Chainlink External Adapters (TypeScript)

This repository contains the source code for Chainlink external adapters.

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Table of Contents

1. Getting Started
   • Requirements
   • Install Dependencies
   • Setup
   • Folder Structure
2. List of External Adapters
3. Running
   • Configuration
   • HTTP server
   • Docker
   • Single-Command Script
4. Advanced Features
   • Performance
     • Caching
     • Rate Limiting
     • Cache Warming
   • Multiple API Key Support
   • Bridge URL Query String Parameters
   • Ticker Overrides
5. Deployment
   • Container Images
   • Running from ECR
6. Contributing
   • Create a new adapter
   • HTTP server
   • Input
   • Output
   • Common Patterns
   • Testing

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Getting Started

Requirements

• Yarn

Install

yarn

Installs the dependencies for all workspaces.

Setup

yarn setup

Runs the setup step for all adapters. Typically this step just compiles TypeScript, but may involve other tasks.

Folder Structure

╠═.github - scripts automatically ran by the CI/CD workflow
║
╠═.husky - git hooks
║
╠═.vscode - code editor specific configuration
║
╠═.yarn - yarn 2 dependencies
║
╚═packages
    ║
    ╠══ composites - adapters composed of multiple other adapters for complex functionality
    ║
    ╠══ core - the internal framework used across all external adapters
    ║
    ╠══ examples - example templates for new external adapters
    ║
    ╠══ scripts - additional Node.js scripts for mono-repository management
    ║
    ╠══ sources - adapters that read data from a data provider's API.
    ║
    ╚══ targets - adapters that write data to a location, often a blockchain.

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External Adapters List

• Source

• Target

• Composite

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Running

External adapters should be run as long-lived processes. Each adapter may have configuration that is required to be supplied through environment variables.

Configuration

There may be required environment variables that must be provided to run an External Adapter. Please see the respective adapter's README for more specific information on the External Adapter that you would like to run.

Every External Adapter has some optional environment variables for customizing behavior and turning on advanced features. More documentation for these can be seen here

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There are two ways to run an External Adapter locally:

HTTP server

Use the start command while in the directory of the adapter that you would like to run:
(example for coingecko shown)

cd packages/sources/coingecko
yarn start

Docker

1. All of the external-adapters have a service that is created when the repo's docker-compose file is generated.

This can be done by running the following command in the root of the repository:

yarn generate:docker-compose

2. Next create a container image. Use the generated docker-compose.generated.yaml file along with docker-compose build.

docker-compose -f docker-compose.generated.yaml build [adapter-name]

Where [adapter-name] is replaced with the following:

Parameter	Description	Options
adapter-name	name of the external adapter package, usually the folder name with -adapeter as a suffix	See docker-compose.generated.yaml for list of services that can be used as options

For example the bravenewcoin external adapter uses bravenewcoin-adapter:

docker-compose -f docker-compose.generated.yaml build bravenewcoin-adapter

3. Then run it with:

docker-compose -f docker-compose.generated.yaml run -p 8080:8080 -e API_KEY='YOUR_API_KEY' bravenewcoin-adapter

Environment files can also be passed through a file:

docker run -p 8080:8080 --env-file="~/PATH_TO_ENV" -it proof-of-reserves-adapter:latest

(Docker environment file's string values do not use " or ' quote marks)

Single-Command Script

This command will start all of your external adapters with performance features enabled and with pre-defined metrics charts for each EA on a single server.

The first step will be to load up all of the environment variables that are needed across all of the External Adapters that will be ran. These can either be already be loaded into the environment or supplied to the startup script as a text file.

Starting from the root of the repository:

1. Ensure that the project is setup and that the docker-compose file has been generated

   yarn && yarn setup && yarn generate:docker-compose

2. Use the startup script by supplying every External Adapter that you would like to run and monitor.

The adapter will have the format of [[ADAPTER NAME]]-adapter.

For example:

cd grafana && ./scripts/compose.sh coingecko-adapter coinmarketcap-adapter

3. The running services can be found at the following ports:

• External Adapters - search docker-compose.generated.yaml for the name of your EA. The port it is running on will be found as the first number before the colon under ports.

coincodex-adapter:
    image: coincodex-adapter:0.0.4
    ports:
      - 8112:8080 <----------- The first number before the colon here
    build:
      context: ..
      dockerfile: ./Dockerfile
      args:
        location: packages/sources/coincodex
        package: "@chainlink/coincodex-adapter"
      labels:
        com.chainlinklabs.external-adapter-type: sources
    environment:
      - EA_PORT=${EA_PORT}

• Prometheus - http://localhost:9090/graph

• Grafana - http://localhost:3000/

  The default login is:

  • Username: admin
  • Password: admin

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Advanced Features

Performance

The following section details mechanisms that reduce the number of API calls made from external adapters. It is highly recommended to turn on the following three middlewares.

Caching

Caching allows for the EA to store successful responses and facilitate faster future response times.

To enable, the following environment variables must be set:

export CACHE_ENABLED=true

See /bootstrap for more details and configuration options.

Rate Limiting

The Rate Limit middleware prevents hitting rate limit issues with data providers. This is done by adjusting how long a request lives in the cache based on the available capacity of your API subscription plan. To enable use the following environment keys:

export EXPERIMENTAL_RATE_LIMIT_ENABLED=true CACHE_ENABLED=true

There are two options for defining API subscription capacity:

1. Manual setting (example shown for limit at 10 requests/minute)

export RATE_LIMIT_CAPACITY=60

2. Limits by provider data (example for Coingecko free tier)

export RATE_LIMIT_API_PROVIDER=coingecko RATE_LIMIT_API_TIER=free

Preset tiers/plans can be found here and use the corresponding provider and tierName.

See /bootstrap for more details and configuration options.

