Interacting with Azure Queues Using REST

45 minutes
  • 2 Learning Objectives

About this Hands-on Lab

Azure Queues are a great way to provide reliable, cloud-based messaging between applications. There are multiple ways in which you can interact with Queues, including through the use of RESTful API calls. In this lab, you will have the opportunity to read from and write to an Azure Queue using the Azure Queue service REST API.

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

Save a list of the current messages to a file.
  1. Set up some environment variables to aid in generating a signature. For the storage_account and access_key, provide the actual storage account name and access key. One way to obtain these is to log in to the Azure portal. The access key can be found by clicking the storage account, then clicking Access Keys:
storage_account=${your storage account name}

access_key=${your storage account access key}

queue_name=incoming-items

request_date=$(TZ=GMT date "+%a, %d %h %Y %H:%M:%S %Z")

resource="/${storage_account}/${queue_name}/messages"

request_method="GET"

headers="x-ms-date:$request_date"
  1. Generate a signature and Authorization header:
string_to_sign="${request_method}nnnn${headers}n${resource}"

hex_key="$(echo -n $access_key | base64 -d -w0 | xxd -p -c256)"

signature=$(printf "$string_to_sign" | openssl dgst -sha256 -mac HMAC -macopt "hexkey:$hex_key" -binary |  base64 -w0)

authorization_header="SharedKey $storage_account:$signature"
  1. Make a request to peek the current messages in the queue, redirecting the output to a file:
curl -s -X $request_method 
  -H "x-ms-date:$request_date" 
  -H "Authorization:$authorization_header" 
  "https://${storage_account}.queue.core.windows.net/${queue_name}/messages?peekonly=true&numofmessages=32" 
  > /home/cloud_user/messages.txt
  1. Check the contents of the file to see the messages:
cat /home/cloud_user/messages.txt

You should see some XML representing one existing message.

Manually add the lost data to the queue.
  1. Set up some environment variables to aid in generating a signature.
request_date=$(TZ=GMT date "+%a, %d %h %Y %H:%M:%S %Z")

resource="/${storage_account}/${queue_name}/messages"

request_method="POST"

content_type="application/x-www-form-urlencoded; charset=utf-8"

storage_service_version="2018-11-09"

headers="x-ms-date:$request_datenx-ms-version:$storage_service_version"

message="Item 4489: Coin Collection"

message_base64=$(echo $message | base64)

message_xml="<QueueMessage><MessageText>$message_base64</MessageText></QueueMessage>"

message_length=${#message_xml}
  1. Generate a signature and Authorization header.
string_to_sign="${request_method}nnn$message_lengthnn$content_typennnnnnn${headers}n${resource}nmessagettl:-1"

hex_key="$(echo -n $access_key | base64 -d -w0 | xxd -p -c256)"

signature=$(printf "$string_to_sign" | openssl dgst -sha256 -mac HMAC -macopt "hexkey:$hex_key" -binary |  base64 -w0)

authorization_header="SharedKey $storage_account:$signature"
  1. Make a request to peek the current messages in the queue, redirecting the output to a file.
curl -X $request_method 
  -H "x-ms-date:$request_date" 
  -H "x-ms-version:$storage_service_version" 
  -H "Content-Type:$content_type" 
  -H "Authorization:$authorization_header" 
  --data "$message_xml" 
  "https://${storage_account}.queue.core.windows.net/${queue_name}/messages?messagettl=-1"
  1. If you wish, you can check the Queue in Azure Portal to verify that your new message appears.

Additional Resources

Your company, Store All the Things!, is using Azure Queues to handle real-time messages involving items coming into their storage warehouse. One such queue, called incoming-items, is used by some applications which have recently had some issues. To recover from these issues, you need to do two things using the Azure Queue service REST API:

  • Save a list of the current messages in the queue to a file for auditing. You can save the raw data as there is no need to decode or parse it.
  • Manually add a new message to the queue that was lost due to a failure in one of the applications that writes to the queue.

You will need the following additional information:

  • The name of the storage account that contains the queue begins with the text storagewh.
  • The Queue is called incoming-items.
  • Save the current list of messages in a file at /home/cloud_user/messages.txt.
  • Manually add a message to the Queue with the following content: Item 4489: Coin Collection.

If you get stuck, feel free to check out the solution video, or the detailed instructions under each objective. Good luck!

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