(Excel) 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

Download Excel Class Modules Chilkat Excel Class Modules

' 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.
Dim rest As Chilkat.Rest
Set rest = Chilkat.NewRest

bAutoReconnect = True

success = rest.Connect("<yournamespace>.servicebus.windows.net",443,True,bAutoReconnect)
If (success <> True) Then
    Debug.Print rest.LastErrorText
    Exit Sub
End If

' ----------------------------------------------------------------------------------------------
' 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.
Dim sbToken As Chilkat.StringBuilder
Set sbToken = Chilkat.NewStringBuilder
Dim success As Boolean
success = sbToken.LoadFile("qa_data/tokens/serviceBusSas.txt","utf-8")

' Tell the REST object to use the Azure Shared Access Signature for authorization.
success = sbToken.Prepend("SharedAccessSignature ")
success = rest.AddHeader("Authorization",sbToken.GetAsString())

' ----------------------------------------------------------------------------------------------

' Peek-lock a message from the subscription "feedings" in the topic "gilaMonster"

topicName = "gilaMonster"

subscriptionName = "feedings"

' Build the path..
Dim sbPath As Chilkat.StringBuilder
Set sbPath = Chilkat.NewStringBuilder
success = sbPath.Append("/")
success = sbPath.Append(topicName)
success = sbPath.Append("/subscriptions/")
success = sbPath.Append(subscriptionName)
success = sbPath.Append("/messages/head")

' If peek-locking from a queue, the path would be built like this:
Dim sbQueuePath As Chilkat.StringBuilder
Set sbQueuePath = Chilkat.NewStringBuilder
success = sbQueuePath.Append("/")
success = sbQueuePath.Append("queueName")
success = sbQueuePath.Append("/messages/head")
' This example will use the sbPath..

' Add a timeout parameter.
success = rest.AddQueryParam("timeout","20")

' 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.)
Dim sbResponseBody As Chilkat.StringBuilder
Set sbResponseBody = Chilkat.NewStringBuilder
success = rest.FullRequestNoBodySb("POST",sbPath.GetAsString(),sbResponseBody)
If (success <> True) Then
    Debug.Print rest.LastErrorText
    Exit Sub
End If

Debug.Print "Response Status Code = "; rest.ResponseStatusCode

' 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.
If (rest.ResponseStatusCode <> 201) Then
    Debug.Print rest.LastRequestStartLine
    Debug.Print rest.LastRequestHeader
    Debug.Print sbResponseBody.GetAsString()
    Debug.Print "Failed."
    Exit Sub
End If

' The content of the message is returned in the HTTP response body.
' The HTTP response headers contains extra information.  For example:
Dim jsonBrokerProps As Chilkat.JsonObject
Set jsonBrokerProps = Chilkat.NewJsonObject
success = jsonBrokerProps.Load(rest.ResponseHdrByName("BrokerProperties"))
jsonBrokerProps.EmitCompact = False
Debug.Print jsonBrokerProps.Emit()

' 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.
Debug.Print "Location: "; rest.ResponseHdrByName("Location")

' 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.

message = sbResponseBody.GetAsString()
Debug.Print "Received message: "; message

Debug.Print "Success."