An Azure Event Hub client that is easy to use and performs well. From a local machine, I'm able to sustain ~300 single messages per second from a single client. When running in an Azure VM in the same region as the Event Hubs instance, I was able to send ~400 single messages per second. From a Raspberry PI, I was able to send ~40 single messages per second.
There is an option for batching messages if needed by using the sendMessages
function.
eventHubs.init({
hubNamespace: eventHubsNamespace,
hubName: eventHubsHubName,
keyName: eventHubsKeyName,
key: eventHubsKey
});
var deviceMessage = {
Temperature: 45.2,
Pressure: 23.7
}
eventHubs.sendMessage({
message: deviceMessage,
deviceId: 1,
});
Note: deviceId is simply a unique name to identify your device to Azure. If not given, you will recieve a 401 Authorization failed response.
When you initialize the event hubs client, it's advisable to use a SAS token in a production environment. This is a revokable key that is unique to the device. You can generate a token programatically, or online using this form.
eventHubs.init({
hubNamespace: eventHubsNamespace,
hubName: eventHubsHubName,
sasToken: sasToken
});
For batching multiple messages and sending them together in single REST call, use the sendMessages
function:
eventHubs.sendMessages({
messages: [], // array of messages
deviceId: 1,
});
Beware that Azure EventHub REST API has a limit of 256kb for batching (per call), so make sure you batched messages do not reach this limit (otherwise an error will be returned).
npm install eventhubs-js
Don't forget to update your package.json
file.
Performance was optimized in a number of ways:
- Setting
http.globalAgent.maxSockets = 50;
increases the HTTP connection pool, which allows us to create more connections to serve messages that need sent. If you don't send a large volume of messages, no problem, the pool will remain relatively empty. - Caching the SAS Tokens. I haven't tested the performance of the node.js crypto libraries and moment time calculations, but it was easy enough to cache the generated SAS tokens to avoid recalcuating on each message.
- Automatic recreation of cached token just before it expires
Promises allow you to chain calls without "callback hell":
eventHubs.sendMessage({
message: deviceMessage,
deviceId: 1,
}).then(function() {
console.log('Message Sent!');
});
Promises also allow us to kick of multiple send requests simultaneously, and easily manage the results:
var promise, promises;
for (i = 0; i < iterations; i++) {
promise = eventHubs.sendMessage({
message: deviceMessage,
deviceId: 1,
});
promises.push(promise);
}
Q.allSettled(promises).then(function () {
console.log('All Messages Sent!');
});
- https://git.allseenalliance.org/cgit/core/alljoyn-js.git/tree/
- https://github.com/noodlefrenzy/event-hub-client
Microsoft Developer Experience & Evangelism
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