Using CouchDB

As of version 0.4 of the RabbitMQ webhooks plugin, you can interact with CouchDB’s HTTP REST API by sending JSON data as the body of an AMQP message. There are a few things you need to know to make this work easily.

Create a Document

To work with a document in CouchDB using the webhooks plugin, you’ll need to configure your URL to use a pattern. This is discussed on the Configuration page.

For example, given a CouchDB database named “test”, with a RabbitMQ broker running on the same machine (so the REST calls don’t need special permissions) as CouchDB, configure your URL like this:

http://localhost:5984/test/{id}

Using method “post” (set via configuration or passed as a message header named “method”), send an AMQP message to your configured queue with a message header named “id” set to the empty string "" with the following message body:

{ "test": "value", "number": 1 }

By passing the empty string as an id (rather than by leaving it undefined, which is definitely not what you want), the webhooks plugin will call URL http://localhost:5984/test/, which will create a new document with a generated id.

Updating a Document

Since the document can now appear in your views, you should be able to retrieve the new ID and revision number fairly easily. Otherwise you’ll have to wait until I have the callback code added to the plugin which will pass the JSON returned by CouchDB to the queue you specified on the original message in the replyTo field.

Once you have the document’s ID and revision, you can send another AMQP message with the updated JSON data as the body. This time you need to specify a message header named “id” which will cause the webhooks plugin to format your URL to http://localhost:5984/test/reallylongdocumentid. You’ll also want to specify a “method” of “put”, which tells CouchDB you want to update an existing document.

When issuing a PUT request, however, you need an attribute named “_rev” in your JSON that tells CouchDB what revision you’re updating. Your updated document would look like this example:

{ "_rev": "myreallylongrevisionid", "test": "updated value", "number": 2 }

Delete a Document

To delete a document from CouchDB, you need to do a little hack until I can figure out a better way of doing it.

Send an empty message to your AMQP webhooks queue with method header set to “delete” and specify an ID for the document but this time add a “rev=” query param to your ID string. Your ID should look like “reallylongdocumentid?rev=myreallylongrevisionid”.

Accessing Views

It wouldn’t make much sense to access a view inside CouchDB with the webhooks plugin yet. The response body that CouchDB sends back to the plugin is simply logged to the output right now. There’s still some more code to write before the plugin will return that data.

That being said, the webhooks plugin should be fully functional for doing bulk loads and updates from AMQP producers in parallel.