Using an Azure APIM Policy to call an OAuth endpoint and cache the token

Recently I have been involved as the Integration Architect and tech lead for a project to integrate between MS Dynamics 356  AX/CRM and 3rd party systems.

One of the challenges was to provide single endpoints for internal systems calling web services outside of the organisation that utilised OAuth2.0.  This is where a consumer normally has to call an OAuth token endpoint first and then append the token to the request before calling the actual web service.

By using APIM as a proxy and policies in APIM, I managed to achieve the goal of providing a single URL endpoint for the consumer. The policy initially gets the token from the authorisation endpoint, caches the token and then passes the token to the web service being called. This process is known as fragment caching, where parts of the responses are cached for subsequent requests. Also by caching the bearer part of the token improved the performance significantly for subsequent calls.

Below were the steps I used to add a web API to create transfers orders in Dynamics AX and a policy using the Azure APIM management portal.

1. First create the properties for the oAuth clientId and client secret. A good tip is to prefix the property name and set the Tags with the name of the API you are calling. This helps latter on when you have multiple properties to manage.image

The Properties page should look like something like below after adding your custom properties:

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2. Next, go to the API’s page to either add or import the API’s definition you are calling. Here I am just going to add the API manually by first entering the name, API endpoint address and the public facing URL suffix. Remember to add it to an existing product.

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3. After the API has been created we will then add the operations. For this demo I will just add one operation to create a transfer order.

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4. Now that the API we wish to call has been added to the APIM service we can finally pay our attention to creating a policy which does the background task of obtaining the OAuth token. Here I will setup a policy on the CreateTransferOrder operation of the Web API. Once selected, click the ADD POLICY button to begin creating the policy from the template.

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5. The “<inbound>” policy section is applied to the incoming request before forwarding the request to the backend service. This is where we will check the cache for the authorisation token and if no hit, then we call the OAuth token endpoint to obtain a token.

   1: <inbound>

   2:     <cache-lookup-value key="token-{{Dev-Web1-ClientId}}" variable-name="bearerToken" />

   3:     <choose>

   4:         <when condition="@(!context.Variables.ContainsKey("bearerToken"))">

   5:             <send-request mode="new" response-variable-name="oauthResponse" timeout="20" ignore-error="false">

   6:                 <set-url>https://login.microsoftonline.com/xxxxxx.onmicrosoft.com/oauth2/token</set-url>

   7:                 <set-method>POST</set-method>

   8:                 <set-header name="Content-Type" exists-action="override">

   9:                     <value>application/x-www-form-urlencoded</value>

  10:                     <!-- for multiple headers with the same name add additional value elements -->

  11:                 </set-header>

  12:                 <set-body>@("grant_type=client_credentials&client_id={{Dev-Web1-ClientId}}&client_secret={{Dev-Web1-ClientSecret}}&resource=https%3A%2F%2Fxxxx.xxxxx.ax.dynamics.com")</set-body>

  13:             </send-request>

  14:             <set-variable name="accessToken" value="@((string)((IResponse)context.Variables["oauthResponse"]).Body.As<JObject>()["access_token"])" />

  15:             <!-- Store result in cache -->

  16:             <cache-store-value key="token-{{Dev-Web1-ClientId}}" value="@((string)context.Variables["AccessToken"])" duration="3600" />

  17:         </when>

  18:     </choose>

  19: </inbound>

Lets go through the key points of this definition below.

  • Line 2: – Assigns the value in cache to the context variable called “bearerToken”. On first entry, the cache value will be null and the variable will not be created. Note I am adding the ClientId as part of the cache key name to keep it unique. Property values are accessed by surrounding the key name with double braces. eg  {{myPropertyName}}
  • Line 4: – Checks if the context variable collection contains a key called “bearerToken” and if not found executes the code between the opening and closing “<when>” XML elements.
  • Line 5: – Initiates the request to the OAuth endpoint with a response timeout of 20 seconds. This will put the response message into the variable called “oauthResponse”
  • Line 6: – Is where you set the URL to send the request to. In this scenario I am using the Azure AD OAuth token endpoint below as our STS service: https://login.microsoftonline.com/xxxxxx.onmicrosoft.com/oauth2/token
  • Line 12: – This is where you define the body payload for the request and this is defined  as a typical client credentials grant type payload. Here I am getting the values for the client Id and secret from the user definable properties set in the Properties page. The resource parameter is just hardcoded to the Urlencoded resource URL of the API but can also parameterised.

