May 17, 2019

Guide on Developing Azure Functions locally

Why

I have spend way too much time on figuring out how to create local development environment for working on Azure Functions. Most of the time was spent on reading Microsoft's documentation on this topic. Hopefully this guide will save you some time :)

The guide had been prepared on Ubuntu and verified as well. Additionaly my coworker verified it to work on macOS High Sierra. If you are here to create your first Azure Function locally please read along.

What are azure functions

Azure Functions are small pieces of code that are run on Azure infrastructure in a serverless fashion. The Infrastructure, provisioning, scaling is Azure's responsibility. If you wish to read more below are links to detailed explanation by Azure team. I'd recommend at least skimming the first one.

Software required for local development

There are a couple of tools required to be able to develop locally.

  • npm, tooling is mostly in JS/TS
  • .NET Core SDK, required for function extensions
  • Azure Functions Core Tools (later referred as AFCT)
  • Azurite legacy, for storage emulation. It works with Blob, Table, and Queue storages. Legacy is required as the current one supports only Blob storage.
  • Docker

Handling http requests

This part explains how to create a function that is triggered by HTTP request and responds with HTTP response.

Create Azure Function project

Start with calling func init HTTPFunc in the directory of your choosing. You will be asked a couple of questions regarding your project.

majki@enchilada ~/projects/azure-tracker-local
% func init HTTPFunction
Select a worker runtime:
  1. dotnet
    1. node
    2. python (preview)
    3. powershell (preview) Choose option: 2 node Select a Language:
    4. javascript
    5. typescript Choose option: 2 typescript Writing .funcignore Writing package.json Writing tsconfig.json Writing .gitignore Writing host.json Writing local.settings.json Writing /home/majki/projects/azure-tracker-local/HTTPFunction/.vscode/extensions.json
### Create Azure Function

Create function next. As in the previous step you will be asked questions regarding the function you wish to create. I selected 8. HTTP Trigger as this function should respond to HTTP requests.

majki@enchilada ~/projects/azure-tracker-local
% cd HTTPFunction
majki@enchilada ~/projects/azure-tracker-local/HTTPFunction
% func new
Select a template:
  1. Azure Blob Storage trigger
    1. Azure Cosmos DB trigger
    2. Durable Functions activity
    3. Durable Functions HTTP starter
    4. Durable Functions orchestrator
    5. Azure Event Grid trigger
    6. Azure Event Hub trigger
    7. HTTP trigger
    8. IoT Hub (Event Hub)
    9. Azure Queue Storage trigger
    10. SendGrid
    11. Azure Service Bus Queue trigger
    12. Azure Service Bus Topic trigger
    13. Timer trigger Choose option: 8 HTTP trigger Function name: [HttpTrigger] Writing /home/majki/projects/azure-tracker-local/HTTPFunction/HttpTrigger/index.ts Writing /home/majki/projects/azure-tracker-local/HTTPFunction/HttpTrigger/function.json The function "HttpTrigger" was created successfully from the "HTTP trigger" template.
### Install dependencies
npm install

Run function

npm run start

Verify

majki@enchilada ~
% curl http://localhost:7071/api/HttpTrigger
Please pass a name on the query string or in the request body%
majki@enchilada ~
% curl "http://localhost:7071/api/HttpTrigger\?name\=Mike"
Hello Mike

Handling Queue Storage

This part explains how to create a function that is triggered by HTTP request to send a message onto Queue Storage.

Install storage emulation

On windows, you may go with emulator provided by Microsoft. On Ubuntu, there is community sourced Azurite. Unfortunately, the most recent version does not support Queue Storage. For queues, install version 2.7.0 by following instructions.

Create Azure Function project

Start with calling func init HTTPFunc in directory of your choosing. You will be asked couple questions regarding your project.

majki@enchilada ~/projects/azure-tracker-local
% func init HTTPFunction
Select a worker runtime:
  1. dotnet
    1. node
    2. python (preview)
    3. powershell (preview) Choose option: 2 node Select a Language:
    4. javascript
    5. typescript Choose option: 2 typescript Writing .funcignore Writing package.json Writing tsconfig.json Writing .gitignore Writing host.json Writing local.settings.json Writing /home/majki/projects/azure-tracker-local/HTTPFunction/.vscode/extensions.json
### Create function

Create function next. As in previous step you will be asked questions regarding function you wish to create. I selected 8. HTTP Trigger as this function should respond to HTTP requests, it will in response send message to Queue Storage.

majki@enchilada ~/projects/azure-tracker-local
% cd HTTPFunction
majki@enchilada ~/projects/azure-tracker-local/HTTPFunction
% func new
Select a template:
  1. Azure Blob Storage trigger
    1. Azure Cosmos DB trigger
    2. Durable Functions activity
    3. Durable Functions HTTP starter
    4. Durable Functions orchestrator
    5. Azure Event Grid trigger
    6. Azure Event Hub trigger
    7. HTTP trigger
    8. IoT Hub (Event Hub)
    9. Azure Queue Storage trigger
    10. SendGrid
    11. Azure Service Bus Queue trigger
    12. Azure Service Bus Topic trigger
    13. Timer trigger Choose option: 8 HTTP trigger Function name: [HttpTrigger] HTTP2Queue Writing /home/majki/projects/azure-tracker-local/HTTPFunction/HTTP2Queue/index.ts Writing /home/majki/projects/azure-tracker-local/HTTPFunction/HTTP2Queue/function.json The function "HTTP2Queue" was created successfully from the "HTTP trigger" template.
### Configure function output

