The main project page for Fog can be found at http://dmohl.github.com/Fog/.

Fog brings the cloud down to earth and wraps it in something more easily used by F#. It provides a more functional approach to creating Windows Azure apps with F#.

Building Azure apps with Fog that need to interact with Azure Table Storage, Blob Storage, Queue Storage, Caching, and/or the Service Bus is very easy with the help of a few configuration settings that have specific names. The examples that follow use this approach. Fog also provides more fine-grained interaction if that is desired. See the integration tests for examples.

Blob Storage

With Fog all you have to do to interact with Azure blob storage is to add the connection string information in the config with a name of "BlobStorageConnectionString". Once that is done, you can use syntax like the following:

UploadBlob "testcontainer" "testblob" "This is a test" |> ignore
DeleteBlob "testcontainer" "testblob"

or

UploadBlob "testcontainer" "testblob" testBytes |> ignore
DownloadBlob<byte[]> "testcontainer" "testblob"

Table Storage

The simplest way to interact with Azure table storage is to add the connection string information in the config with a name of "TableStorageConnectionString". Once that is done, you can use syntax like the following:

[<DataServiceKey("PartitionKey", "RowKey")>]
type TestClass() = 
	let mutable partitionKey = ""
	let mutable rowKey = ""
	let mutable name = ""
	member x.PartitionKey with get() = partitionKey and set v = partitionKey <- v
	member x.RowKey with get() = rowKey and set v = rowKey <- v
	member x.Name with get() = name and set v = name <- v

let originalClass = TestClass( PartitionKey = "TestPart", RowKey = Guid.NewGuid().ToString(), Name = "test" )

CreateEntity "testtable" originalClass |> ignore

let newClass = originalClass
newClass.Name <- "test2"
UpdateEntity "testtable" newClass |> ignore

DeleteEntity "testtable" newClass

Queue Storage

For queue storage, add the connection string configuration value with setting name "QueueStorageConnectionString".

AddMessage "testqueue" "This is a test message" |> ignore
let result = GetMessages "testqueue" 20 5
for m in result do
    DeleteMessage "testqueue" m

Service Bus

There are a few service bus related config entries. Here's the list of expected names: ServiceBusIssuer, ServiceBusKey, ServiceBusScheme, ServiceBusNamespace, ServiceBusServicePath

To send a message do this:

type TestRecord = { Name : string }

let testRecord = { Name = "test" } 

SendMessage "testQueue" testRecord

To receive a message, pass the queue name, a function to handle successful message retrieval, and another function to handle errors.

HandleMessages "testQueue"
    <| fun m -> printfn "%s" m.GetBody<TestRecord>().Name
    <| fun ex m -> raise ex        

To use topics in a pub/sub type of scenario, use something like the following to subscribe:

Subscribe "topictest2" "AllTopics4"
    <| fun m -> printfn "%s" m.GetBody<TestRecord>().Name
    <| fun ex m -> raise ex        

Message publishing can be accomplished like this:

Publish "topictest2" testRecord

A few other handy functions include Unsubscribe and DeleteTopic:

Unsubscribe "topictest2" "AllTopics4"
DeleteTopic "topictest2"

Caching

Adding items to cache can be done with code such as the following (note: you'll need to get everything setup and add the web or app.config settings as described at https://www.windowsazure.com/en-us/develop/net/how-to-guides/cache/ ):

[<DataContract>]
type TestRecord = 
	{ [<DataMember>] mutable Id : Guid
	  [<DataMember>] mutable Name : string }

let testRecord = { Id = Guid.NewGuid(); Name = "Dan" }

let key = testRecord.Id.ToString()  
Put key testRecord |> ignore

You can also specify a timeout value for the cache outside of the default 48 hours with code like this:

PutWithCustomTimeout key testRecord 10 |> ignore

Gettig the value from cache is done like this:

let result = Get<TestRecord> key

Fog is available on NuGet Gallery as id Fog.

• 0.1.4.1 - Strong-names the Fog assembly.
• 0.1.3.0 - Includes Azure Caching related functions and several bug fixes.
• 0.1.0.0 - Is the initial release which provides support for Azure table, blob, and queue storage as well as Service Bus Queues and Topics.

• Add additional async functions
• Add code-based and convention based configuration

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The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

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