Explore Azure Functions

Question 1

What are azure functions?

Answer 1

• serverless solution that allow you to write less code, maintain less infrastructure and save on costs
• No worries about managing infrastructure, azure provides all the up-to-date resources needed to keep apps running

Question 2

What are the two kep components of azure functions?

Answer 2

• Triggers; provide a way to start execution of code
• Bindings; simplify coding for input and output data
• All functions must have one trigger but they do not have to have a binding

Question 3

How are functions and logic apps different from one another? (Long answer)

Answer 3

• Functions are serverless compute service, logic apps are serverless workflow integration platform
• Functions use code to create orchestrations, logic apps use GUI/Config files
• Functions are code first (imperative), logic apps are designer-first (declarative)
• Each activity is an azure function that we write code for, logic apps has a collection of ready-made actions instead
• Functions use app insights, logic apps use monitor logs

Question 4

What are orchestrations in terms of functions

Answer 4

• a collection of functions that are executed to complete a task

Question 5

How are functions and webjobs similar?

Answer 5

• Both code first integration services designed for devs
• built on app service and support features such as source control integration, authentication and monitoring with app insights
• functions are built on top of webjobs SDK, sharing many of the same triggers and connections

Question 6

How are functions and webjobs different?

Answer 6

• Only functions provide automatic scaling, development and testing browser, pay-per-use pricing and integration with logic apps
• Webjob triggers include Timer, queues, blobs, service bus queues and topics, cosmos DB, event hubs and file system
• Function triggers include all of those plus HTTP/WebHook and azure event grid
• functions offer more dev productivity and offer more options for programming languages, dev environments, azure service integration and pricing

Question 7

What hosting plans are availble for functions?

Answer 7

• consumption
• premium
• app service/dedicated
• all available on windows and linux

Question 8

What does the function hosting plan dictate?

Answer 8

• how your function app is scaled
• the resources available to each function app instance
• support for advanced functionality such as vnet connectivity

Question 9

What are the benefits of the consumption function hosting plan?

Answer 9

• default hosting plan that scales automatically and you only pay for compute resources when your functions are running
• Instances of the functions host are dynamically added and removed based on the number of incoming events
• Timeout default duration is 5 mins with max of 10

Question 10

What are the benefits of the premium function hosting plan?

Answer 10

• auto scales based on demand using pre-warmed workers which run apps with no delay after being idle
• runs on more powerful instances and connections to vnets
• timeout default duration is 30 mins with unlimited max

Question 11

What are the benefits of the dedicated function hosting plan?

Answer 11

• run your functions with an app service plan at regular app service plan rates
• best for long-running scenarios where durable functions cant be used
• timeout default duration is 30 mins with unlimited max

Question 12

What are the two other hosting options for functions?

Answer 12

• App Service Environment (ASE); app service feature that provides a fully isolated and dedicated env for securely running app service apps at high scale
• Kubernetes; provides a fully isolated and dedicated env running on top of the kubernetes platform
• both provide the highest level of control and isolation in which to run your functions apps

Question 13

How does scaling work on the consumption function hosting plan?

Answer 13

• event driven, scale out automatically even during periods of high load
• adds more instances of the functions host based on the number of incoming trigger events
• max instances are 200 on windows and 100 on linux per function app

Question 14

How does scaling work on the premium function hosting plan?

Answer 14

• event driven and identitcal to function app
• max instances are 100 on windows and 20-100 on linux

Question 14

How does scaling work on the dedicated function hosting plan?

Answer 14

• manual/autoscale
• 10-20 max instances

Question 15

How does scaling work on the ASE and Kubernetes hosting plans?

Answer 15

• ASE; manual/autoscale with 100 max instances
• Kubernetes; event driven autoscale for Kubernetes clusters using KEDA with instances varying by cluster

Question 16

Why does a function app require a storage account?

Answer 16

• requires a general storage account which supports blob, queue, file and table storage
• functions rely on azure storage for operations such as managing triggers and logging function executions
• the same storage account used by your function can also be used by your triggers and binding to store your app data
• …however for storage intensive-operatiosn you should use a separate storage account

Question 17

How do consumption and premium function hosting plans handle scaling?

Answer 17

• add more instances of function host
• in consumption each instance is limited to 1.5GB of memory and 1 CPU
• an instance is the entire function app, meaning all functions in the app share resource within an instance and scale out together
• function apps that share the same plan scale independently
• In premium plan the plan size determines the available memory and CPU for all apps in that plan on that instance

Question 18

Where are function code files stored?

Answer 18

• Azure file shares on the functions main storage account
• when you delete the main storage account of the function app, the function doe files are deleted and cant be recovered

Question 19

What is the scale controller?

Answer 19

• Functions use scale controller to monitor the rate of eventsand determine whether to scale out or in
• uses heuristics for each trigger type
• e.g. when using a queue storage trigger, it scales based on queue length and age of oldest queue message
• unit of scaling for functions is the function app
• when scaled out more resources are allocated to run multiple instance of functions host

Question 20

What happens if the function app is idle for several mins?

Answer 20

• Platform may scale the number of instances on which your app runs in to zero
• the next request has the added latency of scaling from zero to one]
• this latency is known as a cold start

Question 21

What are the intricacies of scaling in Azure functions?

Answer 21

Max instances
- A single function app only scales out to a max of 200 instances
- a single interface may process more than one msg or request at a time though so there isn’t a set limit on number of concurrent executions
New instance rate
- for HTTP triggers new instances are allocated at most once per second
- for non HTTP triggers new instances are allocated at most every 30 seconds

Question 22

How can we specify a lower max instance value for a function app?

Answer 22

• By modifying the ‘functionappscalelimit’ value
• can be set to 0 or null for unrestricted or a value between 1 and the app max