Emission Distribution
The Backstop contract is responsible for distributing emissions to backstop depositors and lending pools after it receives them from the emitter contract.
Reward Zone
Emissions are only distributed to pools in a reward_zone
, which the backstop contract manages, and backstop depositors designating their deposits to those pools.
Reward Zone Length
The number of pools that can be added to the reward zone starts at 10 and increases by one approximately every 3 months. This is done to prevent liquidity fragmentation by ensuring only a select number of pools receive emissions.
Adding Pools to the Reward Zone
Pools can be added to the Reward Zone by calling the add_reward()
function. This function intakes a potential pool to drop from the reward zone and attempts the addition with the following process:
If the pool being added to the reward zone has not met the minimum backstop threshold add_reward()
will fail.
If the to_remove pool is not in the reward zone, add_reward()
will fail.
If the pool is already in the reward zone, add_reward()
will fail.
Emission Management
The backstop contract facilitates both emission distribution and backstop emissions claims.
Emission Distribution
Emissions are distributed to backstop depositors and pools by calling the gulp_emissions()
function which:
Anyone may call gulp_emissions()
- it's expected that someone will run a bot to do so
Calculates the
new_emissions
received from the emitter whichequal to
emitter_last_distribution_time - backstop_last_distribution_time
At least one hour must have passed between emitter_last_distribution_time
and backstop_last_distribution_time
or this gulp_emissions()
will fail. This is to prevent rounding issues
Calculates the amount of emissions to allocate to backstop depositors and pools
Backstop depositors get 70% of new emissions
Pools get 30% of new emissions
Sets emissions per second for backstop depositors
equal to
(backstop_emissions * pool_backstop_tokens / total_backstop_tokens_in_reward_zone_pools) + remaining_emissions / 7 days)
This EPS will expire in 7 days, so emissions must be gulped every 7 days, or backstop depositors will stop receiving emissions until emissions are gulped again. Emissions not distributed during a gulp gap will be accrued in the next gulp call.
Backstop deposits queued for withdrawal will not count towards eithertotal_backstop_tokens_in_reward_zone_pools
or pool_backstop_tokens
in the emission distribution calculations
Sets emissions earned by each pool
equal to
pool_emissions * pool_backstop_tokens / total_backstop_tokens_in_reward_zone_pools
Emission Claims
The backstop facilitates emission claims by backstop depositors. Backstop depositors can claim their emissions by calling the claim()
function which transfers the user's earned emissions for all input pool addresses to the user and reduces the user's accrued emissions to 0.
All claimed emissions are automatically deposited into the backstop and allocated to the pool they were earned in.
Users can claim their emissions and deposit them on behalf of another user by specifying the user in the to
parameter in the claim()
function.
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