- sql subscription

implementations-sql.md

@@ -39,7 +39,13 @@ The queue configuration is part of the specified uri, e.g.:
 
 Contains a sql-based `ISubscriptionManager` implementation.  The subscription manager caches all subscriptions forever so should a new subscriber be added be sure to restart the publisher endpoint service.
 
-There is also a subscription specific configuration section:
+# Supported providers
+
+Currently only the `System.Data.SqlClient` provider name is supported but this can easily be extended.  Feel free to give it a bash and please send a pull request if you *do* go this route.  You are welcome to create an issue and assistance will be provided where able.
+
+## Configuration
+
+The configuration section is optional as the defaults will be applied when no section is provided.
 
 ```xml
 <configuration>
@@ -49,7 +55,7 @@ There is also a subscription specific configuration section:
 
 	<subscription
 		connectionStringName="Subscription"
-		ignoreSubscribe="false"
+		subscribe="Normal|Ensure|Ignore"
 	/>
   .
   .
@@ -59,10 +65,15 @@ There is also a subscription specific configuration section:
 
 | Attribute | Default	| Description | Version Introduced |
 | --- | --- | --- | --- |
-| connectionStringName	 | Subscription | The name of the `connectionString` to use to connect to the subscription store. | |
-| ignoreSubscribe			 | false		| If `true` the `ISubscriptionManager.Subscribe` method is ignored; else new subscription request are honored. | v6.0.9 |
+| `connectionStringName`	 | Subscription | The name of the `connectionString` to use to connect to the subscription store. | |
+| `subscribe`	| Normal | Indicates how calls to the `Subscribe` method are dealt with: `Normal` is the ***default*** and will subscribe to the given message type(s) if they have not been subscribed to yet.  `Ensure` will check to see that the subscription exists and if not will throw an `ApplicationException`.  `Ignore` will simply ignore the subscription request.
+| <strike>ignoreSubscribe</strike>			 | false		| *Obsolete*: use the `subscribe` option. | v6.0.9 |
+
+Whenever the endpoint is configured as a worker no new subscriptions will be registered against the endpoint since any published events should be subscribed to only by the distributor endpoint.  When using a broker such as RabbitMQ all the endpoints feed off the same work queue uri and any of the endpoints could create the subscription.
+
+When moving to a non-development environment it is recommended that you make use of the `Ensure` option for the `subscribe` attribute since any change to the work queue uri will result in possible duplicate subscriptions.  
 
-Whenever the endpoint is configured as a worker no new subscriptions will be registered against the endpoint since any published events should be subscribed to only by the distributor endpoint.  However, there may be scenarios where one uses a broker, such as RabbitMQ, and there is no distributor endpoint since each endpoint can consume messages from the inbox queue.  In such situation one would either configure a specific endpoint as a subscriber where new subscriptions can be made, or configure the subscriptions manually using scripts or [Shuttle.Sentinel](https://shuttle.github.io/shuttle-sentinel/).
+For any environment you could manually configure subscription using either scripts or or [Shuttle.Sentinel](https://shuttle.github.io/shuttle-sentinel/) once it becomes feasible.
 
 The `SubscriptionManager` will register itself using the [container bootstrapping](http://shuttle.github.io/shuttle-core/overview-container/#Bootstrapping).