Subscribing to Tweets using Azure Logic Apps

Code Sample
09/23/2019

A tutorial for using Azure Logic Apps to monitor recent tweets on Twitter. The app sends an email notification to subscribers when new tweets are posted matching a search term.

Technologies Used

Azure Logic Apps - Manage subscriptions, monitor tweets, and send email notifications to subscribers
Azure Table Storage - Store persistent data like subscriptions

Prerequisites

An Azure subscription
- If you don't have one, sign up for free.
- If you're a student, you can sign up for free without requiring a credit card at sign-up.
An email account (Office 365 or Outlook for all features, Gmail if approval emails are not required)
A Twitter account
A web browser
Azure Storage Explorer (optional, but recommended for working with Azure Table Storage)

Create Azure resources

Logics Apps allow you to build and test your application entirely from the Azure Portal using the Logic Apps Designer. Let's get started by creating a few Logic Apps and a storage account.

Go to the Azure portal and sign in with your Azure account credentials.

See Prerequisites for sign up links if you don't have an account

Create a Logic App to manage subscribers

From the main Azure menu, choose Create a resource > Web > Logic App.

Provide details about your Logic App as shown here. After you're done, choose Create.

Property	Value	Description
Name	TwitterSubscriptionManager	The name for your Logic App
Subscription	<your-Azure-subscription-name>	The name for your Azure subscription
Resource group	Create new > TwitterLogicAppSample	The name for the Azure resource group used to organize related resources
Location	East US	The region where your Logic App is hosted
Log Analytics	Off	Keep the Off setting for diagnostic logging.

Create a Logic App to monitor tweets and send notifications to subscribers

From the main Azure menu, choose Create a resource > Web > Logic App.

Provide details about your Logic App as shown here. After you're done, choose Create.

Property	Value	Description
Name	TwitterNotifier	The name for your Logic App
Subscription	<your-Azure-subscription-name>	The name for your Azure subscription
Resource group	Use existing > TwitterLogicAppSample	Use the same resource group as the Logic App
Location	East US	The region where your Logic App is hosted
Log Analytics	Off	Keep the Off setting for diagnostic logging.

Create a Storage Account

From the main Azure menu, choose Create a resource > Storage > Storage account - blob, file, table, queue.

Provide details about your Storage Account as shown here. After you're done, choose Create.

Property	Value	Description
Name	<your-name>twitterdata	The name for your Storage Account
Deployment model	Resource manager	Use Resource Manager for new applications and for the latest Azure features
Account kind	Storage (general purpose v1)	The type of storage account. V1 has everything we need but you can use V2 if you like.
Location	East US	The region where your app's data is hosted
Replication	Locally-redundant storage (LRS)	The least durable but lowest cost storage
Performance	Standard	Standard storage accounts are backed by magnetic drives and provide the lowest cost per GB
Secure transfer required	Enabled	There's no reason not to use HTTPS
Subscription	<your-Azure-subscription-name>	The name for your Azure subscription
Resource group	Use existing > TwitterLogicAppSample	Use the same resource group as the Logic App
Log Analytics	Off	Keep the Off setting for diagnostic logging.

Create a table in the storage account

Azure Table Storage will be used to persist data about subscribers and tweets between executions of the Logic App.

From the main Azure menu, choose Resource groups > TwitterLogicAppSample.
Choose the <your-name>twitterdata Storage Account that was created earlier.
The storage account overview will open. Under Services choose Tables.
Click the + Table button at the top to add a new table named subscriptions and choose OK.

Configure the TwitterSubscriptionManager Logic App

This Logic App will accept subscribe and unsubscribe requests from users to/from a Twitter search term of their choosing. It will also verify the request was intentional by sending a verification email to the user prior to honoring their request.

Logic App Designer view of the final TwitterSubscriptionManager Logic App

Configure the trigger for the TwitterSubscriptionManager Logic App

Every Logic App must start with a trigger, which fires when a specific event happens or when a specific condition is met. Each time the trigger fires, the Logic Apps engine creates a Logic App instance that starts and runs your workflow.

