3. push_transaction代码分析
这里我们来分析下push_transaction的过程，作为执行trx的入口，这个函数在EOS中非常重要，另一方面，这里EOS与Eosforce有一定区别，这里会具体介绍。
TODO 需要一个流程图，不过博客还不支持
3.1 transaction_metadata
我们先来看下push_transaction的transaction_metadata参数， 这个参数统一了各种不同类型，不同行为的trx：
/**
* This data structure should store context-free cached data about a transaction such as
* packed/unpacked/compressed and recovered keys
*/
class transaction_metadata {
public:
transaction_id_type id; // trx ID
transaction_id_type signed_id; // signed trx ID
signed_transaction trx;
packed_transaction packed_trx;
optional<pair<chain_id_type, flat_set<public_key_type>>> signing_keys;
bool accepted = false; // 标注是否调用了accepted信号，确保只调用一次
bool implicit = false; // 是否忽略检查
bool scheduled = false; // 是否是延迟trx
explicit transaction_metadata( const signed_transaction& t, packed_transaction::compression_type c = packed_transaction::none )
:trx(t),packed_trx(t, c) {
id = trx.id();
//raw_packed = fc::raw::pack( static_cast<const transaction&>(trx) );
signed_id = digest_type::hash(packed_trx);
}
explicit transaction_metadata( const packed_transaction& ptrx )
:trx( ptrx.get_signed_transaction() ), packed_trx(ptrx) {
id = trx.id();
//raw_packed = fc::raw::pack( static_cast<const transaction&>(trx) );
signed_id = digest_type::hash(packed_trx);
}
const flat_set<public_key_type>& recover_keys( const chain_id_type& chain_id );
uint32_t total_actions()const { return trx.context_free_actions.size() + trx.actions.size(); }
};
using transaction_metadata_ptr = std::shared_ptr<transaction_metadata>;
先看一下implicit，这个参数指示下面的逻辑是否要忽略对于trx的各种检查，一般用于系统内部的trx， 对于EOS，主要是处理on_block_transaction（可以参见出块文档），在start_block调用：
...autoonbtrx =std::make_shared( get_on_block_transaction() ); onbtrx->implicit =true;// on_block trx 会被无条件接受autoreset_in_trx_requiring_checks = fc::make_scoped_exit([old_value=in_trx_requiring_checks,this](){ in_trx_requiring_checks = old_value; }); in_trx_requiring_checks =true;// 修改in_trx_requiring_checks变量达到不将trx写入区块，一些系统的trx没有必要写入区块。push_transaction( onbtrx, fc::time_point::maximum(), self.get_global_properties().configuration.min_transaction_cpu_usage,true);...
!> Eosforce不同之处
而对于EOSForce中，除了on_block action之外，onfee合约也是被设置为implicit==true的，onfee合约是eosforce的系统合约，设计用来收取交易的手续费。
3.2 push_transaction函数
下面我们逐行分析下代码，EOS中push_transaction代码如下：
/**
* This is the entry point for new transactions to the block state. It will check authorization and
* determine whether to execute it now or to delay it. Lastly it inserts a transaction receipt into
* the pending block.
