Azure Functions Cheatsheets
Azure Functions Cheatsheets
By Saeed Salehi
4 min read
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Part of series
Developing Solutions for Microsoft Azure (AZ-204) certification exam Cheatsheets
- Part 1:
Introduction to (AZ-204) certification exam Cheatsheets
- Part 2:
Implement IaaS in Azure Cheatsheets
- Part 3:
Azure Functions Cheatsheets
- Part 4:
Azure App Service Cheatsheets
- Part 5:
Develop solutions that use Blob storage Cheatsheets
- Part 6:
Develop solutions that use Azure Cosmos DB Cheatsheets
- Part 7:
Implement Azure Security Cheatsheet
- Part 8:
Microsoft Identity platform Cheatsheet
- Part 9:
Monitoring And logging in Azure Cheatsheets
- Part 10:
Azure Cache for Redis Cheatsheets
- Part 11:
Develop message-based solutions Cheatsheets
- Part 12:
Develop event-based solutions Cheatsheets
- Part 13:
API Management in Azure Cheatsheets
Azure Functions lets you develop serverless applications on Microsoft Azure requires general Azure Storage Account
- Azure Blob
- Queue
- Files and Table storage.
Difference with Azure Logic Apps
For Azure Functions, you develop orchestrations by writing code and using the Durable Functions extension. For Logic Apps, you create orchestrations by using a GUI or editing configuration files (workflow).
Logic Apps
- Logic App code View: extend definitions you use Logic App code View
- Integrate the workflow: Enterprise Integration Pack (EIP)
Hosting Plans
- Consumption plan: Default, only pay for compute resources when your functions are running (1.5 GB or memory / 1 CPU )
- Premium plan: pre-warmed workers
- Dedicated plan: run your function within a AppService - price can be predictive, Best for long-running (Always on should be enabled!)
Deployment
- AppService Environment (ASE)
- Kubernetes (KEDA)
Scaling
scale controller to monitor the rate of events (scale out / in) latency of scaling from zero to one - cold start
Scaling behaviors
- Maximum instances: 200
- New instance rate: new instances allocated HTTP: once per second / Non-Http: once on every 30 seconds
limit scale out by setting functionAppScaleLimit
parameter to 0 / null or a valid number
Each function contains:
- Code
- Config (function.json)
Code should be placed in Root and root folder should contains a host.json file contains runtime-specific configuration
triggers and bindings
Trigger: what cause a function to run. must have exactly 1 trigger!
Binding: way of connecting another resource (input bindings, output bindings, or both)
Sample
{
"bindings": [
{
"type": "queueTrigger",
"direction": "in",
"name": "order",
"queueName": "myqueue-items",
"connection": "MY_STORAGE_ACCT_APP_SETTING"
},
{
"type": "table",
"direction": "out",
"name": "$return",
"tableName": "outTable",
"connection": "MY_TABLE_STORAGE_ACCT_APP_SETTING"
}
]
}
Types of binding expressions (path
parameter in function.json
)
- app settings (
% sign
)- The
connection
property of triggers and bindings is a special case and automatically resolves values as app settings, without percent signs.
- The
- filename
{filename}
- Trigger metadata
- JSON payloads
- Dot notation
- Create GUIDs
{rand-guid}
- Current time
{DateTime}
Return Value using $return
in function.json
Connect functions to Azure services
Environment variables default configuration provider
- Application Settings in azure function service
- local setting file
Identity-based connections are not supported with Durable Functions.
Authorization Levels
- Anonymous - No Api Key required.
- function - a function-specific API key is required (default)
- Admin - the master key is required
Durable Functions
a.k.a stateful functions
Application patterns
Function chaining:
a sequence of functions executes in a specific orde
the output of one function is applied to the input of another function
Fan-out/fan-in:
execute multiple functions in parallel and then wait for all functions to finish
Async HTTP APIs:
HTTP endpoint trigger the long-running action. Then, redirect the client to a status endpoint that the client polls to learn when the operation is finished
Function must include
DurableClient
input bindingMonitor:
recurring process in a workflow. An example is polling until specific conditions are met
Human interaction:
Involving humans in an automated process
timeouts and compensation logic
Durable Functions types and features
Orchestrator functions describe how actions are executed and the order in which actions are executed
- different types of actions, including activity functions, sub-orchestrations, waiting for external events, HTTP, and timers.
Activity Function: basic unit of work in a durable function.
DurableActivityContext
as a parameter Activity functions can only have a single value passed to them (Array / Tuple supported!). activity functions only guarantee at least once execution. You can trigger an activity function only from an orchestrator function.Entity functions: reading and updating state . Entities are accessed via a unique identifier Operations on entities require that you specify the
Entity ID
of the target entity, and theOperation name
,Client functions: The primary way to deliver these messages is by using an orchestrator client binding, or an entity client binding. Any non-orchestrator function can be a client function. What makes a function a client function is its use of the
durable client output binding
Orchestrator and entity functions cannot be triggered directly using the buttons in Azure Portal
Task hubs
logical container for durable storage resources
Task Hub in Azure Storage resources:
- 1 or more control queue
- 1 work-item queue
- 1 history table
- 1 instance table
- 1 storage container (1 or more lease BLOB)
Durable orchestrations
- define function workflows using procedural code
- call other durable functions synchronously and asynchronously
- Execution progress is automatically checkpointed
Features and patterns
- Sub-orchestrations
- Durable timers
- External events
- Error handling
- Critical sections (LockAsync)
- Calling HTTP endpoints
- Passing multiple parameters (Array / Tuple)
Durable Timers
implement delays or to set up timeouts with context.CreateTimer
Send and wait for events
wait and listen for external events.
handling human interaction or other external triggers
context.WaitForExternalEvent
RaiseEventAsync
method takes eventName
and eventData
as parameters. The event data must be JSON-serializable.