From the main Azure menu, choose Resource groups > TwitterLogicAppSample.
Choose the TwitterSubscriptionManager Logic App that was created earlier.
The Logic Apps Designer will open and show a page with an introduction video and commonly used triggers. Under Start with a common trigger, choose When a HTTP request is received.
Use the Save button at the top of the screen to save the Logic App. Notice that a unique URL to trigger your Logic App was populated in the HTTP POST URL box. Your Logic App workflow will be triggered when a POST request is received at this URL.

Configure the parameters for the HTTP trigger

Your Logic App will need some information from the user to subscribe/unsubscribe them to/from a Twitter search term or hashtag. Namely, we'll need the email address of the subscriber, the search term, and whether the request is to subscribe or unsubscribe.

In the When a HTTP request is received trigger, click the Edit link next to Using the default values for the parameters. In the box that appears, we'll provide a JSON schema of the request format our Logic App should expect.
1. Under the Request Body JSON Schema box, click the Use sample payload to generate schema link.
2. In the Enter or paste a sample JSON payload dialog, paste the JSON below.
```
{
  "action": "subscribe",
  "email": "example@example.com",
  "term": "#microsoft"
}
```
3. Choose Done.
Save the Logic App.

Send an approval email to validate the request

Choose + New step in the Logic Apps Designer.
Under Choose an action, enter "send approval email" as your filter. From the actions list, select the Send approval email action for the email provider that you want.
1. To filter the actions list to a specific app or service, you can select that app or service first:
  - For personal Microsoft accounts, select Outlook.com.
  - For Office 365 work or school accounts, select Office 365 Outlook.
  The Gmail service does not support sending approval emails. If you only have a Gmail account, you can still use the Send an email action but your Logic App will not be able to receive responses to the email.
If asked for credentials, sign in to your email account so that Logic Apps can create a connection to your email account.
In the Send approval email action, specify the data that you want the email to include.
1. Click inside the To box. The dynamic content dialog will appear. Choose email from the Dynamic content tab under the When a HTTP request is received heading. This will use the email address provided in the body of the HTTP request that triggered the workflow.
2. If you like, edit the Subject of the email. You can include other parameters from the HTTP request using the dynamic content dialog. For example, you may want to change the subject to "Please approve <action> request for notifications about <term> tweets" where the <action> and <term> strings are replaced with the parameter values from the HTTP request.
Save the Logic App.

Check if the request was approved

After the approval email is sent, the Logic App will wait for the user to click either the "Approve" or "Reject" link in the email. Once the user clicks one of those links, the Logic App will need to determine what to do next based on the response.

Choose + New step in the Logic Apps Designer.
Under Choose an action, enter "condition" as your filter. From the actions list, choose the Condition Control action.
In the Condition action, populate the tree of conditions to evaluate.
1. Leave the And drop down as is.
2. Click inside the Choose a value box. The dynamic content dialog will appear. Choose SelectedOption from the Dynamic content tab under the Send approval email heading.
3. Leave the value of the is equal to condition unchanged.
4. In the Choose a value box, enter Approve.
Save the Logic App.

Check if the request was for subscribing or unsubscribing

Once the request is approved the Logic App will need to perform the requested action (subscribe or unsubscribe the user). In this step, we'll determine which action to perform.

Choose Add an action within the If true block below the Condition in the Logic Apps Designer.
Under Choose an action, enter "switch" as your filter. From the actions list, choose the Switch Control action.
In the Switch action, populate the On value to tell the control action what value should be used to determine the next step.
1. Click inside the On box. The dynamic content dialog will appear. Choose action from the Dynamic content tab under the When a HTTP request is received heading.
Below the Switch action, locate the Case block. Populate the Equals box with the text subscribe.
Click the (+) button between the Case block and the Default block. A Case 2 block will be added.
Inside the Case 2 block, populate the Equals box with the text unsubscribe.

If you like, you can rename these case blocks using the Rename option within the ··· menu of each block.
Save the Logic App.