*/transaction_trace_ptrpush_transaction(consttransaction_metadata_ptr& trx, fc::time_point deadline,uint32_tbilled_cpu_time_us,boolexplicit_billed_cpu_time =false){// deadline必须不为空// deadline是trx执行时间的一个大上限，为了防止某些trx运行时间过长导致出块失败等问题，// 这里必须有一个严格的上限，一旦超过上限，交易会立即失败。EOS_ASSERT(deadline != fc::time_point(), transaction_exception,"deadline cannot be uninitialized"); transaction_trace_ptr trace;// trace主要用来保存执行中的一些错误信息。try{// trx_context是执行trx的上下文状态，下面会专门说明transaction_contexttrx_context(self, trx->trx, trx->id);if((bool)subjective_cpu_leeway && pending->_block_status == controller::block_status::incomplete) { trx_context.leeway = *subjective_cpu_leeway; }// 设置数据trx_context.deadline = deadline; trx_context.explicit_billed_cpu_time = explicit_billed_cpu_time; trx_context.billed_cpu_time_us = billed_cpu_time_us; trace = trx_context.trace;try{if( trx->implicit ) {// 如果是implicit的就没有必要做下面的一些检查和记录，这里的检查主要是资源方面的trx_context.init_for_implicit_trx(); trx_context.can_subjectively_fail =false; }else{// 如果是重放并且不是重放过程中接到的新交易，则不去使用`record_transaction`记录boolskip_recording = replay_head_time && (time_point(trx->trx.expiration) <= *replay_head_time);// 一些trx_context的初始化操作trx_context.init_for_input_trx( trx->packed_trx.get_unprunable_size(), trx->packed_trx.get_prunable_size(), trx->trx.signatures.size(), skip_recording); }if( trx_context.can_subjectively_fail && pending->_block_status == controller::block_status::incomplete ) { check_actor_list( trx_context.bill_to_accounts );// Assumes bill_to_accounts is the set of actors authorizing the transaction} trx_context.delay = fc::seconds(trx->trx.delay_sec);if( !self.skip_auth_check() && !trx->implicit ) {// 检测交易所需要的权限authorization.check_authorization( trx->trx.actions, trx->recover_keys( chain_id ), {}, trx_context.delay, [](){}/*std::bind(&transaction_context::add_cpu_usage_and_check_time, &trx_context,
std::placeholders::_1)*/,false); }// 执行，注意这时trx_context包括所有信息和状态trx_context.exec(); trx_context.finalize();// Automatically rounds up network and CPU usage in trace and bills payers if successfulautorestore = make_block_restore_point();if(!trx->implicit) {// 如果是非implicit的交易，则需要进入区块。transaction_receipt::status_enum s = (trx_context.delay == fc::seconds(0)) ? transaction_receipt::executed : transaction_receipt::delayed; trace->receipt = push_receipt(trx->packed_trx, s, trx_context.billed_cpu_time_us, trace->net_usage); pending->_pending_block_state->trxs.emplace_back(trx); }else{// 注意，这里implicit类的交易是不会进入区块的，只会计入资源消耗// 因为这类的trx无条件运行，所以不需要另行记录。transaction_receipt_header r; r.status = transaction_receipt::executed; r.cpu_usage_us = trx_context.billed_cpu_time_us; r.net_usage_words = trace->net_usage /8; trace->receipt = r; }// 这里会将执行过的action写入待出块状态的_actions之中fc::move_append(pending->_actions, move(trx_context.executed));// call the accept signal but only once for this transaction// 为这个交易调用accept信号，保证只调用一次if(!trx->accepted) { trx->accepted =true; emit( self.accepted_transaction, trx); }// 触发applied_transaction信号emit(self.applied_transaction, trace);if( read_mode != db_read_mode::SPECULATIVE && pending->_block_status == controller::block_status::incomplete ) {//this may happen automatically in destructor, but I prefere make it more explicittrx_context.undo(); }else{ restore.cancel(); trx_context.squash(); }// implicit的trx压根没有在unapplied_transactions中if(!trx->implicit) { unapplied_transactions.erase( trx->signed_id ); }returntrace; }catch(constfc::exception& e) { trace->except = e; trace->except_ptr =std::current_exception(); }// 注意这里，如果成功的话上面就返回了这里是失败的情况// failure_is_subjective 表明if(!failure_is_subjective(*trace->except)) { unapplied_transactions.erase( trx->signed_id ); } emit( self.accepted_transaction, trx ); emit( self.applied_transaction, trace );returntrace; } FC_CAPTURE_AND_RETHROW((trace)) }/// push_transaction
上面注释中阐述了大致的流程，下面仔细分析一下：
首先是trx_context，这个对象的类声明如下：
