Azure Functions + F# talk at F# Exchange 2018

1. AzureF#unctions
@MikhailShilkov
https://mikhail.io

7. • Runs on top of App Service
• Web Jobs
• WebJobs SDK

8. • Consumption Plan
• Fixed Plan
• Self-hosted Runtime (preview)

9. • £0.15 per million executions
• £12 per million GB*s
• Free: 400,000 GB*s / 1 million executions

10. • Timer
• HTTP
• Queue / Service Bus / Event Hub
• Blob
• Cosmos DB Change
• Event Grid (and your custom events)
• Integrations (Logic Apps, Stream
Analytics, …)

11. Languages
• C#
• Javascript
• F#
• Java
• Others, experimental

14. // run.fsx
let run (myTimer: TimerInfo, log: TraceWriter) =
log.Info "Welcome to F# eXchange"

15. // function.json
{
"bindings": [
{
"type": "timerTrigger",
"name": "myTimer",
"schedule": "0 * * * * *"
}
]
}
Triggered on schedule
Cron expression

16. Log
Code
Files

20. Functions CLI

21. • Visual Studio Code + Ionide
• Paket
• FAKE
• Expecto
• Type Providers
• …

22. namespace PrecompiledApp
open Microsoft.AspNetCore.Mvc
open Microsoft.AspNetCore.Http
open Microsoft.Azure.WebJobs.Host
module PrecompiledHttp =
let run(req: HttpRequest, log: TraceWriter) =
log.Info "HTTP is easy with Azure Functions"
ContentResult(Content = "Precompiled F# FTW")

23. {
"bindings": [
{
"type": "httpTrigger",
"methods": ["get"],
"name": "req",
"route": "hellohttp"
}
],
"scriptFile": "../bin/PrecompiledApp.dll",
"entryPoint": "PrecompiledApp.PrecompiledHttp.run"
}
Triggered when this URL is requested
What to invoke

24. [<FunctionName("YourFunctionName")>]
let run(
[<HttpTrigger>] req: HttpRequest,
log: TraceWriter) =
log.Info "F# HTTP function smooshed your request."
ContentResult("function.json gets auto-generated")
It’s a Function…
… triggered by HTTP

25. {
"generatedBy": "Microsoft.NET.Sdk.Functions.Generator-1.0.9",
"configurationSource": "attributes",
"bindings": [
{
"type": "httpTrigger",
"name": "req"
}
],
"scriptFile": "../bin/AttributeBasedApp.dll",
"entryPoint": "AttributeBasedApp.AttributeBased.run"
}
Source of truth

26. [<FunctionName("Results")>]
let run([<HttpTrigger(AuthorizationLevel.Anonymous,
"get", "options", Route = "/products")>]
req,
[<DocumentDB("testdb", "testcollection",
ConnectionStringSetting = "CosmosDB",
SqlQuery = "SELECT top 2 * FROM c order by c._ts desc")>]
documents,
[<Table("SentimentTable", "DefaultPartition")>]
resultsTable) =
// ...

28. {
"bindings": [
{
"type": "queueTrigger",
"name": "tweet",
"queueName": "twitter"
}
]
}

29. {
"bindings": [
{
"type": "queueTrigger",
"name": "tweet",
"queueName": "twitter"
},
{
"direction": "out",
"name": "$return",
"type": "table",
"tableName": "Sentiment"
}
]
}
Return value goes to Table Storage

30. let run (tweet: Tweet): SentimentResult =
let score = TextAnalyticsAPI.SentimentScore(tweet.Text)
SentimentResult(
PartitionKey = "twitter",
RowKey = tweet.Id,
Text = tweet.Text,
Score = score)

32. {
"bindings": [
{
"type": "httpTrigger",
"name": "req",
"route": "{filename}/{name}"
},
{
"direction": "in",
"name": "template",
"type": "blob",
"path": "html/{filename}.html"
},
{
"type": "http",
"name": "$return",
"direction": "out"
}
]
}
Link

33. let run(req: HttpRequestMessage,
template: string,
name: string) =
let html = template.Replace("%name%", name)
ContentResult(
Content = html,
ContentType = "text/html")
Comes from Blob storage

34. Function
Chaining Functions

36. Workflow Orchestration

37. [<FunctionName("ChargeCreditCard")>]
let ChargeCreditCard([<ActivityTrigger>] order) = //...
[<FunctionName("ReserveStock")>]
let ReserveStock([<ActivityTrigger>] order) = //...
[<FunctionName("PlanShipment")>]
let PlanShipment([<ActivityTrigger>] order) = //...

38. open FSharp.Control.Tasks
[<FunctionName("OrderOrchestrator")>]
let run([<OrchestrationTrigger>] context: DurableOrchestrationContext) = task {
let order = context.GetInput<Order>()
let! payment = context.CallActivityAsync<Payment>("ChargeCreditCard", order)
let! stockItem = context.CallActivityAsync<StockItem>("ReserveStock", order)
let! shipment = context.CallActivityAsync<Shipment>("PlanShipment", order)
return OrderConfirmation(order, payment, stockItem, shipment)
}
async won’t work

42. • Stateless mindset
• But instances are reused between executions

43. 0
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minutes

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45. 0
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Requests 50th 90th 95th

47. • .NET Framework 4.7.1
• GA
• All triggers supported
• Full scalability
• .NET Core 2.0
• Preview
• WIP
• Limited scalability

48. • Fast growth => Technical debt
• No uniformity among Binding types
• Reference version conflicts

49. • External paket.lock defined by Azure Functions team
• Use it in paket.dependencies:

50. • “Developed in the open”
• Scale Controller is not open

51. • “Glue”: webhooks, integration with Azure services
• Prototypes
• Low traffic apps
• Unusual load profiles
• Message/event processing

52. • Small, green-field, event-driven application
• Avoid migration of existing complex projects (yet)

53. Thank You!