Choose Add an action within the Case block containing "Equals subscribe."
Under Choose an action, enter "insert or replace" as your filter. From the actions list, choose the Insert or Replace Entity Azure Table Storage action.
In the Insert or Replace Entity action, specify the table and the entity to insert or replace.
1. You may be prompted for a Storage Account connection
  1. In the Connection Name box, provide a name like TwitterLogicAppStorage.
  2. Choose the Storage Account created earlier, <your-name>twitterdata.
  3. Click Create.
2. Once the connection is created, choose subscriptions from the Table drop down.
3. Click inside the Partition Key box. The dynamic content dialog will appear. Switch to the Expression tab and enter uriComponent(toLower(triggerBody()['email'])) into the expression box. Click OK to set the expression as the partition key value.
  
  This expression converts the email field from the POST request to lower case and then URI-encodes it. Converting to lower case will ensure that the user can unsubscribe easily later without the need to use the exact casing as when they subscribed. The encoding is necessary in case the user enters a character that is not permitted in partition keys or row keys, such as #.
4. Click inside the Row Key box. The dynamic content dialog will appear. Switch to the Expression tab and enter uriComponent(toLower(triggerBody()['term'])) into the expression box. Click OK to set the expression as the row key value.
5. In the Entity box, enter the JSON below.
```
{
  "LastTweetId": ""
}
```
  The LastTweetId property will be used to track the most recent tweet our Logic App found that matches the provided search term. It will simplify determining which tweets are "new" later.
Save the Logic App.

You can read more about partition keys, row keys, and Azure Table Storage in general here.

Remove an entry from the subscriptions table if the request was to unsubscribe

Choose Add an action within the Case 2 block containing "Equals unsubscribe."
Under Choose an action, enter "delete entity" as your filter. From the actions list, choose the Delete Entity Azure Table Storage action.
In the Delete Entity action, specify the table and the entity to delete.
1. Choose subscriptions from the Table drop down.
2. Click inside the Partition Key box. The dynamic content dialog will appear. Switch to the Expression tab and enter uriComponent(toLower(triggerBody()['email'])) into the expression box. Click OK to set the expression as the partition key value.
3. Click inside the Row Key box. The dynamic content dialog will appear. Switch to the Expression tab and enter uriComponent(toLower(triggerBody()['term'])) into the expression box. Click OK to set the expression as the row key value.
4. Leave the ETag box empty.
Save the Logic App.

Test out the TwitterSubscriptionManager Logic App

Congratulations! The Logic App should now be ready for use. Let's test it out!

Save any outstanding changes made to the Logic App using the Save button at the top of the Logic Apps Designer.
Click the When a HTTP request is received trigger to expand it. Copy the value of the HTTP POST URL using the Copy URL button. Store this for later use.

Make a HTTP POST request to the URL copied in the last step.

On Windows, this can be done using a PowerShell command like this:

Invoke-RestMethod -Method Post -Body (@{ "action" = "subscribe"; "email" = "example@example.com"; "term" = "#azure" } | ConvertTo-Json) -ContentType "application/json" -Uri "the-url-of-your-logic-app"

On Mac/Linux/Windows Subsystem for Linux, this can be done using a cURL command like this:

curl --request POST --data '{"action":"subscribe","email":"example@example.com","term":"logic apps"}' --header "Content-Type: application/json" "the-url-of-your-logic-app"

Close the Logic Apps Designer using the X in the top right corner of the blade.
Choose Refresh at the top of the Logic App overview blade.
Under the Run history section of the Logic App overview blade, find the most recent run of the Logic App. Click its row to view a visualization of the executed workflow.
Optionally, use Azure Storage Explorer to browse to the <your-name>twitterdata Storage Account and verify an entity was added to the subscriptions table.

Configure the TwitterNotifier Logic App

This Logic App will periodically query tweets from a Twitter search API based on the subscriptions in the Azure Table and inform subscribers of new tweets via email.

Logic App Designer view of the final TwitterNotifier Logic App

Configure the trigger for the TwitterNotifier Logic App

This Logic App's trigger will be a recurrence, meaning the Logic App will execute itself automatically based on a configurable time interval.

