A simple service that will send me a text message when bitcoin price above/below certain price.

Some Thoughts

I have this need to track bitcoin price for my friend, so I could buy coins for him once the price is below certain price.

Most coin price monitoring websites offer email notification for free, not for SMS. So I thought I could build a 'free' SMS notification service.

I want this to be done quickly, so give serverless a go, I used aws console to spin up the services,turned out it's really quick to build APIs once the infrastructure is ready.

Then I'd like to preserve what I've done, best way is in code, by default, we use terraform, but I want to try aws cli, and now I know why by default use terraform...

There are many ways to spin up AWS infrastructure:

• terraform
• cloud formation
• cli
• aws console

Through console is quick to try out things, but not maintainable

CLI is handy for ops work, has early access to new features, but complicate for infrastructure provisioning

Terraform is good for infrastructure as code, but feature updates can be slow.

Prerequisite

• An AWS account
• An IAM admin role in place (AWS common sense)

The steps below can be covert to a shell script, can extract output as next command's input via tools like jq

Setup a SNS topic and its subscribers

aws sns create-topic --name my-topic --profile ${profile-name}

aws sns subscribe --topic-arn ${topic-arn} --protocol ${protocol} --notification-endpoint ${endpoint} --profile ${p}

eg. protocol: sms, endpoint: +4412345678

Create lambda execution role

Create a role for lambda execution

aws iam create-role --profile ${p} --role-name ${my-lambda-exec-role} --assume-role-policy-document file://assume-role-policy.json

Attach 2 policies to the role

• arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole
• arn:aws:iam::aws:policy/AmazonSNSFullAccess

aws iam attach-role-policy --profile ${p} --role-name ${my-lambda-exec-role} --policy-arn arn:aws:iam::aws:policy/{ROLE}

Build lambda function

Build the go file

GOOS=linux go build bitcoin-alerting-func.go

Zip it
zip func.zip bitcoin-alerting-func

Create a lambda function to publish message to a SNS topic, which in turn will send messages to its subscribers, and return 200 (a requirement from cryptocurreyalerting.com webhook)

aws --profile ${p} lambda create-function --function-name ${my-lambda-func} --zip-file fileb://func.zip --handler ${my-lambda-func} --runtime go1.x --role ${lambda-exec-role-arn}

lambda-exec-role-arn format: arn:aws:iam::${iam-user-id}:role/${role-name}

Create API via apigatewayv2

apigatewayv2 creates HTTP API, POST endpoint, have the url to be added to cryptocurrencyalerting.com's webhook config, this API integrates with lambda function

It seems that the integration is not working via cli, so the walk around is to create a default endpoint, then create route, then attach integration via console

Create API (quick create): aws apigatewayv2 create-api --name my-rest-api --protocol-type HTTP --target ${my-lambda-func-arn} --profile ${p}

Create route:
aws apigatewayv2 create-route --profile ${p} --api-id ${api-id} --route-key "POST /alerts"

Config webhook

Config a webhook in cryptocurrencyalerting.com, specify desired condition to trigger the webhook