原创不易，转载请注明出处https://steemit.com/eos/@camphortree/eos-dpos
eos的出块流程大致如下：
Plain Text
........
//启动生产插件
producer_plugin::plugin_startup();
........
//出块循环
my->schedule_production_loop();
.........
//出块
auto result = start_block();
..........
//签名和提交
auto res = self->maybe_produce_block();
..........
此外：
// 下一次块的时间
const fc::time_point block_time = calculate_pending_block_time();
//
以上步骤的核心在于：auto result = start_block();
这个函数更跟下去会发现，重点在于：
Plain Text
chain.start_block(block_time, blocks_to_confirm);
这个函数才是dops的关键
void start_block( block_timestamp_type when, uint16_t confirm_block_count, controller::block_status s ) {
FC_ASSERT( !pending );
FC_ASSERT( db.revision() == head->block_num, "",
("db.revision()", db.revision())("controller_head_block", head->block_num)("fork_db_head_block", fork_db.head()->block_num) );
auto guard_pending = fc::make_scoped_exit([this](){
pending.reset();
});
pending = db.start_undo_session(true);
pending->_block_status = s;
//由当前区块头创建一个新的block_state ---->>>>> 11111
pending->_pending_block_state = std::make_shared<block_state>( *head, when ); // promotes pending schedule (if any) to active
pending->_pending_block_state->in_current_chain = true;
//确认链上的区块 ----->>>>> 22222
pending->_pending_block_state->set_confirmed(confirm_block_count);
//更新激活的生产者 ----->>>> 33333
auto was_pending_promoted = pending->_pending_block_state->maybe_promote_pending();
const auto& gpo = db.get<global_property_object>();
if( gpo.proposed_schedule_block_num.valid() && // if there is a proposed schedule that was proposed in a block ...
( *gpo.proposed_schedule_block_num <= pending->_pending_block_state->dpos_irreversible_blocknum ) && // ... that has now become irreversible ...
pending->_pending_block_state->pending_schedule.producers.size() == 0 && // ... and there is room for a new pending schedule ...
!was_pending_promoted // ... and not just because it was promoted to active at the start of this block, then:
)
{
// Promote proposed schedule to pending schedule.
if( !replaying ) {
ilog( "promoting proposed schedule (set in block ${proposed_num}) to pending; current block: ${n} lib: ${lib} schedule: ${schedule} ",
("proposed_num", *gpo.proposed_schedule_block_num)("n", pending->_pending_block_state->block_num)
("lib", pending->_pending_block_state->dpos_irreversible_blocknum)
("schedule", static_cast<producer_schedule_type>(gpo.proposed_schedule) ) );
}
pending->_pending_block_state->set_new_producers( gpo.proposed_schedule );
db.modify( gpo, [&]( auto& gp ) {
gp.proposed_schedule_block_num = optional<block_num_type>();
gp.proposed_schedule.clear();
});
std::cout<<"\n========555==========\n";
std::cout<< fc::json::to_string(*pending->_pending_block_state)<<"\n";
std::cout<<"==========555========\n";
}
11111,22222,33333这三步涉及到的数据结构是block_state
{
"id": "0000058af1b33d45e4ec927e52b74e8568422f45245dc0399c144bdff6dc16d8",
"block_num": 1418,
"header": {
"timestamp": "2018-08-04T07:31:47.500",
"producer": "accountnum33",
"confirmed": 0,
"previous": "0000058980ac0382075af4216ddbd7be1eae1690a278d7cc04a61570f307b39d",
"transaction_mroot": "0000000000000000000000000000000000000000000000000000000000000000",
"action_mroot": "eaadc508183ba966551e48dba3a44505a95e6a42d7a53f435db39c3dec3584c9",
"schedule_version": 1,
"header_extensions": [ ],
"producer_signature": "SIG_K1_KVyKdpLpEXPQUvRR5jZL4FMYvFDNic6tyvX6icLXFKhoriskCg21esduAceX2cZDv2GwcB12TxdneeKMwfzWB2TckZpZvQ"
},