From the main Azure menu, choose Resource groups > TwitterLogicAppSample.
Choose the TwitterNotifier Logic App that was created earlier.
The Logic Apps Designer will open and show a page with an introduction video and commonly used triggers. Under Start with a common trigger, choose Recurrence.
Keep the default recurrence frequency or update it if you like.
Use the Save button at the top of the screen to save the Logic App. If you chose a frequent interval for the Logic App, you may wish to return to the Logic App's overview blade and disable the Logic App until it is complete.

Read subscriptions from the Table Storage

Choose + New step in the Logic Apps Designer.
Under Choose an action, enter "get entities" as your filter. From the actions list, select the Get entities Azure Table Storage action.
In the Get entities action, specify the details of subscriptions table created earlier.
1. You may be prompted for a Storage Account connection
  1. In the Connection Name box, provide a name like TwitterLogicAppStorage.
  2. Choose the Storage Account created earlier, <your-name>twitterdata.
  3. Click Create.
2. Once the connection is created, choose subscriptions from the Table drop down.
Save the Logic App.

Select the subscription details from the entities

Next well map each Table Storage entity to an object with more convenient property names and URI-decoded versions of the partition key and row key.

Choose + New step in the Logic Apps Designer.
Under Choose an action, enter "select" as your filter. From the actions list, choose the Select Data Operations action.

In the Select action, specify the properties to select from the table entities.

Click inside the From box. The dynamic content dialog will appear. Choose Get entities result List of Entities from the Dynamic content tab.

In the Map fields, enter the following mappings

Key	Value	Details
Email Encoded	Get entities result An entity Partition Key	Choose this value from the Dynamic content tab
Search Term Encoded	Get entities result An entity Row Key	Choose this value from the Dynamic content tab
Email	`uriComponentToString(item()['PartitionKey'])`	Enter this value into the Expression tab of the Dynamic content dialog
Search Term	`uriComponentToString(item()['RowKey'])`	Enter this value into the Expression tab of the Dynamic content dialog
Last Tweet ID	`item()['LastTweetId']`	Enter this value into the Expression tab of the Dynamic content dialog

The item() portion of the expression is a function that returns the item that is in the current iteration of a repeating action. It may be helpful to think of this as the element at the current index of a loop over an array.

Save the Logic App.

Create a loop to iterate through the subscription objects

Choose + New step in the Logic Apps Designer.
Under Choose an action, enter "for each" as your filter. From the actions list, choose the For each Control action.
In the For each action, specify the output of the Select action as the value for the Select an output from previous steps box. Click within the box and choose Output under the Select step header of the Dynamic content tab.
Save the Logic App.

Get recent tweets from the Twitter "Search tweets" API

Twitter offers an API that provides the most recent tweets matching a search term (word, phrase, or hashtag). We'll query that API for each subscribed search term within our Logic App. The API is available as a Microsoft Connector. A connector is a proxy or a wrapper around an API that allows the underlying service to talk to Microsoft Flow, PowerApps, and Logic Apps. You can read more about the Twitter Connector here.

Choose Add an action within the For each loop in the Logic Apps Designer.
Under Choose an action, enter "search tweets" as your filter. From the actions list, choose the Search tweets Twitter action.
If asked for credentials, sign in to your Twitter account so that Logic Apps can create a connection and call the Twitter API.
In the Search tweets action, specify the properties of the API request.
1. Click within the Search text box. The dynamic content dialog will appear. Switch to the Expression tab and enter item()['Search Term'] into the expression box. Click OK to save the expression.
2. Click the Show advanced options link within the Search tweets action.
3. If you wish, increase the Maximum results to 100.
4. Click within the sinceId box. The dynamic content dialog will appear. Switch to the Expression tab and enter item()['Last Tweet ID'] into the expression box. Click OK to save the expression.
  
  This will ask the Twitter API to only return tweets that were created after the specified tweet ID.
Save the Logic App.

Check if there are new tweets matching the search term

We want to check if any new tweets matching the search term have been posted since the last time our Logic App executed. Since we asked the Twitter API to only return tweets since the last tweet ID our Logic App encountered, we can check the number of tweets returned by the API to determine if we should notify the subscriber of new tweets.

