(DataFlex) Azure Service Bus - Peek-Lock Message (Non-Destructive Read)

See more Azure Service Bus Examples

Shows how to atomically retrieve and lock a message from a queue or subscription for processing. The message is guaranteed not to be delivered to other receivers (on the same queue or subscription only) during the lock duration specified in the queue/subscription description.

For more information, see https://docs.microsoft.com/en-us/rest/api/servicebus/peek-lock-message-non-destructive-read

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

Use ChilkatAx-win32.pkg

Procedure Test
    Handle hoRest
    Boolean iBAutoReconnect
    Boolean iSuccess
    Handle hoSbToken
    String sTopicName
    String sSubscriptionName
    Handle hoSbPath
    Handle hoSbQueuePath
    Variant vSbResponseBody
    Handle hoSbResponseBody
    Handle hoJsonBrokerProps
    String sMessage
    String sTemp1
    Integer iTemp1

    // Note: Requires Chilkat v9.5.0.65 or greater.

    // This requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // Make the initial connection.
    // A single REST object, once connected, can be used for many Azure Service Bus REST API calls.
    // The auto-reconnect indicates that if the already-established HTTPS connection is closed,
    // then it will be automatically re-established as needed.
    Get Create (RefClass(cComChilkatRest)) To hoRest
    If (Not(IsComObjectCreated(hoRest))) Begin
        Send CreateComObject of hoRest
    End
    Move True To iBAutoReconnect
    Get ComConnect Of hoRest "<yournamespace>.servicebus.windows.net" 443 True iBAutoReconnect To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoRest To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // ----------------------------------------------------------------------------------------------
    // The code above this comment could be placed inside a function/subroutine within the application
    // because the connection does not need to be made for every request.  Once the connection is made
    // the app may send many requests..
    // ----------------------------------------------------------------------------------------------

    // Let's load a previously computed SAS token and use it.
    // See Azure Shared Access Signature for an example to genenerate an Azure SAS token.
    Get Create (RefClass(cComChilkatStringBuilder)) To hoSbToken
    If (Not(IsComObjectCreated(hoSbToken))) Begin
        Send CreateComObject of hoSbToken
    End
    Get ComLoadFile Of hoSbToken "qa_data/tokens/serviceBusSas.txt" "utf-8" To iSuccess

    // Tell the REST object to use the Azure Shared Access Signature for authorization.
    Get ComPrepend Of hoSbToken "SharedAccessSignature " To iSuccess
    Get ComGetAsString Of hoSbToken To sTemp1
    Get ComAddHeader Of hoRest "Authorization" sTemp1 To iSuccess

    // ----------------------------------------------------------------------------------------------

    // Peek-lock a message from the subscription "feedings" in the topic "gilaMonster"
    Move "gilaMonster" To sTopicName
    Move "feedings" To sSubscriptionName

    // Build the path..
    Get Create (RefClass(cComChilkatStringBuilder)) To hoSbPath
    If (Not(IsComObjectCreated(hoSbPath))) Begin
        Send CreateComObject of hoSbPath
    End
    Get ComAppend Of hoSbPath "/" To iSuccess
    Get ComAppend Of hoSbPath sTopicName To iSuccess
    Get ComAppend Of hoSbPath "/subscriptions/" To iSuccess
    Get ComAppend Of hoSbPath sSubscriptionName To iSuccess
    Get ComAppend Of hoSbPath "/messages/head" To iSuccess

    // If peek-locking from a queue, the path would be built like this:
    Get Create (RefClass(cComChilkatStringBuilder)) To hoSbQueuePath
    If (Not(IsComObjectCreated(hoSbQueuePath))) Begin
        Send CreateComObject of hoSbQueuePath
    End
    Get ComAppend Of hoSbQueuePath "/" To iSuccess
    Get ComAppend Of hoSbQueuePath "queueName" To iSuccess
    Get ComAppend Of hoSbQueuePath "/messages/head" To iSuccess
    // This example will use the sbPath..

    // Add a timeout parameter.
    Get ComAddQueryParam Of hoRest "timeout" "20" To iSuccess

    // Use the POST HTTP verb to peek-lock the message.
    // Note that the only difference between the destructive Read-and-Delete and the non-destructive Peek-Lock
    // is that the HTTP verb.  (POST is for peek-lock, DELETE is fore read-and-delete.)
    Get Create (RefClass(cComChilkatStringBuilder)) To hoSbResponseBody
    If (Not(IsComObjectCreated(hoSbResponseBody))) Begin
        Send CreateComObject of hoSbResponseBody
    End
    Get ComGetAsString Of hoSbPath To sTemp1
    Get pvComObject of hoSbResponseBody to vSbResponseBody
    Get ComFullRequestNoBodySb Of hoRest "POST" sTemp1 vSbResponseBody To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoRest To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get ComResponseStatusCode Of hoRest To iTemp1
    Showln "Response Status Code = " iTemp1

    // Check for a success response.
    // CAREFUL: This returns a 201 response instead of a 200 response.  In general, either 200 or 201 should always indicate success.
    Get ComResponseStatusCode Of hoRest To iTemp1
    If (iTemp1 <> 201) Begin
        Get ComLastRequestStartLine Of hoRest To sTemp1
        Showln sTemp1
        Get ComLastRequestHeader Of hoRest To sTemp1
        Showln sTemp1
        Get ComGetAsString Of hoSbResponseBody To sTemp1
        Showln sTemp1
        Showln "Failed."
        Procedure_Return
    End

    // The content of the message is returned in the HTTP response body.
    // The HTTP response headers contains extra information.  For example:
    Get Create (RefClass(cComChilkatJsonObject)) To hoJsonBrokerProps
    If (Not(IsComObjectCreated(hoJsonBrokerProps))) Begin
        Send CreateComObject of hoJsonBrokerProps
    End
    Get ComResponseHdrByName Of hoRest "BrokerProperties" To sTemp1
    Get ComLoad Of hoJsonBrokerProps sTemp1 To iSuccess
    Set ComEmitCompact Of hoJsonBrokerProps To False
    Get ComEmit Of hoJsonBrokerProps To sTemp1
    Showln sTemp1

    // An example of the BrokerProperties JSON that is returned:

    // 	{
    // 	  "DeliveryCount": 2,
    // 	  "EnqueuedSequenceNumber": 3000003,
    // 	  "EnqueuedTimeUtc": "Wed, 07 Dec 2016 17:42:48 GMT",
    // 	  "Label": "M2",
    // 	  "LockToken": "0a13ee8a-be32-4458-89e0-5e1401caa6a0",
    // 	  "LockedUntilUtc": "Wed, 07 Dec 2016 18:13:12 GMT",
    // 	  "MessageId": "7bea513a6ddb49089e07bfbee26d85bd",
    // 	  "SequenceNumber": 3,
    // 	  "State": "Active",
    // 	  "TimeToLive": 922337203685.47754
    // 	}

    // Also the "Location" response header contains the URI of the locked message.
    // This can be used to ulock or delete the message.
    Get ComResponseHdrByName Of hoRest "Location" To sTemp1
    Showln "Location: " sTemp1

    // An example of the Location URI:
    // https://chilkat.servicebus.windows.net/gilamonster/subscriptions/feedings/messages/3/0a13ee8a-be32-4458-89e0-5e1401caa6a0

    // If successful, the message is the contents of the response body.
    Get ComGetAsString Of hoSbResponseBody To sMessage
    Showln "Received message: " sMessage

    Showln "Success."


End_Procedure