In the editor open function.json file located in the directory named after the name of the function. Remove the section related to http output and replace with the queue output as shown below:

{
  "type": "queue",
  "direction": "out",
  "name": "msg",
  "queueName": "outgoingqueue",
  "connection": "MyQueueConnectionString"
}

The file is suppose to look like this:

{
    "bindings": [
        {
            "authLevel": "function",
            "type": "httpTrigger",
            "direction": "in",
            "name": "req",
            "methods": [
                "get",
                "post"
            ]
        },
        {
            "type": "queue",
            "direction": "out",
            "name": "msg",
            "queueName": "outgoingqueue",
            "connection": "MyQueueConnectionString"
        }
    ],
    "scriptFile": "../dist/HTTP2Queue/index.js"
}

Configure queue connection

Some connections defined in function.json require to have a connection string. After adding an outgoing queue connection you need to add a connection string as well. String has to be added to Define connection in local.settings.json by adding "MyQeueueConnectionString". The value of this string is taken from documentation of Azurite.

{
    "IsEncrypted": false,
    "Values": {
        "FUNCTIONS_WORKER_RUNTIME": "node",
        "AzureWebJobsStorage": "{AzureWebJobsStorage}",
        "MyQueueConnectionString": "DefaultEndpointsProtocol=http;AccountName=devstoreaccount1;AccountKey=Eby8vdM02xNOcqFlqUwJPLlmEtlCDXJ1OUzFT50uSRZ6IFsuFq2UVErCz4I6tq/K1SZFPTOtr/KBHBeksoGMGw==;QueueEndpoint=http://127.0.0.1:10001/devstoreaccount1;"
    }
}

Install dependencies

npm install

Install extensions

Since we are using an output that is different than http, we have to install storage extensions to make the queue work.

func extensions install

Run azurite

Run Azurite by using Docker

docker run -e executable=queue -d -t -p 10001:10001 -v queue_Storage:/opt/azurite/folder arafato/azurite

More information on how to run it is here.

Run function

In order to put any message on the queue, the function needs to be modified a bit. Please change it accordingly.

const httpTrigger: AzureFunction = async function (context: Context, req: HttpRequest): Promise<void> {
    context.log('HTTP trigger function processed a request.');
    const name = (req.query.name || (req.body && req.body.name));
    context.bindings.msg = name;
    context.done();
};

And then

npm run start

Verify

Now we can see how this is working. We are going to call our function a couple of times and then see what messages had been put on the queue.

majki@enchilada ~
% curl "http://127.0.0.1:7071/api/HTTP2Queue?name=Mike"
HTTP/1.1 204 No Content
Content-Length: 0
Date: Tue, 14 May 2019 06:39:25 GMT
Server: Kestrel
majki@enchilada ~
% curl "http://127.0.0.1:7071/api/HTTP2Queue?name=Mickey"
HTTP/1.1 204 No Content
Content-Length: 0
Date: Tue, 14 May 2019 06:39:28 GMT
Server: Kestrel

There should be two messages on the queue at this moment. We can query the queue by running:

majki@enchilada ~
% curl "http://127.0.0.1:10001/devstoreaccount1/outgoingqueue/messages?peekonly=true&numofmessages=10"
HTTP/1.1 200 OK
Connection: keep-alive
Content-Length: 885
Content-Type: application/xml; charset=utf-8
ETag: W/"375-pdRmS0dxI0dhZlfRbwGMunhL+WM"
X-Powered-By: Express
date: Tue, 14 May 2019 06:42:39 GMT
x-ms-request-id: 77856d80-7613-11e9-afc4-b5f560b4039e
x-ms-version: 2016-05-31
<?xml version='1.0'?><QueueMessagesList><QueueMessage><MessageId>cae264ef-74bd-4bde-b03e-01be8821968a</MessageId><InsertionTime>Tue, 14 May 2019 06:29:04 GMT</InsertionTime><ExpirationTime>Tue, 21 May 2019 06:29:04 GMT</ExpirationTime><DequeueCount>0</DequeueCount><MessageText>TWlrZQ==</MessageText></QueueMessage><QueueMessage><MessageId>13732448-a498-4fc5-85cf-8c4afafe082b</MessageId><InsertionTime>Tue, 14 May 2019 06:39:25 GMT</InsertionTime><ExpirationTime>Tue, 21 May 2019 06:39:25 GMT</ExpirationTime><DequeueCount>0</DequeueCount><MessageText>TWlrZQ==</MessageText></QueueMessage></QueueMessagesList>

Azurite supports Queue Storage API, so if you need to know more operations read linked docs.

Tags: azure typescript azure functions