Getting Started with Logic Apps - Fundamentals | What is Logic App

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What is Logic App?

It is workflow, an orchestration in cloud (which is hosted on Microsoft Azure) with connections to systems, services.

Logic App is an Offering from Microsoft primarily to cater the need of integrating and designing business workflow/process with orchestrating the SAAS services. It also now extends to services which are on premises.

Logic App is one of the Service amongst the other Azure App Services (Web Apps, Mobile Apps, API Apps,Functions) and runs on top of Azure Service Fabric. 

Logic App is a fully managed iPaaS (integration Platform as a Service) solution which allows developers to build highly scalable workflows and will automatically scale to meet demand. 

In Layman term – Microsoft has provided a platform which is managed by them to enable a user to design/create a workflow which has a provision to connect services which are cloud based or also on premises (integrating various services) thus the name IPaas (integration Platform as a Service). 

You get a browser based designer (also available in visual studio), where you can design the workflow by selecting the appropriate Trigger (the way to start the workflow based on certain event ) thereafter adding new steps Action (it can be after a Condition) where you select the Connectors(the way to connect to data ,services or system). 

After you save the workflow, it gets deployed – ready to use. And you don’t have to worry about the load scenarios, it auto scales and you are charged only when it is executed (number of Actions).

Logic App is also marketed by Microsoft as Serverless, by serverless it doesn't mean there are no servers, it just means the developers do not have to worry about the underlying infrastructure (there is an Abstraction) instead they just have to focus on the business logic (faster development). 

The other two offerings under serverless are Azure Functions and Event Grid.

Although Logic App is said to be serverless, in reality there are servers/ virtual machine which host them but are hidden(no direct access) from users. 

And each region has some set of such VM's and thus there is range of IP addresses, which you can see in properties  -- Runtime outgoing IP Address, Connector outgoing IP address (outgoing  from Logic app) and Access endpoint IP address (incoming to Logic app). 

Logic Apps is based on the Workflow Definition Language and provides a way to simplify, automate and integrate scalable workflows into the cloud, WDL is based on following basic structure

So whatever you create in Logic app Designer gets converted in JSON. JSON is used to define the workflow based on WDL, and same can be seen in Code view in Portal or in Visual Studio.

Thus from development perspective- Logic app is nothing but JSON definition along with ARM Template and from runtime perspective - Logic apps is a Job Scheduler with a JSON based DSL describing a dependency graph of actions.

Building Blocks of Logic Apps

Trigger

Logic Apps always start from a trigger and then execute a series of steps. As in BizTalk Message creates instance of Orchestration likewise trigger creates an instance of Logic Apps.

Push, pull, repeating and manual are way to trigger Logic Apps

Push – This is reactive type, where the consumer notifies the workflow or creates an event to start the workflow(logic app endpoint).

Poll(pull) – This is proactive type, where the workflow polls a system or service for notification or event.(Service endpoint)

Repeating(Recurrence) – Prescribed Schedule to start the workflow

Manual – Manually starting the Workflow(You can click Run now button in Portal)

Connectors

In my perspective, the base of Logic Apps is connector – everything in logic apps is around connectors (All components are api apps). All connectors are technically API apps that uses a metadata format named swagger, REST as pluggable interfaces and JSOn as the data interchange format.

It can act as trigger and action, to connect with any service is via either  by Trigger or Action and both are api connections. In other words, connectors is encapsulation of authentication, data validation in combination of Triggers and Actions.

It is on same line as that of Adapters in BizTalk. And at the time of writing this post there are 200+ connectors available, and every week there is addition to it.

     1.Standard connectors
    This are pre-included and are available in Logic App and does not cost extra.

     2.Integration account connector

It comes at extra cost as these connectors become available when you create Integration Account. It enables us to deal with complex integration scenarios where maps, trading partners management etc are involved .

3.On premise connector(Hybrid connector)

     This are the connectors used for connecting to systems which are on premises,
     and this is done with the help of on-premise data gateway. For now connectors for DB2, Oracle DB, SQL Server, FileSystem and Sharepoint server, Informix, Websphere MQ etc are available.

    4.Enterprise connectors

 It comes at extra cost for Enterprise level systems like MQ and SAP.

    5.Custom connector

 If none of above connectors satisfy the need, then there is provision to create a custom connector just like we have provision in BizTalk to create custom Adapter.

Action

Every step  in Logic App (even trigger) is called Action (condition can be before it). Action always mapped to operation in Managed Connector or web api. 

Every action has input and output associated with it.

Output of particular action is available to all the actions following it and can be used by them e.g., Trigger's output is triggerbody and it is available to all actions (as trigger is first action in logic app).

Enterprise Integration Pack

Integration Account is required for Enterprise integration Pack. It enables to have BizTalk like power in cloud, where you get provision to store the artifacts (xsd, maps, trading partners, certificates, agreement etc) and use them to build Enterprise level B2B/EAI solution. 

It has supports for industry standard like AS2,EDI X12, EDIFACT , Flatfile, XML etc.

All the features around B2B/EAI solutions like validation, transformation, Encoding , decoding are made available through it enabling to have solutions build in Serverless fashion.

