}); // end JSON object
context.bindings.outputDocument = item;
} // end for loop
This logic results in only the final execution of the loop sending one JSON object (where "value" = 9) to CosmosDB. Can the output binding only be called once? What is the best way to approach sending multiple JSON objects in one Azure function execution?
Thank you
This is indeed possible. You must use an array of documents instead of one. And in the loop, you would add each one to the array like this
context.bindings.outputDocument= [];
for (i = 0; i < 10; i++){
var item = JSON.stringify({
"tag" : 'Count',
"value" : i
}); // end JSON object
context.bindings.outputDocument.push(item);
} // end for loop
Thank you. That sample chunk of code is successfully sending multiple JSON objects to CosmosDB. Shown below is the actual structure of my function with pieces taken out for clarity and conciseness.
module.exports = async function (context, req) {
context.bindings.outputDocument = [];
count= [1, 2, 3, 4, 5];
count.forEach(processSingleRecord);
function processSingleRecord(record) {
var item = JSON.stringify({
"tag" : 'Count',
"value" : record
}); // end JSON object
// Set the output binding data from the item
context.bindings.outputDocument.push(item);
};
context.done();
};
Upon running, I receive an error saying "...Value cannot be null. (Parameter 'document')". I am confused by why this code structure does not work and would appreciate any insight. This function uses an HTTP trigger but has the same structure and yields the same error.