Once the block that contains the proposal becomes irreversible, the schedule is promoted to "pending" automatically. Once the block that promotes the schedule is irreversible, the schedule will become "active" ?
(Question brought over from @the_dragon_master on Telegram)
The EOSIO consensus process consists of two parts:
These two processes are independent and can be executed in parallel, except for the very first schedule round after the boot sequence when the blockchain’s first genesis block is created.
The voting of the active producers to be included in the next schedule is implemented by the DPoS layer. Strictly speaking, a token holder must first stake some tokens to become a stakeholder and thus be able to vote with a given staking power.
After the producers are voted on and selected for the next schedule, they are simply sorted alphabetically by producer name. This determines the production order. Each producer receives the proposed set of producers for the next schedule round within the very first block to be validated from the current schedule round that is about to start. When the first block that contains the proposed schedule is deemed irreversible by a supermajority of producers plus one, the proposed schedule becomes active for the next schedule round.
The EOSIO block production schedule is divided equally among the elected producers. The producers are scheduled to produce an expected number of blocks each schedule round, based on the following parameters (per schedule round):
Parameter | Description | Default | Layer -|-|-|- P (producers) | number of active producers | 21 | 2 Bp (blocks/producer) | number of contiguous blocks per producer | 12 | 1 Tb (s/block) | Production time per block (s: seconds) | 0.5 | 1
It is important to mention that Bp (number of contiguous blocks per producer), and Tb (production time per block) are layer 1 consensus constants. In contrast, P (number of active producers) is a layer 2 constant configured by the DPoS layer, which is enabled by WASM contracts.
The following variables can be defined from the above parameters (per schedule round):
Variable | Description | Equation -|-|- B (blocks) | Total number of blocks | Bp (blocks/producer) x P (producers) Tp (s/producer) | Production time per producer | Tb (s/block) x Bp (blocks/producer) T (s) | Total production time | Tp (s/producer) x P (producers)
Therefore, the value of P, being defined at layer 2, can change dynamically in an EOSIO blockchain. In practice, however, N is strategically set to 21 producers, which means that 15 producers are required for a two-thirds supermajority of producers plus one to reach consensus.
With the current defaults: P=21 elected producers, Bp=12 blocks created per producer, and a block produced every T=0.5 seconds, current production times are as follows (per schedule round):
Variable | Value -|- Tp: Production time per producer | Tp = 0.5 (s/block) x 12 (blocks/producer) ⇒ Tp = 6 (s/producer) T: Total production time | T = 6 (s/producer) x 21 (producers) ⇒ T = 126 (s)
When a block is not produced by a given producer during its assigned time slot, a gap results in the blockchain.
(Answer taken from https://developers.eos.io/welcome/latest/protocol/consensus_protocol#42-producers-schedule)