<set-body>@(“grant_type=client_credentials&client_id={{Dev-Web1-ClientId}}&client_secret={{Dev-Web1-ClientSecret}}&resource=https%3A%2F%2Fxxxx.xxxxx.ax.dynamics.com”)</set-body>

  • Line 14: – Casts the response as a JSON object to allow the retrieval of the “access_token” value using an indexer and assigns it to the context variable “accessToken”.
  • Line 16: – Is where we add the contents of the variable “accessToken” into cache for a period of 3600 seconds.

6. Now that the “<inbound>” section has been completed, we can look at the “<backend>” section of the policy. This is where the policy forwards your request to the backend web service as defined in the API configuration page.

   1: <backend>

   2:     <send-request mode="copy" response-variable-name="transferWSResponse" timeout="20" ignore-error="false">

   3:         <set-method>POST</set-method>

   4:         <set-header name="Authorization" exists-action="override">

   5:             <value>@("Bearer " + (string)context.Variables["bearerToken"])</value>

   6:         </set-header>

   7:         <set-header name="Ocp-Apim-Subscription-Key" exists-action="delete" />

   8:         <set-header name="Content-Type" exists-action="override">

   9:             <value>application/json</value>

  10:         </set-header>

  11:     </send-request>

  12: </backend>

Lets go through this section as before.

  • Line 2: – Creates the request to the backend web service. Here we are placing the response from the web service into the variable called “transferWSResponse”.
  • Line 4: – Is the creating the “Authorization” header to be sent with the request.
  • Line 5: – Adds the bearer token value from the context variable “bearerToken” the authorisation header.
  • Line 7: – Removes the APIM subscription from being forwarded to the backend web service.

7. Now we need to return the response message from the backend web service to the caller. This is done in the “<outbound>” policy section. Here we just simply return the value of the variable “transferWSResponse” back to the caller.

   1: <outbound>

   2:     <return-response response-variable-name="transferWSResponse">

   3:     </return-response>

   4:     <base />

   5: </outbound>

That’s the whole policy defined which will call the OAuth endpoint the get the token and cache it for subsequent calls. 

Using the tracing feature in APIM, when the first request is made, the cache will be null and the variable will not be set as shown below.

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The next trace shows any subsequent requests will hit the cache and set the context variable to the bearer token until it expires.

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One important note about retrieving data from cache is its an out-of-process call and can add tens of milliseconds onto a request.

Working with the APIM polices can make a huge impact on your API development efforts as logging and access management can be off-loaded using the polices available in APIM. A full list of expressions used in polices can be found here: https://docs.microsoft.com/en-us/azure/api-management/api-management-policy-expressions

Enjoy…

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APIM backup & restore using Azure Automation Services

In this post I will describe the steps of using PowerShell scripts to backup APIM and using the Automation service to schedule the backup every month. The restore function also allows you to restore  APIM into another resource group or APIM service. For the project I am working on now, this is what I am doing to move the configuration settings between each environment.

First you need to create a blob store which ideally should be Read-Access geo-redundant storage (RA-GRS). This is where the APIM backups will be stored. After the blob store has been provisioned, create a container for the backup file as shown below.

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Once the container is created, take note of the Storage account name and Access key for the blob store. These values will be used in the PowerShell script later.

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Next provision an Azure Automation service and ensure the Create Azure Run As account is set to “yes”.

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Once it has been provisioned, ensure the modules have been updated by clicking on the “Modules” link on the left hand navigation panel and then “Update Azure Modules”. Note this does take a while to complete.