Choose Add an action within the For each loop in the Logic Apps Designer.
Under Choose an action, enter "condition" as your filter. From the actions list, choose the Condition Control action.
In the Condition action, populate the tree of conditions to evaluate.
1. Leave the And drop down as is.
2. Click inside the first Choose a value box. The dynamic content dialog will appear. Switch to the Expression tab and enter length(body('Search_tweets')) into the expression box. Click OK to save the expression.
  
  This expression will return the number of tweets in the body of the Twitter API response.
3. Change the value of the is equal to condition to is greater than.
4. In the Choose a value box, enter 0.
Save the Logic App.

Update the Last Tweet ID for the subscription in Azure Table Storage

Choose Add an action within the If true block below the Condition in the Logic Apps Designer.
Under Choose an action, enter "merge entity" as your filter. From the actions list, choose the Merge Entity Azure Table Storage action.
In the Merge Entity action, specify the table entity to update.
1. In the Table box, choose subscriptions from the drop down.
2. Click inside the Partition Key box. The dynamic content dialog will appear. Switch to the Expression tab and enter item()['Email Encoded'] into the expression box. Click OK to save the expression.
3. Click inside the Row Key box. The dynamic content dialog will appear. Switch to the Expression tab and enter item()['Search Term Encoded'] into the expression box. Click OK to save the expression.
4. In the Entity box, enter the JSON template below.
```
{
  "LastTweetId": <id>
}
```
  1. After populating the field, highlight the <id> portion of the field's value and delete it.
  2. With your cursor at the position where <id> used to be, click the Expression tab in the Dynamic content dialog.
  3. In the expression box, enter first(body('Search_tweets'))['TweetId'] and choose OK. This will update the ID of the most recent tweet in the table entity.
5. In the ETag box, enter *. This will update the table entity regardless of whether it has changed since we queried it.
Save the Logic App.

Send a notification email if there are new tweets matching the subscribed term

Choose Add an action within the If true block below the Merge Entity action in the Logic Apps Designer.
Under Choose an action, enter "send an email" as your filter. From the actions list, select the Send an email action for the email provider that you want.
1. To filter the actions list to a specific app or service, you can select that app or service first:
  - For personal Microsoft accounts, select Outlook.com.
  - For Office 365 work or school accounts, select Office 365 Outlook.
  - For personal Google accounts, select Gmail.
If asked for credentials, sign in to your email account so that Logic Apps can create a connection to your email account.
In the Send an email action, specify the data that you want the email to include.
1. Click inside the To box. The dynamic content dialog will appear. Switch to the Expression tab and enter item()['Email'] into the expression box. Click OK to save the expression.
2. In the Subject box, enter the value <number> new tweets matching <term>.
  1. After populating the field, highlight the <number> portion of the field's value and delete it.
  2. With your cursor at the position where <number> used to be, click the Expression tab in the Dynamic content dialog.
  3. In the expression box, enter length(body('Search_tweets')) and choose OK. This will insert the number of new tweets into the subject at the correct position.
  4. Now highlight the <term> portion of the field's value and delete it.
  5. With your cursor at the position where <term> used to be, click the Expression tab in the Dynamic content dialog.
  6. In the expression box, enter item()['Search Term'] and choose OK. This will insert the subscribed search term into the subject at the correct position.
  OPTIONAL To be grammatically correct, we should make the word "tweets" singular if the number of new tweets is 1. If you like, replace the word "tweets" with this expression: if(equals(length(body('Search_tweets')), 1), 'Tweet', 'Tweets').
3. In the Body box, enter any value you like. If you don't want to include anything, just enter a space.
  1. If you would like to include the content of the most recent tweet, click within the Body box and enter any explanatory text along with the expression first(body('Search_tweets'))['TweetText'] via the dynamic content dialog.
    
    If you would like to include other properties of the most recent tweet in the email body, refer to the list of property paths available in the TweetModel. Simply replace TweetText in the expression with one of the other property paths, such as TweetedBy.
Save the Logic App.

Test out the TwitterNotifier Logic App