Overview

Keepers are meant participate in collateral, surplus and debt auctions by directly interacting with GEB auction contracts deployed to the Ethereum blockchain.

Keeper Responsibilities

The keepers are responsible with:

  1. Monitoring all active auctions

  2. Starting new auctions

  3. Discovering new auctions

  4. Ensuring a bidding model is running for each active auction

  5. Passing auction status to each bidding model

  6. Processing each bidding model output and submitting bids

Architecture

auction-keeper can read an auction's status directly from the Ethereum blockchain or from a Graph node. Its unique feature is the ability to plug in external bidding models which tell the keeper when and how much to bid. Bid prices are received from separate bidding models.

Bidding models are simple processes that can be implemented in any programming language. They only need to pass JSON objects to and from auction-keeper. The simplest example of a bidding model is a shell script which echoes a fixed price.

For every new block, all auctions from 1 to auctionsStarted are checked for active status. If a new auction is detected, a new bidding model is started.

NOTE: Bidding models are only used for surplus and debt auctions, not collateral auctions.

Installation

Examples:

Running on a host

Pre-requisites: Python 3.6+

Install auction-keeper dependencies with:

git clone https://github.com/reflexer-finance/auction-keeper.git
cd auction-keeper
git checkout tags/prai-demo
git submodule update --init --recursive
pip3 install -r requirements.txt

The keeper can now be run with bin/auction-keeper.

Auction specific examples:

Configuration Reference

Run bin/auction-keeper -h to see an up-to-date list of arguments and usage information.

General

--type collateral|surplus|debt A keeper can only participate in one type of auction

--collateral-type NAME If --type=collateral is passed, the collateral_type must also be provided. A keeper can only bid on a single collateral type auction at a time. NOTE: Currently, only the ETH-A collateral type is used.

--eth-from ADDRESS Address of the keeper. Warning: Do not use the same eth-from account on multiple keepers as it complicates SAFEEngine inventory management and will likely cause nonce conflicts. Using an eth-from account with an open SAFE is also discouraged.

--rpc-host HOST URI of ETH JSON-RPC node. Default "http://localhost:8545"

--rpc-timeout SECS Defaults to 10

The keeper connects to the Ethereum network using Web3.py and interacts with GEB using pyflex. A connection to an Ethereum node (--rpc-host) is required. Parity and Geth nodes are supported over HTTP. Websocket endpoints are not supported in pyflex. A full or archive node is required; light nodes are not supported.

If you don't want to run your own Ethereum node, third-party providers are available. This software has been tested with Infura, ChainSafe and QuikNode.

Gas price strategies

The following options determine the keeper's gas strategy and are mutually exclusive:

--ethgasstation-api-key MY_API_KEY Use ethgasstation.info for gas prices

--etherchain-gas-price Use etherchain.org for gas prices

--fixed-gas-price GWEI Use a fixed gas price (in GWEI)

If none of these options is given or if the gas API produces no result, the keeper will fetch the gas price from the node you connected to.

Other gas options

--gas-initial-multiplier MULTIPLIER When using an API source for fetching the initial gas price, this tunes the price. It's ignored when you're using --fixed-gas-price. In case no strategy is specified it defaults to 1.0

--gas-reactive-multiplier MULTIPLIER Every 30 seconds, a transaction's gas price will be multiplied by this value until it is mined or --gas-maxiumum is reached. Not used if gasPrice is passed from your bidding model. NOTE: Parity, as of this writing, requires a minimum gas increase of 1.125 to propagate a transaction replacement; this should be treated as a minimum value unless you want replacements to happen less frequently than 30 seconds (2+ blocks). This multiplier defaults to 1.125 if no other value is given.

--gas-maximum GWEI Maximum value for gas price

Accounting options

By default the keeper joins system coins to SAFEEngine on startup and exits all system coins and collateral upon shutdown. The keeper provides options for managing SAFEEngine balances, which may be turned off in case you'd like to manage balances manually.

--keep-system-coin-in-safe-engine-on-exit Do not exit system coin on shutdown

--keep-collateral-in-safe-engine-on-exit Do not exit collateral on shutdown

--return-collateral-interval SECS How often, in seconds, the keeper exits won collateral from SAFEEngine. Pass 0 to disable completely. Defaults to 300

--safe-engine-system-coin-target ALL|<integer> Amount of system coins the keeper will try to keep in SAFEEngine by rebalancing with joins and exits between its own wallet and its balance inside GEB. Defaults to ALL and the keeper will join all of an account's systems coins.

Rebalancing

System coins are rebalanced per --safe-engine-system-coin-target when:

  • The keeper starts up

  • SAFEEngine balance is insufficient in order to place a bid

  • An auction is settled

Rebalances do not account for system coins moved from the SAFEEngine to an auction contract for an active bid.

To avoid transaction spamming, small "dusty" system coins balances will be ignored (until the keeper exits, if so configured).

Managing resources

Retrieving SAFEs

To start collateral auctions, the keeper needs a list of SAFEs and the collateralization ratio of each safe. There are two ways to retrieve the list of open SAFEs:

--from-block BLOCK_NUMBER Scrape the chain for ModifySAFECollateralization events, starting at BLOCK_NUMBER . Set this to the block where the first ever SAFE was created. After startup, only new blocks will be queried. The scrape process can last a significant amount of time as the system matures. NOTE: To manage the performance of debt auction bidding, periodically adjust --from-block to the block number of the oldest liquidation which has not been popDebtFromQueued yet. Defaults to geb.starting_block_number, the block in which the system was deployed.

