Azure EventHub hook support

[lokisisland]

As discussed on Slack recently, we have added EventHub hook support. We have tested this running the code in this branch with real data and the messages are being written successfully to the event hub.

[tidwall]

Hi,

Thanks for the PR.

While Looking at the docs for this feature:

https://github.com/tile38/tile38.github.io/pull/51/files#diff-9f58aacff06286b39e375539999a852b7227957dd1dc45801cc7d25d2d6fdd11R244

I see that URL for the endpoint looks a little different that a standard URL.

Endpoint=sb://event-hub-namespace.windows.net/;SharedAccessKeyName=sharedAccessKeyName;SharedAccessKey=***Secret***;EntityPath=event-hub-name

I was expecting something like:

eventhub://event-hub-namespace.windows.net?SharedAccessKeyName=sharedAccessKeyName&SharedAccessKey=***Secret***&EntityPath=event-hub-name

Is this due to an EventHub requirement on Azures side?

[lokisisland]

Hey,

Yes, the whole argument is a connection string rather than a URI; the connection string does contain the URI but there are other elements required as well. The connection string is comprised of the Endpoint (URI), SharedAccessKeyName (name of the access key to follow), SharedAccessKey (the access key) and EntityPath (Azure parlance for what is, in effect, the queue name). The connection string uses semi-colons to delimit each section, and each section is of the form SectionName=SectionValue. If we removed the "Endpoint=" at the beginning, we'd have to add it again to make the connection string valid.

Full details of an EventHub connection string can be found at: https://docs.microsoft.com/en-us/azure/event-hubs/event-hubs-get-connection-string.

We thought it best to allow users to provide the full connection string (rather than specifying fields separately via query args like are currently implemented for Kafka connections) as the connection string in full is provided in the Azure UI. To provide the fields separately would require the user to break down the connection string just for the software to recombine it, thus increasing the likelihood of error.

I hope this makes sense! Let me know if not :)

[tidwall]

Yes, the URI connection string starting with "Endpoint=" makes sense.
Though I wonder if though if we shouldn't allow both "Endpoint=sb://..." and "sb://..." interchangeably?

[tidwall]

lgtm :)