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Rapid prototyping using Azure Functions - A Walk on the Wild Side

Samrat Saha08.29.2016

SMS Based Survey SystemUsers can text responses to a questionUsers can opt in/out along with preferencesTopics that are time basedAutomatic detection of topicStart with a POC

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Traditional ApproachWay too many ways to skin this cat - prime concern is infrastructure

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Cloud Approach● On-Demand● Horizontal Scaling● Paradigms (Paxos, Consistent Hashing, Redundancies,

SLA’S!)● Azure

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Azure Functions● Event driven on demand compute resources● Serverless Architecture● WebJobs SDK as a Service● A function runs in the context of a Function App

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Bindings● Triggers: HTTP, Events, Queues● Input: Blob Storage, Table Storage, DocumentDB● Output

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Function App Folder Structure● WWWRoot

○ host.json○ function1

• run.csx• function.json• bin

○ function 2• run.csx• function.json• Bin

○ sharedAssemblies• usefulAssembly.dll

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host.json● Runtime specific config: Impacts entire function app● Can set function timeouts, overall behaviors like service bus

settings{

"functionTimeout": "00:10:00"

}

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function.json{ "bindings": [ { "name": "queueItem", "type": "serviceBusTrigger", "direction": "in", "queueName": "lc_incoming_sms_queue", "connection": "lc_incoming_sms_read_connection", "accessRights": "Listen" }, { "type": "serviceBus", "name": "outputSbMsg", "queueName": "lc_bluemix_results_queue", "connection": "lc_bluemix_results_manage_connection", "accessRights": "Manage", "direction": "out" } ], "disabled": false}

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run.csx#r "../sharedAssemblies/LC-SMS-Quote-DomainModel.dll"using System;using System.Threading.Tasks;using LC_SMS_DomainModel;using LC_SMS_DomainModel.AzureLogging;private static TraceWriter _logger;public static void Run(string queueItem, out string outputSbMsg, TraceWriter log){ _logger = log; log.Info($"C# ServiceBus queue trigger function processed message: {queueItem}"); AzureLogger.InfoCallback = new AzureLogger.InfoDelegate(InfoDelegate); LCSMSDomainModel domainModel = new LCSMSDomainModel(); domainModel.Init(); String response = domainModel.HandleIncomingSMS(queueItem); outputSbMsg = response;}public static void VerboseDelegate(String message, String source){ _logger.Verbose(message);}public static void InfoDelegate(String message, String source=null){ _logger.Info(message);}

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Leveraging External Assemblies● Some namespaces like System automatically imported● Framework assemblies (automatically available through

Azure Functions Hosting Environment)#r “System.Web.Http"

● bin folder relative to function#r “functionSpecificUsefuldll.dll"

● Shared assemblies in under webroot, accessible by relative path

#r "../sharedAssemblies/LC-SMS-Quote-DomainModel.dll"● Inside assembly to access config:

String storageAccountId = Environment.GetEnvironmentVariable(CONFIG_STORAGE_ACCOUNT,EnvironmentVariableTarget.Process);

● Use Project.Json for NuGet

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Scaling● App Service Plan: Dedicated VM, leverage under utilized

resources, good for long running● Dynamic Service Plan: Function app instance...more

instances can be added dynamically. Best use for intermittent/ short running

● Parallel Execution: Single threaded function runtime-> Scale to multiple

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Function Chaining● Call a function from another● Message Queue allows for decoupling● Allows for semi-pure functional programming

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Where does this leave us?● Prototype being worked on (for this example)● People loved it...got sold to a client

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ThanksCentareLC

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