elixir and lambda talk with a telegram bot - paolo montrasio - codemotion milan 2016
If you can't read please download the document
TRANSCRIPT
Click to edit the title text format
Click to edit the outline text formatSecond Outline LevelThird Outline LevelFourth Outline LevelFifth Outline LevelSixth Outline LevelSeventh Outline Level
Elixir and Lambda talk with a Telegram botPaolo Montrasio
MILAN 25-26 NOVEMBER 2016
https://creativecommons.org/licenses/by-nc/3.0/
Freelancer
[email protected] github.com/pmontrasio
https://creativecommons.org/licenses/by-nc/3.0/
FreelancerSoftware architect
[email protected] github.com/pmontrasio
software design, APIs
team management
secure software development
FreelancerSoftware architectBackend developer
Rails Django Web2py Node
[email protected] github.com/pmontrasio
software design, APIs
team management
secure software development
FreelancerSoftware architectBackend developerMilano Chatbots
Rails Django Web2py Node
meetup.com/Milano-Chatbots-Meetup
[email protected] github.com/pmontrasio
software design, APIs
team management
secure software development
Telegram@PresenceAlertBot
It tells you how many WiFi mac address are in the air
Hellofor the menu/startto start/stopto end
webhook
receiver
When you talked to the bot Telegrams backend sent a HTTPS request to a webhook with JSON data. The webhook is a JavaScript function on AWS Lambda.
Users
webhook
It stores your user ID in a Dynamo DB table, Users.
Users
webhook
receiver
WiFi sensor
The Raspberry sends the count of unique WiFi mac addresses to another JavaScript function on AWS Lambda, once per minute.
Users
Presences
webhook
receiver
WiFi sensor
The count is timestamped and stored in another DynamoDB table, Presences.
Users
webhook
receiver
trigger
WiFi sensor
Presences
A trigger on Dynamo DB calls a third AWS Lambda function every time some data is added to Presences. That function gets all the Telegram user ids from Users and sends them a message with the count.
elixir
WiFi Sensor
The WiFi sensor on the Raspberry is implemented in Elixir.
elixir
Three layers
1. Functional
2. Object oriented
3. Process supervision
Elixir is a concurrent functional language running on the BEAM virtual machine, derived from Erlang with a Ruby like syntax.
Elixir processes exchange data by sending messages to each other, much like OO method calls. A typical Elixir application has many processes because they are cheap to create, run and send messages to. Millions of processes are not unheard of, much like millions of objects in OO languages.
But processes are concurrent and use all the cores of the machine.
Finally there is a process supervision layer to restart processes if the fail, much like upstart of systemd.
elixir
A look at the code
github.compmontrasio/wifi-sensor
elixir
elixir
The entry pointThe processesDependencies, mix deps.getCalling Erlang modulesPattern matchingHow to store state in a serverThe |> operator
The entry point is mix.exs, which by default runs the run function in lib/sensor.ex
Task.start_link creates a supervised process
ChannelHopper.hop: tail call optimization
MacAddressCounter: how to build a server
spawn fn - > creates a process. Think: new Class
:module.function is a call to an Erlang module
elixir
A more complex projectwith object orientation and process supervision
github.compmontrasio/decibel
Slides at
connettiva.eu/elixir-phoenix-raspberry-wifi (Italian)
Also check Elixir's object orientation at github.com/pmontrasio/elixir-oo
Receiver
github.compmontrasio/wifi-receiver
Everybody knows AWS Lambda?
Show the function at
https://github.com/pmontrasio/wifi-receiver/blob/master/handler.js
new AWS.DynamoDB.DocumentClient() outside the function, to save time (container reuse)
Easy but we must automate the deployment and the creation of the https endpoint.
serverless.ymlserverless deployInstall Dynamo DB locallyWhere to init the clientHow to test
$ serverless create --template aws-nodejs --name receiver
serverless.yml defines how to create the environment on AWS Lambda and how to deploy the application.
docs/Serverless_Setup.md is step by step guide at how to create and deploy the receiver.
docs/DynamoDB.md to install Dynamo DB locally
test/README.md on how to test. The important point is to be able to run the assertions in the callback run at the end of the function.
Webhook and Trigger
github.compmontrasio/wifi-presence-bot
Register the webhookReceive messagesConfigure the triggerSend messages
The webhook must be registered on Telegram.
presenceAlertWebhook gets the message in event.body.message
presenceNotifier can be called once with many database Records, in the event.Records array.
The trigger must be configured manually in the AWS console. See README.md for the details
Messages are sent with a POST to Telegrams.
Dont use npm modules unless you really have to: every ms is important. Billed by 100 ms units.
News
AWS Lambda environment variables and serverless architecture
serverless 1.1$ serverless invoke local -f FUNCTION
Alternatives
Google Cloud Functions, Azure functions
Apex, Gordon
https://aws.amazon.com/blogs/aws/new-for-aws-lambda-environment-variables-and-serverless-application-model/
https://cloud.google.com/functions/ https://azure.microsoft.com/en-us/services/functions/ http://apex.run/ https://github.com/jorgebastida/gordon