"dpos_proposed_irreversible_blocknum": 1370,
"dpos_irreversible_blocknum": 1370,
"bft_irreversible_blocknum": 0,
"pending_schedule_lib_num": 1369,
"pending_schedule_hash": "b4ea72a3e20628a54028e681258cd1e6a46b20ae07210836f29087f9f8f37346",
"pending_schedule": {
"version": 1,
"producers": [ ]
},
"active_schedule": {
"version": 1,
"producers": [
{
"producer_name": "accountnum11",
"block_signing_key": "EOS8mUftJXepGzdQ2TaCduNuSPAfXJHf22uex4u41ab1EVv9EAhWt"
},
{
"producer_name": "accountnum22",
"block_signing_key": "EOS8mUftJXepGzdQ2TaCduNuSPAfXJHf22uex4u41ab1EVv9EAhWt"
},
{
"producer_name": "accountnum33",
"block_signing_key": "EOS8mUftJXepGzdQ2TaCduNuSPAfXJHf22uex4u41ab1EVv9EAhWt"
}
]
},
"blockroot_merkle": {
"_active_nodes": [
"0000058980ac0382075af4216ddbd7be1eae1690a278d7cc04a61570f307b39d",
"ab53f4807abffafbcf15fa6edd6ffe72cf73d18689403e389127015b4fd1e544",
"0275481b63dcb217603558835292d4057d39f9a5d41c9d5302230d379a992b18",
"af944001e02b80671b6ea50e5f83969fc2db5e56671ff83700a9018336d0fc58",
"e1ed7b7a82f5507110497fd41f2098a269ffbe8202de0f57393b4aeb27792434",
"5a36ca2325d5f7b2de22b98de7cf70c0a06cf391fc17f1d242b964d16146dee9"
],
"_node_count": 1417
},
"producer_to_last_produced": [
[
"accountnum11",
1394
],
[
"accountnum22",
1406
],
[
"accountnum33",
1418
],
[
"eosio",
1370
]
],
"producer_to_last_implied_irb": [
[
"accountnum11",
1370
],
[
"accountnum22",
1370
],
[
"accountnum33",
1370
]
],
"block_signing_key": "EOS8mUftJXepGzdQ2TaCduNuSPAfXJHf22uex4u41ab1EVv9EAhWt",
"confirm_count": [
2,
2,
2,
2,
2,
2,
2,
2,
2,
2,
2,
2,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
2,
2,
2,
2,
2,
2,
2,
2,
2,
2,
2,
2
],
"confirmations": [ ],
"block": {
"timestamp": "2018-08-04T07:31:47.500",
"producer": "accountnum33",
"confirmed": 0,
"previous": "0000058980ac0382075af4216ddbd7be1eae1690a278d7cc04a61570f307b39d",
"transaction_mroot": "0000000000000000000000000000000000000000000000000000000000000000",
"action_mroot": "eaadc508183ba966551e48dba3a44505a95e6a42d7a53f435db39c3dec3584c9",
"schedule_version": 1,
"header_extensions": [ ],
"producer_signature": "SIG_K1_KVyKdpLpEXPQUvRR5jZL4FMYvFDNic6tyvX6icLXFKhoriskCg21esduAceX2cZDv2GwcB12TxdneeKMwfzWB2TckZpZvQ",
"transactions": [ ],
"block_extensions": [ ]
},
"validated": true,
"in_current_chain": true
}
第一步：从当前块头出发，生成一个新的block_state。
........
result.producer_to_last_implied_irb[prokey.producer_name] = result.dpos_proposed_irreversible_blocknum;
result.dpos_irreversible_blocknum = result.calc_dpos_last_irreversible();
/// grow the confirmed count
static_assert(std::numeric_limits<uint8_t>::max() >= (config::max_producers * 2 / 3) + 1, "8bit confirmations may not be able to hold all of the needed confirmations");
// This uses the previous block active_schedule because thats the "schedule" that signs and therefore confirms _this_ block
auto num_active_producers = active_schedule.producers.size();
uint32_t required_confs = (uint32_t)(num_active_producers * 2 / 3) + 1;
if( confirm_count.size() < config::maximum_tracked_dpos_confirmations ) {
result.confirm_count.reserve( confirm_count.size() + 1 );
result.confirm_count = confirm_count;
result.confirm_count.resize( confirm_count.size() + 1 );
result.confirm_count.back() = (uint8_t)required_confs;
} else {
result.confirm_count.resize( confirm_count.size() );
memcpy( &result.confirm_count[0], &confirm_count[1], confirm_count.size() - 1 );
result.confirm_count.back() = (uint8_t)required_confs;
}
.......