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After the update has been completed, click the “Browse gallery” link and in search textbox type “apim”. Once found,  double click on the row to open the import blade.

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Now click the Import icon to import the cmdlet. This can take several minutes to import.

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After the PowerShell module has been imported, create a new Runbook and ensure the type has been set to “PowerShell”. Then click the Create button at the bottom of the page.

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This will open up a new blade where we can add and test the PowerShell script to backup the APIM settings.

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Now add the following script below into the text editor and remember to update the variables with your environment settings. Once you have added the script, click the “Save” button and then the “Test pane” button to ensure the script runs successfully.

   1: Disable-AzureDataCollection

   2: Write-Output "Starting backup of APIM..."

   3:  

   4: # sign in non-interactively using the service principal

   5: $connectionName = "AzureRunAsConnection";

   6: $storageAccountName = "apimstorebackup";

   7: $storageAccountKey = "<storage account key>";

   8: $resourceGroupName = "APIMService";

   9: $apimName = "apimmanager"; 

  10: $targetContainerName = "backup";

  11: $targetBlobName "AzureAPIM.apimbackup"

  12: try

  13: {

  14:     # Get the connection "AzureRunAsConnection "

  15:     $servicePrincipalConnection=Get-AutomationConnection -Name $connectionName         

  16:  

  17:     Write-Output "Logging in to Azure..."

  18:     Add-AzureRmAccount `

  19:         -ServicePrincipal `

  20:         -TenantId $servicePrincipalConnection.TenantId `

  21:         -ApplicationId $servicePrincipalConnection.ApplicationId `

  22:         -CertificateThumbprint $servicePrincipalConnection.CertificateThumbprint 

  23: }

  24: catch {

  25:     if (!$servicePrincipalConnection)

  26:     {

  27:         $ErrorMessage = "Connection $connectionName not found."

  28:         throw $ErrorMessage

  29:     } else{

  30:         Write-Error -Message $_.Exception

  31:         throw $_.Exception

  32:     }

  33: }

  34:  

  35: $sourceContext = (New-AzureStorageContext -StorageAccountName $storageAccountName  -StorageAccountKey $storageAccountKey);

  36:  

  37: Write-Output "Starting backup of APIM instance";

  38: Backup-AzureRmApiManagement `

  39:             -ResourceGroupName $resourceGroupName `

  40:             -Name $apimName `

  41:             -StorageContext $sourceContext `

  42:             -TargetContainerName $targetContainerName `

  43:             -TargetBlobName $targetBlobName;

  44:  

  45: Write-Output "Backup of APIM completed.";

Here are the description of the variables:

  • $connectionName = “AzureRunAsConnection” – this is the default connection account that was created when the Automation service was provisioned.
  • $storageAccountName = “apimstorebackup” – name of the blob storage account that was created in the first step.
  • $storageAccountKey = “<storage account key>” – the blob store access key obtained from the portal.
  • $resourceGroupName = “APIMService” –  name of the Azure resource group.
  • $apimName = “apimmanager” – the name of the APIM service.
  • $targetContainerName = “backup”  – name of the backup container in blob store.
  • $tartgetBlobName = “AzureAPIM.apimbackup” – file name of the backup file.  This can be omitted and will create a default filename {apimName}-{yyyy-MM-dd-HH-mm}.apimbackup

Once you have confirmed the script executes without any errors, you can now set up a recurring schedule by creating a new schedule in the Automation service blade under Shared Resources.

imageimage

Next you need to link your Runbook to this schedule by double clicking on your runbook name and then the schedule button on the top menu. This will open another blade where you can view all your schedules that you can select from.

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That is the automated back process completed now. Below is the PowerShell script required to restored the backup file.

