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Gofer CLI Readme

As in a tool that specializes in the delivery of special items.

Gofer is a tool that provides reliable asset prices taken from various sources.

If you need reliable price information, getting them from a single source is not the best idea. The data source may fail or provide incorrect data. Gofer solves this problem. With Gofer, you can define precise price models that specify exactly, from how many sources you want to pull prices and what conditions they must meet to be considered reliable.

Table of contents

Installation

To install it, you'll first need Go installed on your machine. Then you can use standard Go command: go get -u github.com/makerdao/oracle-suite/cmd/gofer.

Alternatively, you can build Gofer using Makefile directly from the repository. This approach is recommended if you wish to work on Gofer source.

git clone https://github.com/makerdao/oracle-suite.git
cd oracle-suite
make

Price models

To start working with Gofer, you have to define price models first. Price models are defined in a JSON file. By default, the default config file location is gofer.json in the current directory. You can change the config file location using the --config flag.

Simple price model for the BTC/USD asset pair may look like this:

{
  "gofer": {
    "priceModels": {
      "BTC/USD": {
        "method": "median",
        "sources": [
          [
            {
              "origin": "bitstamp",
              "pair": "BTC/USD",
              "ttl": 60
            }
          ]
        ],
        "params": {
          "minimumSuccessfulSources": 1
        }
      }
    }
  }
}

All price models must be defined under the priceModels key as a map where a key is an asset pair name written as XXX/YYY, where XXX is the base asset name and YYY is the quote asset name. These symbols are case-insensitive. The / as a separator is the only requirement here.

Price model for each asset pair consists of three keys: method, sources and params:

  • sources - contains a list of sources used to determine asset price. Each source must consist of one or more asset pairs. If multiple asset pairs are given, then the cross rate between them will be calculated. Each asset pair consists of two mandatory keys: origin, pair, and one optional: ttl (which is set to 60 by default).

    As stated earlier, multiple sources may be provided to calculate the cross rate between different assets. For example, to get BTC/JPY price, you may provide the following list of sources:

    [
  {"origin": "bitstamp", "pair": "BTC/USD"}, 
  {"origin": "fx", "pair": "USD/JPY"}
]

    To correctly calculate the cross rate, all adjacent pairs in a list must have a common asset.

  • params - usage depends on the value of the method field.

  • method - specifies the method used to calculate a single asset price from a given sources list. Currently, only the median method is supported:

    • median - calculates the median price from given sources. This method requires one parameter to be provided in the params field:
      • minimumSuccessfulSources - minimum number of successfully retrieved sources to consider calculated median price as reliable.

Origins configuration

Some origins might require additional configuration parameters like an API Key. In the current implementation, we have openexchangerates and coinmarketcap. Both of these origins require an API Key. To configure these origins we have to provide origins field in the configuration file.

Example:

{
  "gofer": {
    "origins": {
      "openexchangerates": {
        "type": "openexchangerates",
        "params": {
          "apiKey": "API_KEY"
        }
      }
    }
  }
}
  • type - this key corresponds to the built-in origin set
  • params - this object will map the params to the specific origin configuration (apiKey is one example)

Commands

Gofer is designed from the beginning to work with other programs, like oracle-v2. For this reason, by default, a response is returned as the NDJSON format. You can change the output format to plain, json , ndjson, or trace using the --format flag:

  • plain - simple, human-readable format with only basic information.
  • json - json array with list of results.
  • ndjson - same as json but instead of array, elements are returned in new lines.
  • trace - used to debug price models, prints a detailed graph with all possible information.

gofer price

The price command returns a price for one or more asset pairs. If no pairs are provided then prices for all asset pairs defined in the config file will be returned. When at least one price fails to be retrieved correctly, then the command returns a non-zero status code.

Return prices for given PAIRs.

Usage:
  gofer prices [PAIR...] [flags]

Aliases:
  prices, price

Flags:
  -h, --help   help for prices

Global Flags:
  -c, --config string                    config file (default "./gofer.json")
  -f, --format plain|trace|json|ndjson   output format (default ndjson)
      --log.format text|json             log format
  -v, --log.verbosity string             verbosity level (default "info")
      --norpc                            disable the use of RPC agent

JSON output for a single asset pair consists of the following fields:

  • type - may be aggregator or origin. The aggregator value means that a given price has been calculated based on other prices, the origin value is used when a price is returned directly from an origin.
  • base - the base asset name.
  • quote - the quote asset name.
  • price - the current asset price.
  • bid - the bid price, 0 if it is impossible to retrive or calculate bid price.
  • ask - the ask price, 0 if it is impossible to retrive or calculate ask price.
  • vol24 - the volume from last 24 hours, 0 if it is impossible to retrieve or calculate volume.
  • ts - the date from which the price was retrieved.
  • params - the list of additional parameters, it always contains the method field for aggregators and the origin field for origins.
  • error - the optional error message, if this field is present, then price is not relaiable.
  • price - the list of prices used in calculation. For origins it's always empty.