当前3个生产节点，required_confs为3，所以11111结束后，confirm_count中会压入3，即当前出产块所需的确认个数。
下面直接给出几个解释：
confirm_count：区块所需确认个数表，从当前出产块往前推，最后的元素为当前出产块所需的确认个数
producer_to_last_implied_irb：由生产者确定的不可逆区块候选名单
dpos_irreversible_blocknum：不可逆区块
dpos_proposed_irreversible_blocknum：候选不可逆区块
active_schedule：已激活的生产者列表
有了对这几个定义的解释，代码变得很清晰
//计算不可逆区块，将不可逆区块候选名单中从小到大排，选出1/3处的区块号作为不可逆区块
uint32_t block_header_state::calc_dpos_last_irreversible()const {
vector<uint32_t> blocknums; blocknums.reserve( producer_to_last_implied_irb.size() );
for( auto& i : producer_to_last_implied_irb ) {
blocknums.push_back(i.second);
}
/// 2/3 must be greater, so if I go 1/3 into the list sorted from low to high, then 2/3 are greater
if( blocknums.size() == 0 ) return 0;
/// TODO: update to nth_element
std::sort( blocknums.begin(), blocknums.end() );
return blocknums[ (blocknums.size()-1) / 3 ];
}
上面的程序中出现两次3分之几的算法，第一次是required_confs，没毛病，一个区块要得到2/3个生产者的确认。但是得到2/3的确认与不可逆区块的联系不仅仅是这个，严格来说，不可逆区块是从不可逆区块候选名单中选择出来的。
第11111步之后的json
{
"id": "0000000000000000000000000000000000000000000000000000000000000000",
"block_num": 1419,
"header": {
"timestamp": "2018-08-04T07:31:48.000",
"producer": "accountnum11",
"confirmed": 1,
"previous": "0000058af1b33d45e4ec927e52b74e8568422f45245dc0399c144bdff6dc16d8",
"transaction_mroot": "0000000000000000000000000000000000000000000000000000000000000000",
"action_mroot": "0000000000000000000000000000000000000000000000000000000000000000",
"schedule_version": 1,
"header_extensions": [ ],
"producer_signature": "SIG_K1_111111111111111111111111111111111111111111111111111111111111111116uk5ne"
},
"dpos_proposed_irreversible_blocknum": 1370,
"dpos_irreversible_blocknum": 1370,
"bft_irreversible_blocknum": 0,
"pending_schedule_lib_num": 1369,
"pending_schedule_hash": "b4ea72a3e20628a54028e681258cd1e6a46b20ae07210836f29087f9f8f37346",
"pending_schedule": {
"version": 1,
"producers": [ ]
},
"active_schedule": {
"version": 1,
"producers": [
{
"producer_name": "accountnum11",
"block_signing_key": "EOS8mUftJXepGzdQ2TaCduNuSPAfXJHf22uex4u41ab1EVv9EAhWt"
},
{
"producer_name": "accountnum22",
"block_signing_key": "EOS8mUftJXepGzdQ2TaCduNuSPAfXJHf22uex4u41ab1EVv9EAhWt"
},
{
"producer_name": "accountnum33",
"block_signing_key": "EOS8mUftJXepGzdQ2TaCduNuSPAfXJHf22uex4u41ab1EVv9EAhWt"
}
]
},
"blockroot_merkle": {
"_active_nodes": [
"f8a83438724a996caaa42231c39b757bec3d1b6fb0bd2c982812eb2f7fadc377",
"ab53f4807abffafbcf15fa6edd6ffe72cf73d18689403e389127015b4fd1e544",
"0275481b63dcb217603558835292d4057d39f9a5d41c9d5302230d379a992b18",
"af944001e02b80671b6ea50e5f83969fc2db5e56671ff83700a9018336d0fc58",
"e1ed7b7a82f5507110497fd41f2098a269ffbe8202de0f57393b4aeb27792434",
"2553b9e4b8225b0f311c2a382fccd027e90f909319616b75933b56f19d20c440"
],
"_node_count": 1418
},
"producer_to_last_produced": [
[
"accountnum11",
1419
],
[
"accountnum22",
1406
],
[
"accountnum33",
1418
],
[
"eosio",
1370
]
],
"producer_to_last_implied_irb": [
[
"accountnum11",
1370
],
[
"accountnum22",
1370
],
[
"accountnum33",
1370
]
],
"block_signing_key": "EOS8mUftJXepGzdQ2TaCduNuSPAfXJHf22uex4u41ab1EVv9EAhWt",
"confirm_count": [
2,
2,
2,
2,
2,
2,
2,
2,
2,
2,
2,
2,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
2,
2,
2,
2,
2,
2,
2,
2,
2,
2,
2,
2,
3
],
"confirmations": [ ],
"block": {
"timestamp": "2018-08-04T07:31:48.000",
"producer": "accountnum11",
"confirmed": 1,
"previous": "0000058af1b33d45e4ec927e52b74e8568422f45245dc0399c144bdff6dc16d8",
"transaction_mroot": "0000000000000000000000000000000000000000000000000000000000000000",
"action_mroot": "0000000000000000000000000000000000000000000000000000000000000000",
"schedule_version": 1,
"header_extensions": [ ],
"producer_signature": "SIG_K1_111111111111111111111111111111111111111111111111111111111111111116uk5ne",
"transactions": [ ],