#get the storgae context
$sourceContext = (New-AzureStorageContext `
                    -StorageAccountName “<blob storage name>” `
                    -StorageAccountKey “<blob storage account key from Azure portal>”)

#restore the backup
Restore-AzureRmApiManagement -ResourceGroupName “<name of resource group>” `
                             -Name “<name of the APIM service>” `
                             -StorageContext $sourceContext  `
                             -SourceContainerName “<blob storage container name>” `
                             -SourceBlobName “<backup file name>”

More details on these scripts can be found here: https://docs.microsoft.com/en-us/powershell/module/azurerm.apimanagement/restore-azurermapimanagement?view=azurermps-4.3.1

Enjoy.

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Enforcing Ordered Delivery using Azure Logic Apps and Service Bus

When consuming messages from an Azure service bus the order may not be guaranteed due to the brokered based messaging scheme where multiple consumers can consume messages from the bus. Sure you can force the Logic App to execute as a single instance but then you sacrifice performance and scalability. You can also use ReceiveAndDelete but then you loose the transactional nature of the bus. Ultimately to ensure a message is consumed in the correct order using the transactional nature of the bus you would add a sequence number to each message and use this to enforce the ordering.

To achieve ordered delivery using Logic Apps, you would need to ensure all related messages are consumed by the same Logic App instance and for this we use the session Id property on the service bus. Below is the full workflow process to force ordered delivery using Logic Apps and session Id’s on the service bus subscription.

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This scenario is based on a financial institution which requires all monetary transfers to be processed in an ordered fashion.  The key is choosing a suitable session identifier and with this in mind, the account number was the most suitable candidate as we want a single consumer to process all the transactions for a particular account number.

Here we have created a subscription for a topic called AccountTransfers. Note the Enabled sessions is checked.

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Once the service bus has been configured, we can now dissect the workflow to see how we can achieve ordered delivery.

The workflow is initiated by a pooling Service Bus Connector. The properties of this connector are shown below. The key point here is to set the Session id to “Next Available”. This forces the Logic App to create a new instance for each unique session id value found on the service bus.

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The next action “ProcessSBMessage” is used to call another logic app which does the processing of the message found on the bus. Here I am just passing the raw base64 encoded message from the Service Bus Trigger action. Using the pattern “separation of concerns” moves the business logic  away from the process of ensuring ordered delivery.

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Once the message has been sent to the chained Logic App and a response has been returned, we can complete the message from bus with the following action.

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Next we go into a loop until the exit condition has been satisfied. I am going to use a counter that is incremented if no messages are found on the service bus. If no more messages are found on the service bus after 30 seconds, the loop will exit.

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The loop inside starts with another service bus connector trigger which gets the messages from the topic subscription. Here we only want to retrieve one message at a time from the service bus using a peek-lock trigger and using the Session Id from the initial service bus trigger “When a message is received in a topic subscription”.  We then check if a message is found in the output body using the expression “@not(equals(length(body(‘Get_messages_from_a_topic_subscription_(peek-lock)’)), 0))

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If a message is found, the “If True” branch is executed which again calls the same Logic App as before to process the message. Note the indexer to get to the context data as the service bus connector trigger above returns a collection.

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Once a successful response is received from the ProcessSBMessage Logic App, the message is completed and the LoopCounter variable is reset to zero. Note the lock token is from the service bus connector trigger within the loop and the Session Id is from the initial service bus connector which started the workflow. image

Below is the code view for setting the lockToken and SessionId of the “Complete the message” action inside the loop.  Take note of the indexer “[0]” before the LockToken element.

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If no messages are found on the service bus, the False branch is then executed. This simply has a delay action as not to pool too quickly and increments the LoopCounter. 

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The last step is to close the session when the Until loop exists using the Session Id from the initial service bus connector trigger which started the workflow.

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Now you are ready to the send messages into the service bus. You should see a Logic App spin up for each unique session Id. Remember to set the session Id property on the service bus to some value before sending the message.

Enjoy…

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Error updating AX entities using the Dynamics 365 for Operations connector in Logic Apps

When trying to update an entity via the Dynamics 365 connector you may encounter the following error.

