Constant EXTEND_LEASE_EVERY_MS 

pub const EXTEND_LEASE_EVERY_MS: u64 = 50; // 50u64

Period of time between two attempts to extend the lease. We’ll re-request a lease for an entire duration of LEASE_DURATION_MS milliseconds, every EXTEND_LEASE_EVERY_MS, so this has to be an amount safely low compared to LEASE_DURATION_MS, to make sure that we can miss a deadline without compromising the lock.