Can a date and time be specified when sending data

问题:

Here's the scenario. I'm not working with real-time data. Instead, I get data from my electric company for the past day's electric usage. Specifically, each day I can get # of kwhs for each hour on the clock on the past day.

So, I'd like to load this past information into event hub each following day. Is this doable? Does event hub support loading past information, or is it only and forever about realtime streaming data, with no ability to load past data in?

I'm afraid this is the case, as I've not seen any date specification in what limited api documentation I could find for it. I'd like to confirm, though...

Thanks, John

回答1:

An Azure Event Hub is really meant for short-term storage. By default you may only retain data up to 7 days. After which the data will be deleted based upon an append timestamp that was created when the message first entered the Event Hub. Therefore it is not practical to use an Azure Event Hub for data that's older than 7 days.

An Azure Event Hub is meant for message/event management, not long term storage. A possible solution would be to write the Event Hub data to an Azure SQL server or blob storage for long term storage. Then use Azure Stream Analytics (an event processor) to join the active stream with the legacy data that has accumulated on the SQL server. Also note, you can call this appended attribute. It's called "EventEnqueuedUtcTime". Keep in mind that it will be on the server time, whose clock may be different from the date/time of actual measurement.

As for appending a date time. If you are sending it in as a JSON, just simply append it as a key and message value. Example Message with Time: { "Time": "My UTC Time here" }

回答2:

A streaming system of this type doesn't care about times a particular application may wish to apply to the items. There simply isn't any processing that happens based on a time field unless your code does it.

Each message sent is an EventData which contains a message with an arbitrary set of bytes. You can easily include a date/time in that serialized data structure, but EventHubs won't care about it. There is no sorting performed or fixed ordering other than insertion order within a partition which is defined by the sequence number. While the enqueued time is available it's mostly useful for monitoring how far behind in processing you are.

As to the rest of your problem, I'd agree with the comment that EventHubs may not really be the best choice. You can certainly load data into it once per day, but if it's really only 24 data points/day, it's not really the appropriate technology choice unless it's a prototype/tech demo for a system that's eventually supposed to have a whole load of smart meters reporting to it with fair frequency. (Note also that EventHubs cost $11/month minimum, Service Bus Queue $10/Month min, and AWS SQS $0 min)