{ “status”: 400, “message”: “Only 1 of 2 keys provided for lookup, provide keys for SalesOrderNumber,dataAreaId.”, “source”: “127.0.0.1” }

One would think passing the ItemInternalId guid value which is the primary key for the entity as the Object Id property would be adequate to find the record to update. Seems not by the error being thrown back.

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Apparently you need to supply the 2 keys,  SalesOrderNumber and dataAreaId  which was mentioned in the error response message as the Object Id as shown below. Note the comma between the sales order number (Sales Order) and the dataAreaId (Company)

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So the item path for the entity to update looking from the code view would look like this:

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Enjoy…

 

Posted in Azure, Logic Apps | 5 Comments

Fixing syntax errors when porting Logic Apps to Visual Studio

After initially designing your Logic App in the Azure Portal, you may wish to port it to Visual Studio 2017 to manage the template under a source control repository and to further develop it from Visual Studio.

After porting the code, you may encounter some of the following errors when trying to save or deploy your Logic App from Visual Studio.

Error: …the string character ‘@’ at position ‘0’ is not expected.

This is fairly easy to identity as Visual Studio highlights the code which it thinks the syntax is incorrect as shown below. Remember this code was ported over from the Azure Portal where it parsed without any issues.

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It is complaining about the unrecognised function . To get around this issue we need to use the “concat” string function to treat this as a string literal.

The original syntax is here: “ProductCodes”: “[@{outputs(‘Compose_Product_Detail’)}]”

By surrounding the whole value “[@{outputs(‘Compose_Product_Detail’)}]” with concat as shown below resolves this error.

“@concat(‘[‘, outputs(‘Compose_Product_Detail’)’, ‘]’)”

Breaking the designer when parameterising the subscription Id when calling a function

You may have a call-back function defined in your Logic App which has the subscription guid embedded in the code (blanked out for security reasons) similar to below:

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When trying to parameterise the subscription key by simply adding the function “subscription().subscriptionId” in place of the guid value as shown below:

“function”: {
“id”: “/subscriptions/subscription().subscriptionId/resourceGroup…

You will get the following error when trying to same the changes.

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To overcome this issue, wrap the value in a concat function as shown below. Note the url has been shorted with “…” to make it readable.

“function”: {
“id”: “[concat(‘/subscriptions/’,subscription().subscriptionId,’/resourceGroups/…/providers/Microsoft.Web/sites/…/functions/Cmn_GuidMapNullValue’)]”

You can also apply this same technique to parameterise other information in the Id key such as the website location.

Enjoy…

Posted in Azure, Logic Apps | Leave a comment

Robust Cloud Integration with Azure

For the last year I have been busy co-authoring this book on Azure Cloud Integration with my follow co-authors Abhishek Kumarm, Martin Abbott, Gyanendra Kumar Gautam, James Corbould and Ashish Bhanbhani.

Image result for robust cloud integration with azure

It is available on the Packt website here: https://www.packtpub.com/virtualization-and-cloud/robust-cloud-integration-azure

This book will teach you how to design and implement cloud integration using Microsoft Azure. It starts by showing you how to build, deploy, and secure the API app. Next, it introduces you to Logic Apps and helps you quickly start building your integration applications. We’ll then go through the different connectors available for Logic Apps to build your automated business process workflow. Its packed with a lot of information spanning just under 700 pages.

Don’t forget to check out another publication I co-authored back in 2015 with with Mark Brimble, Johann Cooper and Colin Dijkgraaf called SOA Patterns with BizTalk Server 2013 and Microsoft Azure.

SOA Patterns with BizTalk Server 2013 and Microsoft Azure - Second Edition Book Cover

And it is still available from the Packt website here: https://www.packtpub.com/networking-and-servers/soa-patterns-biztalk-server-2013-second-edition

Hope you enjoy reading it, just as I enjoyed writing the content.

Posted in Azure, Biztalk, Logic Apps, Web API | Tagged , , , | Leave a comment

Searching through messages in Logic Apps

Unfortunately Logic Apps do not provide an easy option to view the contents of a message unless you go through each log entry and view the outputs as shown below.