Example JSON output for BTC/USD pair:

{
   "type":"aggregator",
   "base":"BTC",
   "quote":"USD",
   "price":45242.13,
   "bid":45236.308,
   "ask":45239.98,
   "vol24h":0,
   "ts":"2021-05-18T10:30:00Z",
   "params":{
      "method":"median",
      "minimumSuccessfulSources":"3"
   },
   "prices":[
      {
         "type":"origin",
         "base":"BTC",
         "quote":"USD",
         "price":45227.05,
         "bid":45221.79,
         "ask":45227.05,
         "vol24h":8339.77051164,
         "ts":"2021-05-18T10:31:16Z",
         "params":{
            "origin":"bitstamp"
         }
      },
      {
         "type":"origin",
         "base":"BTC",
         "quote":"USD",
         "price":45242.13,
         "bid":45236.308,
         "ask":45240.468,
         "vol24h":0,
         "ts":"2021-05-18T10:31:18.687607Z",
         "params":{
            "origin":"bittrex"
         }
      }
   ]
}

Examples:

$ gofer price --format plain
BTC/USD 45291.110000
ETH/USD 3501.636879

$ gofer price BTC/USD --format trace
Price for BTC/USD:
───aggregator(method:median, minimumSuccessfulSources:3, pair:BTC/USD, price:45287.18, timestamp:2021-05-18T10:35:00Z)
   ├──origin(origin:bitstamp, pair:BTC/USD, price:45298.02, timestamp:2021-05-18T10:35:39Z)
   ├──origin(origin:bittrex, pair:BTC/USD, price:45287.18, timestamp:2021-05-18T10:35:43.335185Z)
   ├──origin(origin:coinbasepro, pair:BTC/USD, price:45282.53, timestamp:2021-05-18T10:35:43.285832Z)
   ├──origin(origin:gemini, pair:BTC/USD, price:45266.13, timestamp:2021-05-18T10:35:00Z)
   └──origin(origin:kraken, pair:BTC/USD, price:45291.2, timestamp:2021-05-18T10:35:43.470442Z)

gofer pairs

The pairs command can be used to check if there are defined price models for given pairs and also to debug existing price models. When the price model is missing, then the command returns a non-zero status code. If no pairs are provided then all asset pairs defined in the config file will be returned. In combination with the --format=trace flag, the command will return price models for given pairs.

List all supported asset pairs.

Usage:
  gofer pairs [PAIR...] [flags]

Aliases:
  pairs, pair

Flags:
  -h, --help   help for pairs

Global Flags:
  -c, --config string                    config file (default "./gofer.json")
  -f, --format plain|trace|json|ndjson   output format (default ndjson)
      --log.format text|json             log format
  -v, --log.verbosity string             verbosity level (default "info")
      --norpc                            disable the use of RPC agent

Examples:

$ gofer pairs
"BTC/USD"
"ETH/USD"

$ gofer pairs --format plain
BTC/USD
ETH/USD

$ gofer pair BTC/USD --format trace
Graph for BTC/USD:
───median(pair:BTC/USD)
   ├──origin(origin:bitstamp, pair:BTC/USD)
   ├──origin(origin:bittrex, pair:BTC/USD)
   ├──origin(origin:coinbasepro, pair:BTC/USD)
   ├──origin(origin:gemini, pair:BTC/USD)
   └──origin(origin:kraken, pair:BTC/USD)

gofer agent

The agent command runs Gofer in the agent mode.

Excessive use of the gofer price command may invoke many API calls to external services which can lead to rate-limiting. To avoid this, the prices that were previously retrieved can be reused and updated only as often as is defined in the ttl parameters. To do this, Gofer needs to be run in agent mode.

At first, the agent mode has to be enabled in the configuration file by adding the following field:

{
  "gofer": {
    "rpc": {
      "address": "127.0.0.1:8080"
    }
  }
}

The above address is used as the listen address for the internal RPC server and as a server address for a client. Next, you have to launch the agent using the gofer agent command.

From now, the gofer price command will retrieve asset prices from the agent instead of retrieving them directly from the origins. If you want to temporarily disable this behavior you have to use the --norpc flag.

Gofer library

Gofer can also be used as a library. Below you can find a simple example:

package main

import (
	"fmt"
	"time"

	"github.com/makerdao/oracle-suite/internal/query"

	"github.com/makerdao/oracle-suite/pkg/gofer"
	"github.com/makerdao/oracle-suite/pkg/gofer/graph"
	"github.com/makerdao/oracle-suite/pkg/gofer/graph/feeder"
	"github.com/makerdao/oracle-suite/pkg/gofer/graph/nodes"
	"github.com/makerdao/oracle-suite/pkg/gofer/origins"
	"github.com/makerdao/oracle-suite/pkg/log/null"
)

func main() {
	// Price model model for the BTC/USD pair:
	btcusd := gofer.Pair{Base: "BTC", Quote: "USD"}
	bitfinexBTCUSD := nodes.OriginPair{Origin: "bitfinex", Pair: btcusd}
	binanceBTCUSD := nodes.OriginPair{Origin: "binance", Pair: btcusd}
	medianNode := nodes.NewMedianAggregatorNode(btcusd, 2)
	medianNode.AddChild(nodes.NewOriginNode(bitfinexBTCUSD, time.Minute, 2*time.Minute))
	medianNode.AddChild(nodes.NewOriginNode(binanceBTCUSD, time.Minute, 2*time.Minute))
	m := map[gofer.Pair]nodes.Aggregator{btcusd: medianNode}

	const defaultWorkerCount = 5
	httpWorkerPool := query.NewHTTPWorkerPool(defaultWorkerCount)

	// Feeder is used to fetch prices:
	f := feeder.NewFeeder(origins.DefaultOriginSet(httpWorkerPool), null.New())

	// Initialize gofer and ask for BTC/USD price:
	g := graph.NewGofer(m, f)
	p, err := g.Price(btcusd)
	if err != nil {
		panic(err)
	}
	fmt.Printf("%s: %f", btcusd, p.Price)
}

The full documentation for Gofer library can be found here: https://pkg.go.dev/github.com/makerdao/oracle-suite/pkg/gofer

License

The GNU Affero General Public License