Add your own blockchain scraper

In order to add your own scraper for a blockchain supply source, you must adhere to our format. We use Go modules for our scrapers, so that each data provider is living as an independent module.

Directory structure

The working directory for blockchain scrapers is diadata/internal/pkg/blockchain-scrapers/blockchains. Each scrapper should comply with the following folder structure currencyName/scrappers/currencySymbol/currencySymbol.go for example for bitcoin will look like bitcoin/scrapers/btc/btc.go. You must provide a Dockerfile for your blockchain client and for the Go wrapper that connects to our database. An example dockerfile is provided for the Go bindings with a bitcoind client scraping the Bitcoin blockchain. The file should be named build/Dockerfile-symbol for this example build/Dockerfile-btc

FROM golang:1.14 as build
​
WORKDIR $GOPATH
​
COPY . .
​
WORKDIR $GOPATH/src/github.com/diadata-org/diadata/internal/pkg/blockchain-scrapers/blockchains/bitcoin/scrapers/btc
​
RUN go install
​
FROM gcr.io/distroless/base
​
COPY --from=build /go/bin/btc /bin/btc
​
CMD ["btc"]

After cloning a container capable of executing Go, the files from the working directory are copied into the container. Next, the go program located in diadata/internal/pkg/blockchain-scrapers/blockchains/bitcoin/scrapers/btc is built and installed and the finished binary is placed into a mininal distroless container. From there it is executed using the statement in the last line.

Blockchain Client

The bitcoind itself is initialized directly from the file docker-compose.bitcoin.yml. Ideally, all blockchain clients are run from there directly

version: '3.2'
​
services:
  bitcoin:
    image:
      kylemanna/bitcoind
    user: "1000"
    volumes:
      - /home/srv/bitcoin:/bitcoin
    command: btc_oneshot -printtoconsole -prune=550 -rpcallowip=::/0 -disablewallet -rpcpassword=mysecretrpcdiapassword -rpcuser=mysecretrpcdiauser
    logging:
      options:
        max-size: "50m"
    networks:
      - scrapers-network
    deploy:
      mode: global
      restart_policy:
        delay: 2s
        window: 20s

Make sure to enable pruning so that only the latest mined blocks are stored in the container. Add persistency in /home/srv for the daemon data, so it can restart without needing to resynch the blockchain.

Go Wrapper

For your Go code, also add an entry into the docker-compose file so that your Dockerfile is automatically called. An example entry should look something like this

  btc:
    build:
      context: ../../../..
    build:
      context: $GOPATH
      dockerfile: $GOPATH/src/github.com/diadata-org/diadata/build/Dockerfile-btc
    image: ${DOCKER_HUB_LOGIN}/${STACKNAME}_btc:latest
    networks:
      - scrapers-network
    logging:
      options:
        max-size: "50m"
    secrets:
      - api_diadata

Be sure to add your container to the scrapers-network virtual network. Your credentials for the DIA API should be handled by the secrets directive in the section of your blockchain client. To initialize the API from Go you can create

var api *dia.Client

and then call

var c dia.ConfigApi
configFile := "/run/secrets/api_diadata"
err := gonfig.GetConf(configFile, &c)
if err != nil {
  configFile = "../config/secrets/api_diadata.json"
  err = gonfig.GetConf(configFile, &c)
}
if err != nil {
  log.Println(err)
} else {
  log.Println("Loaded secret in", configFile)
}
api = dia.NewClient(&c)

For sending supply data to DIA, you can use SendSupply in the ApiClient.go file.

This is the basic structure of these files. Run your Docker instance by calling

docker run <your instance>

from the main directory. With docker-compose up you can test the entire system with your cryptocurrency VM and your Go wrapper in a virtual network.