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However there is an alternative method using Log Analytics which comes with Operations Management Suite (OMS). By using Log Search you can search for specific property values within your messages. Below is an example of searching through the diagnostics log of a Logic App for a particular JobId and the results using OMS.

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To start using this feature we need to setup OMS first using the steps below.

1. In the Marketplace search for “Log Analytics” and select.

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2. Create the OMS Workspace using a suitable name and resource group.

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3. Next we need to add a storage account for the Logic Apps to store diagnostic data. From the Marketplace, search for “Storage Account” and select it.

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Create the storage account by providing a name and leave the “Account kind” as “General purpose”.

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4. Once the storage account is created, we need to link this to the OMS Workspace. Click on the Log Analytics resource that was created in step 2 as shown below.

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In the properties blade, scroll down to the “Workspace Data Sources” and click on “Storage account logs”.

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Then click the plus sign to add a storage account. Choose the storage account you created previously.image

After you have chosen the storage account, select the “Data Type” and chose events. Then click “OK” at the bottom of the page.image

Now that all the plumbing has been configured we can turn our attention to the Logic App. For this example we are going to create a simple logic app that receives a purchase order and sends it to RequestBin and then returns a status code of OK.

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Here is an example of the purchase order we are going to post to the Logic App.

{
   "CustomerCode": "CUST1000",
   "Lines": [
      {
         "LineNo": 1,
         "Price": 68.25,
         "ProductCode": "PRD1100",
         "Qty": 1
      }
   ],
   "OrderNo": "1000",
   "Total": 68.25
}

Once we have created the logic app, select code view to add our custom tracked properties on an action. I want to be able to search for orders using either the OrderNo, CustomerCode or the Total order value.

To do this add the highlighted “trackedProperties” section to the action, specifying the attribute name to search on and the path in the message to obtain the value from.

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Now that the logic app has been created and saved, we need to turn on Diagnostics for this Logic App. Under the Monitoring section of the Logic App, click on Diagnostics and then Diagnostics Settings shown below.

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Set the “Status” to On and check the “Archive to a storage account”, select the storage account that was provisioned previously and the retention periods to what you require.

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Now check the  “Send to Log Analytics” and select the OMS Workspace created before. Then click the Save button.

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Everything should be good to go now. Use something like PostMan to start sending test messages to the Logic App. After a few minutes you should see the tracked properties and their values being written the blob store under the storage account and a container called “insights-logs-workflowruntime”

If you keep drilling down into the containers that matches your logic app name, you will see a file called “PT1H.json”. Inside the file you will see the entries for the tracked properties.

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To use OMS to search on on of your properties, click on the Log Analytics under your logic app.image

Once the blade opens click on the OMS Portal link which opens the portal site. On the portal site, click the icon “Get Started”. Then under “Data” and “Custom Fields” you should be able to see your custom tracked properties. Take note of these field names as these will be used in the search query.

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Now click the Search icon symbol on the left navigation pane and enter the following query “Type=AzureDiagnostics  resource_workflowName_s=Orders” into the search  box and then click search. Note it can take a few minutes before the data turns up in OMS if you just submitted a message to the logic app. The query will list all logics that have been triggered with the Logic App name called “Orders”.

You should get a list of all the triggers related to the “Orders” logic app as shown below. Here I found 118 events in the last day.image

You can narrow your search down further by modifying the search query. Searching for orders with an order number equal to 1004, you would enter this into the query field “Type=AzureDiagnostics  resource_workflowName_s=Orders trackedProperties_OrderNo_s=1004”.  This will display the records matching the order number.

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Also by left clicking on the ellipse (…)  next to each field brings up another context menu to provide more filtering options.

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In conclusion, by using OMS, it provides the ability to search for tracked properties, save common queries and create custom  dashboards. I encourage you to look at all the features available in OMS as we only touched the surface here in this post.

Enjoy.

Posted in Azure, Logic Apps | Tagged , , | 3 Comments