Read through examples of Enterprise Integration Pack

Getting Started with Logic Apps - XML to EDI X12
Getting Started with Logic Apps - EDI X12 Fundamentals
Getting Started with Logic Apps - Enterprise Application Integration

Flow controls

• Scope

         Logical grouping of actions

• Response

       For any request that comes in there can be response associated with it

• Condition

     Evaluates an expression and executes the corresponding result branch

• ForEach

     Will iterate over an array and perform inner actions for each item

• Until

     Will execute inner actions until  a condition results to true

• Switch Statement

     Only one branch will be executed corresponding to condition of the            particular   case

• Calling another Logic App (Nesting)

     Workflows can be nested by making a workflow exposing a  callable endpoints (can be reached over an url)

• Calling custom code via Azure function

     In a scenario where custom code is required to be executed, the code can be added as Azure function and can be called from Logic app

Read about calling Function App from logic app  -- Calling Active Directory Secured Function App from Logic Apps   and    Using Managed Identity in Logic Apps for Calling Active Directory Secured Function App

Security

Security in Logic app can be applied in various ways and on different levels like securing access to triggers, securing access to Run History, securing logic app editing etc.

Out of box we have provision of SAS(shared access signature) and restriction can be applied as to who all can call the logic app based on IP Addresses(IP Filtering), you can look at it at Settings->Access control configuration.

Azure Role Based Access Control  and Azure Resource Lock can be used to prevent accidental/intentional editing or deleting of the logic apps.

If you think above aren’t enough, then we have option to leverage the power of APIM where Azure Active Directory, certificate, OAuth, or other security standards can be used.

Read about securing logic app with APIM --  Securing Logic app with Active Directory 

Monitoring

For monitoring there is out of box feature which tracks and enables us to view the state of each logic app instance – Run history , it includes all the details like input and output of each step in the workflow. 

Through this we can check if workflow was successful or failed, how much time it took to complete, what was input received, what was the output, also exception details if there are any.

Also on same line we have tracking for Triggers – Trigger history which keeps state of triggers if they were successful, failed, skipped etc.

Apart from above two we can leverage  azure diagnositcs, api management, azure alerts for additional monitoring of Logic apps and implementing alert mechanism on top of it.

Read about Advanced Monitoring  - Getting Started with Logic Apps - What happened to the Request?

If you have questions or suggestions, feel free to do in comments section below !!!

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Learn More about Logic App

• How to configure Logic App Standard workflow behind Azure APIM
• How to Query Azure Table storage from Logic App | How to filter results of Azure Table storage from Logic App
• Understanding expressions in Logic Apps | Frequently used expressions in Logic Apps | What is expressions in Logic App
• How to use Logic app Run History | How to troubleshoot Logic App workflow execution
• Logic App and Slack - Sending messages to slack channel | Logic app and slack integration | Connecting Logic App to Slack channel
• How to access Application settings fields value from Logic app Standard workflow | Using Application settings as configuration store for Logic app standard workflow
• Developing Logic app standard workflow which uses Map locally  and deploying to Azure
• Developing Logic App Standard Workflow Using Visual Studio Code | Create Logic App Standard Workflow Using Visual Studio Code
• Logic App - Xml to Json using Liquid Map | Append in Liquid Map
• How to use Azure Event Grid Custom Topic | Publishing and Subscribing from Azure Event Grid Custom Topic using Logic App
• Using Azure Storage Account Table as Config Store  for Logic Apps | How to read and write from Logic App to Azure Storage Account Table
• Get Logic App Name in Logic App
• Difference between Logic App Consumption and Logic App Standard 
• Getting Started with Logic App Standard | Overview of Logic App Standard | Basics of Logic App Standard
• How to find count of Logic App executions using Azure Portal
• Azure Functions vs Azure Logic App | Difference between Azure Functions and Azure Logic App
• Getting started with Logic App : Liquid Map | Using Liquid template in Logic app
• How to get actual error message of Scope in Logic App | Exception Handling in Logic app
• Interview questions and answers on Logic Apps | Interview questions for azure logic app developers
• How to execute Stored Procedure in Logic App | How to connect to SQL in Logic App
• How to get current date in logic app | How to format date time in Logic App
• BizTalk Developer getting started with Logic App
• Getting Started with Logic Apps - Fundamentals
• Getting Started with Logic Apps - Enterprise Application Integration
• Getting Started with Logic Apps - AS2
• Getting Started with Logic Apps - EDI X12 Fundamentals
• Getting Started with Logic Apps - XML to EDI X12
• Getting Started with Logic Apps - EDI X12 to XML
• Getting Started with Logic Apps - What happened to the Request?
• Inserting Multiple Records In On Prem SQL Using Logic App
• Inserting data in On Premises SQL Database using Logic Apps
• Installing and Configuring On Premises Data Gateway - By adding user to Active Directory
• XML Batching(Aggregation) in Logic App
• Batching(Aggregating) messages in Logic App
• Debatching(Splitting) JSON Message in Logic Apps - ForEach and SplitOn
• Debatching(Splitting) XML Message in Logic Apps - ForEach and SplitOn
• Securing Logic App with Azure Active Directory authentication
• Removing ns0: prefix from xml output from BizTalk/Logic app XSLT map
• Using Managed Identity in Logic Apps for Calling Active Directory Secured Function App
• Logic Apps : Fetching ISA and GS Segment Values From Interchange Envelope and Mapping
• Logic Apps : For Each Inside a For Each - Fetching values from field in an array inside an array