Cache Warming

When a new unique request comes in to an EA the Cache Warming middleware will begin polling the API on an interval ensure that data is always ready to be served and is as fresh as possible.

To enable, the following environment variables must be set:

export CACHE_ENABLED=true EXPERIMENTAL_WARMUP_ENABLED=true

The cache will begin polling once the first request has been received.

See /bootstrap for more details and configuration options.

Multiple API Key Support

In order to use multiple API keys for an adapter, simply comma delimit the keys where you define the environment variable. This will work for an arbitrary number of keys.

API_KEY=myapikey1,myapikey2,myapikey3

The external adapter will then randomly rotate the keys. Over time this should balance out the number of requests between each of the API keys.

Bridge URL Query String Parameters

Additional input parameters can be passed to an External Adapter through the Bridge URL that is specified when connecting an External Adapter to the core node.

This is useful in scenarios where when running multiple External Adapters to service a job spec there is a single External Adapter's behavior needs to be customized without affecting the others.

Ticker Overrides

There are cases where a certain data provider might have different ticker symbol to represent a cryptocurrency, often when there are multiple cryptocurrencies that share the same ticker.

To help query the correct symbols the External Adapter request can contain an object of symbol overrides named overrides:

"overrides": {
      "coinmarketcap": {
        "RAI": "RAI2"
      }
    },

In the above example when the coinmarketcap External Adapter is requested with a base of RAI the ticker will be changed to RAI2.

---

Deployment

Container Images

Images are being published to Chainlink's public AWS ECR repositories: public.ecr.aws/chainlink/adapters

They can also be found in the public gallery, the registry name is chainlink. (e.g. https://gallery.ecr.aws/chainlink/adapters/1forge-adapter)

The External Adapters are being tagged with semantic releases to allow for automated upgrades.

Running from ECR

The EA container image can be download by using the docker pull command. For example:

docker pull public.ecr.aws/chainlink/adapters/1forge-adapter:latest

To run the image use the docker run command. For example:

docker run -p 8080:8080 -e API_KEY='YOUR_API_KEY' public.ecr.aws/chainlink/adapters/1forge-adapter:latest

It can be helpful to pass a text file to the container to handle giving multiple environment variables:

docker run -p 8080:8080 --env-file=[[path to your env file]] public.ecr.aws/chainlink/adapters/1forge-adapter:latest

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Contributing

Create a new adapter

To get started from one of the example adapters seen in examples use the new script with two arguments:

yarn new [template-type] [name-of-adapter]

Parameter	Description	Options
template-type	the name of the template to use	composites, sources
name-of-adapter	what to call the new adapter	user-defined

For example

yarn new source my-new-adapter

If on a Mac, this requires gnu-sed to be installed and set as the default for the command sed.

Input

When flux monitor or OCR jobs from the core Chainlink node post to external adapters, the request body looks as follows:

{
  "id": "2cae6a10e5184aa685c3428964b02418",
  "data": { "from": "ETH", "to": "USD" },
  "meta": {
    "latestAnswer": 39307000000,
    "updatedAt": 1616448197
  }
}

The updatedAt field is a unix timestamp representing when the latestAnswer was computed.

Optionally data parameters can also be passed via a query string added to the Bridge URL like: {ENDPOINT}?from=ETH&to=USD. This is useful when trying to conform to unified input parameters.

Output

The External Adapter will do some processing, often request data from an API, and return the following response structure:

  {
    "jobRunID": "2cae6a10e5184aa685c3428964b02418",
    "statusCode": 200,
    "data": {
      "result": 3000 // Result for Flux Monitor jobs.
      // ... Response data
    },
    "result": 3000 // Result for OCR jobs.
    "maxAge": 222, // [OPTIONAL] metadata for how long the request is cached for
    "debug": { // [OPTIONAL]
      // Additional metadata from the EA framework used for tracking metrics
    }
  }

Common Patterns

• For handling big numbers the BigNumber.js dependency should be used for integer operations, and Decimal for floating point operations. By default decimal.js uses a precision of 20. As we could lose some precision with really large numbers, it should be updated to a higher precision before usage:

Decimal.set({ precision: 100 })

Common Issues

Testing

In order to test adapters locally, you may need to set an $API_KEY environment variable for the given API or other required environment variables.

Make sure you run these commands from the ROOT of this monorepo.

# Build all packages
yarn setup

# Run all unit tests
yarn test:unit

# Run all integration tests
yarn test:integration

adapter=myadapter # Your adapter name, coinmarketcap, coingecko, etc

# Run integration tests for that adapter
yarn test $adapter/test/integration

# Run unit tests for that adapter
yarn test $adapter/test/unit

# Run a specific test for that adapter
yarn test $adapter/test/unit/my-specific-test.test.ts

# Run a tests in watch mode, re-running tests that have code changes or dependency changes in them
yarn test --watch $adapter/test/unit

Adding Integration Test Fixtures

We use nock for intercepting HTTP requests in integration tests and returning mock data. The recording functionality of nock is used when first writing the test to automatically generate accurate fixture data.

For example, take a look at the [synth-index] (./packages/composites/synth-index/test/integration/adapter.test.ts) test to see it in usage. When the RECORD environment variable is truthy, nock will proxy HTTP requests and generate fixture data that can be used to contruct the integration test.

The follow steps is the general pattern for writing an integration test.

1. Setup nock to record HTTP requests, see the [synth-index] (./packages/composites/synth-index/test/integration/adapter.test.ts) test for a code sample.
2. Run the test, using live API endpoints for the external adapter under test to hit, with nock recording on.
3. Using the generated fixture data from step 2, setup nock to now intercept HTTP requests and return mock data instead.
4. Now you should have a test that does not do any HTTP requests during execution.

For more information, see the Jest docs.