"block_extensions": [ ]
},
"validated": false,
"in_current_chain": false
}
到第22222步，这个函数确定了候选不可逆区与确认列表的关系
num_prev_blocks是指当前节点最后一次出块到现在的间隔，本文使用3个节点，故间隔为24
比如出块顺序为accountnum33--》accountnum11--》accountnum22--》accountnum33
accountnum33会把自己的块确认一次
accountnum11的时候会把33出过的块和自己确认一次。。。。
确认就是将confirmed数组的相应元素减去1，第一步得到的json中：
"confirm_count":[2,2,2,2,2,2,2,2,2,2,2,2,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,2,2,2,2,3]
此时num_prev_blocks = 24
所以以下程序的工作是先将confirm_count元素从尾到头减去1，最多遍历num_prev_blocks和confirm_count大小中最小的。
"confirm_count":[2,2,2,2,2,2,2,2,2,2,2,2,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,1,1,1,1,1,1,1,1,1,1,1,2]
由于出现了“0”元素，将0元素的区块号(1406)记录在dpos_proposed_irreversible_blocknum中，然后在更新数组，将0之前的元素去掉。
"confirm_count":[1,1,1,1,1,1,1,1,1,1,1,1,2]
所以这样看来，dpos_proposed_irreversible_blocknum就是本生产节点在本块确定的候选不可逆区块。而这个参数会在下一次出块时打包进producer_to_last_implied_irb。
void block_header_state::set_confirmed( uint16_t num_prev_blocks ) {
/*
idump((num_prev_blocks)(confirm_count.size()));
for( uint32_t i = 0; i < confirm_count.size(); ++i ) {
std::cerr << "confirm_count["<<i<<"] = " << int(confirm_count[i]) << "\n";
}
*/
header.confirmed = num_prev_blocks;
int32_t i = (int32_t)(confirm_count.size() - 1);
uint32_t blocks_to_confirm = num_prev_blocks + 1; /// confirm the head block too
while( i >= 0 && blocks_to_confirm ) {
--confirm_count[i];
//idump((confirm_count[i]));
if( confirm_count[i] == 0 )
{
uint32_t block_num_for_i = block_num - (uint32_t)(confirm_count.size() - 1 - i);
dpos_proposed_irreversible_blocknum = block_num_for_i;
//idump((dpos2_lib)(block_num)(dpos_irreversible_blocknum));
if (i == confirm_count.size() - 1) {
confirm_count.resize(0);
} else {
memmove( &confirm_count[0], &confirm_count[i + 1], confirm_count.size() - i - 1);
confirm_count.resize( confirm_count.size() - i - 1 );
}
return;
}
--i;
--blocks_to_confirm;
}
}
第22222步之后的输出json为：
{
"id": "0000000000000000000000000000000000000000000000000000000000000000",
"block_num": 1419,
"header": {
"timestamp": "2018-08-04T07:31:48.000",
"producer": "accountnum11",
"confirmed": 24,
"previous": "0000058af1b33d45e4ec927e52b74e8568422f45245dc0399c144bdff6dc16d8",
"transaction_mroot": "0000000000000000000000000000000000000000000000000000000000000000",
"action_mroot": "0000000000000000000000000000000000000000000000000000000000000000",
"schedule_version": 1,
"header_extensions": [ ],
"producer_signature": "SIG_K1_111111111111111111111111111111111111111111111111111111111111111116uk5ne"
},
"dpos_proposed_irreversible_blocknum": 1406,
"dpos_irreversible_blocknum": 1370,
"bft_irreversible_blocknum": 0,
"pending_schedule_lib_num": 1369,
"pending_schedule_hash": "b4ea72a3e20628a54028e681258cd1e6a46b20ae07210836f29087f9f8f37346",
"pending_schedule": {
"version": 1,
"producers": [ ]
},
"active_schedule": {
"version": 1,
"producers": [
{
"producer_name": "accountnum11",
"block_signing_key": "EOS8mUftJXepGzdQ2TaCduNuSPAfXJHf22uex4u41ab1EVv9EAhWt"
},
{
1,
1,
1,
1,
1,
1,
1,
1,
2
],
"confirmations": [ ],
"block": {
"timestamp": "2018-08-04T07:31:48.000",
"producer": "accountnum11",
"confirmed": 1,
"previous": "0000058af1b33d45e4ec927e52b74e8568422f45245dc0399c144bdff6dc16d8",
"transaction_mroot": "0000000000000000000000000000000000000000000000000000000000000000",
"action_mroot": "0000000000000000000000000000000000000000000000000000000000000000",
"schedule_version": 1,
"header_extensions": [ ],
"producer_signature": "SIG_K1_111111111111111111111111111111111111111111111111111111111111111116uk5ne",
"transactions": [ ],
"block_extensions": [ ]
},
"validated": false,
"in_current_chain": true
}
综上，实际上dpos在代码里面使用是分作两步的。
1，2/3共识，符合2/3认可的最高区块可以进入”由生产者确定的不可逆区块候选名单”。由于出块轮转，每个生产者所能见证的高度是不一样的。
2，1/3共识，从“由生产者确定的不可逆区块候选名单”中选择1/3高度的地方得到不可逆区块。
仔细一想，2还是加强了不可逆区块的共识。