--graph-endpoints NODE1,NODE2 Comma delimited list of Graph endpoints used to retrieve ModifySAFECollateralization events. If multiple endpoints are passed, they will be pinged sequentially in the order they were specified in case one or many of them fail. NOTE: This flag is only supported for collateral auctions.

--graph-block-threshold NUMBER_OF_BLOCKS When the keeper fetches SAFE data to find critical safes, use the --graph-endpoints when the keeper's last processed block is older than NUMBER_OF_BLOCKS. The graph will be faster than a node when fetching historical data, but recent graph blocks might be slightly delayed compared to an ethereum node. This allows the keeper to to fetch historical data from the graph, but use the node for all newer blocks. Defaults to 20

The following are the most recent Graph node endpoints for RAI:--graph-endpoints https://subgraph.reflexer.finance/subgraphs/name/reflexer-labs/prai,https://api.thegraph.com/subgraphs/name/reflexer-labs/prai-mainnet

Auctions

--min-auction AUCTION_ID Ignore auctions older than AUCTION_ID

--max-auctions NUMBER Limit the number of bidding models created to handle active auctions.

--block-check-interval <integer>, default:1 How often the keeper checks for new blocks

--bid-check-interval <integer>, default 4 How often the keeper checks model processes for new bids

NOTE: if you'd like to use Infura with your keeper and prefer the free-tier (you do less than 100K requests per day), --block-check-interval must be greater than 10 and --bid-check-interval must be greater than 180. However, this will make your keeper slower and it will not quickly bid in auctions.

Flash swaps

Flash swaps allow a keeper to participate in collateral auctions without any system coins. The flash swap borrows the system coin necessary for the collateral auctions, wins the collateral at a discount and transferred the won collateral back to the keeper, all in one transaction. Note: If the overall transaction is not profitable, the swap will fail. The the keeper only needs enough ether to pay for the gas of the swap.

--flash-swap Turn on Uniswap flash swaps for collateral auctions. Not supported for --type debt or --type surplus

Sharding/Settling

Bid management can be sharded across multiple keepers. If you want to proceed with sharding, set these options:

--shards NUMBER_OF_KEEPER Number of keepers you plan to run. You must set this for all keepers

--shard-id SHARD_ID You must specify this for every keeper, counting from 0

For example, to configure three keepers, set --shards 3 and assign --shard-id 0, --shard-id 1, --shard-id 2 for the first, second and third keeper.

NOTE: Auction starts are not sharded. Only one keeper should be configured to liquidateSAFEs and this way startAuctions.

If you are sharding across multiple accounts, you may want to have a separate keeper that handles all your settleAuctions (in the case of English collateral, debt and surplus auctions)

--settle-for <ACCOUNT1 ACCOUNT2>|NONE|ALL Space-delimited list of accounts for which the keeper will settle auctions. Specify NONE to disable this option. If you'd like to donate your gas to settle auctions for all participants, ALL is also supported. Defaults to only the keeper address.

NOTE: Auction settlements are already sharded, so you should remove the sharding configuration if you're running a dedicated auction settlement keeper.

Transaction management

--bid-delay FLOAT

Many pending transactions can fill up the keeper's transaction queue, causing every subsequent transaction to be dropped. By waiting a small --bid-delay after each bid, multiple transactions can be submitted asynchronously while still allowing some time for older transactions to complete, freeing up the queue.

Many parameters determine the appropriate bid delay. For illustration purposes, assume the queue can hold 12 transactions, and gas prices are reasonable. In this setup, a bid delay of 1.2 seconds might provide ample time for transactions at the front of the queue to complete.

Limitations

  • If an auction started before the keeper was started, this keeper will not participate in it until the next block is mined

  • This keeper does not explicitly handle Global Settlement, and may submit transactions which fail during shutdown

  • Some keeper functions incur gas fees regardless of whether a bid is submitted. This includes, but is not limited to, the following actions:

    • submitting token approvals

    • adjusting the surplus and debt balances from AccountingEngine

    • liquidating a SAFE or starting a surplus or debt auction

  • The keeper does not check model prices until an auction exists. When configured to create new auctions, it will liquidateSAFEs or start a new surplus or debt auction regardless of whether or not your system coin or protocol token balance is sufficient to bid

  • Liquidating a SAFE to start a new collateral auction is a time consuming operation. To do so without a subgraph subscription, the keeper initializes a cache of SAFEs states by scraping event logs from the chain. The keeper will then continuously refresh SAFE states and detect undercollateralized SAFEs.

    • Despite batching log queries into multiple requests, Geth nodes are generally unable to initialize the SAFE state cache in a reasonable amount of time. As such, Geth is not recommended for liquidating SAFEs

    • To manage resources, it is recommended to run separate keepers using separate accounts to liquidate (--start-auctions-only) and bid (--bid-only) in auctions

For some known Ubuntu and macOS issues see the pyflex README.

Testing

This project uses pytest for unit testing. Testing depends on a dockerized local testchain included in lib\pyflex\tests\config.

In order to be able to run tests you should execute:

git clone https://github.com/reflexer-labs/auction-keeper.git
cd auction-keeper
git checkout tags/prai-demo
git submodule update --init --recursive
./install.sh
source _virtualenv/bin/activate
pip3 install -r requirements-dev.txt

You can then run all tests with:

./test.sh