classtransaction_context{...// 省略voiddispatch_action( action_trace& trace,constaction& a, account_name receiver,boolcontext_free =false,uint32_trecurse_depth =0);inlinevoiddispatch_action( action_trace& trace,constaction& a,boolcontext_free =false){ dispatch_action(trace, a, a.account, context_free); };voidschedule_transaction();voidrecord_transaction(consttransaction_id_type& id, fc::time_point_sec expire );voidvalidate_cpu_usage_to_bill(int64_tu,boolcheck_minimum =true)const;public: controller& control;// controller类的引用constsigned_transaction& trx;// 要执行的trxtransaction_id_type id; optional undo_session; transaction_trace_ptr trace;// 记录错误的tracefc::time_point start;// 起始时刻fc::time_point published;// publish的时刻vector executed;// 执行完成的actionflat_set bill_to_accounts; flat_set validate_ram_usage;/// the maximum number of virtual CPU instructions of the transaction that can be safely billed to the billable accountsuint64_tinitial_max_billable_cpu =0; fc::microseconds delay;boolis_input =false;boolapply_context_free =true;boolcan_subjectively_fail =true; fc::time_point deadline = fc::time_point::maximum(); fc::microseconds leeway = fc::microseconds(3000);int64_tbilled_cpu_time_us =0;boolexplicit_billed_cpu_time =false;private:boolis_initialized =false;uint64_tnet_limit =0;boolnet_limit_due_to_block =true;boolnet_limit_due_to_greylist =false;uint64_teager_net_limit =0;uint64_t& net_usage;/// reference to trace->net_usageboolcpu_limit_due_to_greylist =false; fc::microseconds initial_objective_duration_limit; fc::microseconds objective_duration_limit; fc::time_point _deadline = fc::time_point::maximum();int64_tdeadline_exception_code = block_cpu_usage_exceeded::code_value;int64_tbilling_timer_exception_code = block_cpu_usage_exceeded::code_value; fc::time_point pseudo_start; fc::microseconds billed_time; fc::microseconds billing_timer_duration_limit; };
我们先看一下init_for_input_trx：
voidtransaction_context::init_for_input_trx(uint64_tpacked_trx_unprunable_size,// 这个是指trx打包后完整的大小uint64_tpacked_trx_prunable_size,// 这个指trx额外信息的大小uint32_tnum_signatures,// 这个参数没用上boolskip_recording )// 是否要跳过记录{// 根据cfg和trx初始化资源constauto& cfg = control.get_global_properties().configuration;// 利用packed_trx_unprunable_size和packed_trx_prunable_size 计算net资源消耗uint64_tdiscounted_size_for_pruned_data = packed_trx_prunable_size;if( cfg.context_free_discount_net_usage_den >0&& cfg.context_free_discount_net_usage_num < cfg.context_free_discount_net_usage_den ) { discounted_size_for_pruned_data *= cfg.context_free_discount_net_usage_num; discounted_size_for_pruned_data = ( discounted_size_for_pruned_data + cfg.context_free_discount_net_usage_den -1) / cfg.context_free_discount_net_usage_den;// rounds up}uint64_tinitial_net_usage =static_cast(cfg.base_per_transaction_net_usage) + packed_trx_unprunable_size + discounted_size_for_pruned_data;// 对于delay trx需要额外的net资源if( trx.delay_sec.value >0) {// If delayed, also charge ahead of time for the additional net usage needed to retire the delayed transaction// whether that be by successfully executing, soft failure, hard failure, or expiration.initial_net_usage +=static_cast(cfg.base_per_transaction_net_usage) +static_cast(config::transaction_id_net_usage); }// 初始化一些信息published = control.pending_block_time(); is_input =true;if(!control.skip_trx_checks()) { control.validate_expiration(trx); control.validate_tapos(trx); control.validate_referenced_accounts(trx); } init( initial_net_usage);// 这里调用init函数， 在这个函数中会处理cpu资源和ram资源if(!skip_recording)// 将trx添加入记录中record_transaction( id, trx.expiration );/// checks for dupes}
这里会先计算net，再在init函数中处理其他资源：
voidtransaction_context::init(uint64_tinitial_net_usage) { EOS_ASSERT( !is_initialized, transaction_exception,"cannot initialize twice");conststaticint64_tlarge_number_no_overflow =std::numeric_limits::max()/2;constauto& cfg = control.get_global_properties().configuration;auto& rl = control.get_mutable_resource_limits_manager(); net_limit = rl.get_block_net_limit(); objective_duration_limit = fc::microseconds( rl.get_block_cpu_limit() ); _deadline = start + objective_duration_limit;// Possibly lower net_limit to the maximum net usage a transaction is allowed to be billedif( cfg.max_transaction_net_usage <= net_limit ) { net_limit = cfg.max_transaction_net_usage; net_limit_due_to_block =false; }// Possibly lower objective_duration_limit to the maximum cpu usage a transaction is allowed to be billedif( cfg.max_transaction_cpu_usage <= objective_duration_limit.count() ) { objective_duration_limit = fc::microseconds(cfg.max_transaction_cpu_usage); billing_timer_exception_code = tx_cpu_usage_exceeded::code_value; _deadline = start + objective_duration_limit; }// Possibly lower net_limit to optional limit set in the transaction headeruint64_ttrx_specified_net_usage_limit =static_cast(trx.max_net_usage_words.value) *8;if( trx_specified_net_usage_limit >0&& trx_specified_net_usage_limit <= net_limit ) { net_limit = trx_specified_net_usage_limit; net_limit_due_to_block =false; }// Possibly lower objective_duration_limit to optional limit set in transaction headerif( trx.max_cpu_usage_ms >0) {autotrx_specified_cpu_usage_limit = fc::milliseconds(trx.max_cpu_usage_ms);if( trx_specified_cpu_usage_limit <= objective_duration_limit ) { objective_duration_limit = trx_specified_cpu_usage_limit; billing_timer_exception_code = tx_cpu_usage_exceeded::code_value; _deadline = start + objective_duration_limit; } } initial_objective_duration_limit = objective_duration_limit;if( billed_cpu_time_us >0)// could also call on explicit_billed_cpu_time but it would be redundantvalidate_cpu_usage_to_bill( billed_cpu_time_us,false);// Fail early if the amount to be billed is too high// Record accounts to be billed for network and CPU usagefor(constauto& act : trx.actions ) {for(constauto& auth : act.authorization ) { bill_to_accounts.insert( auth.actor ); } } validate_ram_usage.reserve( bill_to_accounts.size() );// Update usage values of accounts to reflect new timerl.update_account_usage( bill_to_accounts, block_timestamp_type(control.pending_block_time()).slot );// Calculate the highest network usage and CPU time that all of the billed accounts can afford to be billedint64_taccount_net_limit =0;int64_taccount_cpu_limit =0;boolgreylisted_net =false, greylisted_cpu =false;std::tie( account_net_limit, account_cpu_limit, greylisted_net, greylisted_cpu) = max_bandwidth_billed_accounts_can_pay(); net_limit_due_to_greylist |= greylisted_net; cpu_limit_due_to_greylist |= greylisted_cpu; eager_net_limit = net_limit;// Possible lower eager_net_limit to what the billed accounts can pay plus some (objective) leewayautonew_eager_net_limit =std::min( eager_net_limit,static_cast(account_net_limit + cfg.net_usage_leeway) );if( new_eager_net_limit < eager_net_limit ) { eager_net_limit = new_eager_net_limit; net_limit_due_to_block =false; }// Possibly limit deadline if the duration accounts can be billed for (+ a subjective leeway) does not exceed current deltaif( (fc::microseconds(account_cpu_limit) + leeway) <= (_deadline - start) ) { _deadline = start + fc::microseconds(account_cpu_limit) + leeway; billing_timer_exception_code = leeway_deadline_exception::code_value; } billing_timer_duration_limit = _deadline - start;// Check if deadline is limited by caller-set deadline (only change deadline if billed_cpu_time_us is not set)if( explicit_billed_cpu_time || deadline < _deadline ) { _deadline = deadline; deadline_exception_code = deadline_exception::code_value; }else{ deadline_exception_code = billing_timer_exception_code; } eager_net_limit = (eager_net_limit/8)*8;// Round down to nearest multiple of word size (8 bytes) so check_net_usage can be efficientif( initial_net_usage >0) add_net_usage( initial_net_usage );// Fail early if current net usage is already greater than the calculated limitchecktime();// Fail early if deadline has already been exceededis_initialized =true; }
以上就是transaction_context初始化过程，这里主要是处理资源消耗。
下面是exec函数，这个函数很简单：
voidtransaction_context::exec() { EOS_ASSERT( is_initialized, transaction_exception,"must first initialize");// 调用`dispatch_action`，这里并没有对上下文无关trx进行特别的操作，只是参数不同if( apply_context_free ) {for(constauto& act : trx.context_free_actions ) { trace->action_traces.emplace_back(); dispatch_action( trace->action_traces.back(), act,true); } }if( delay == fc::microseconds() ) {for(constauto& act : trx.actions ) { trace->action_traces.emplace_back(); dispatch_action( trace->action_traces.back(), act ); } }else{// 对于延迟交易，这里特别处理schedule_transaction(); } }
主要执行在dispatch_action中，这里会根据action不同分别触发对应的调用：
voidtransaction_context::dispatch_action( action_trace& trace,constaction& a, account_name receiver,boolcontext_free,uint32_trecurse_depth ) {// 构建apply_context执行action， apply_context的分析在下节进行apply_contextacontext( control, *this, a, recurse_depth ); acontext.context_free = context_free; acontext.receiver = receiver;try{ acontext.exec(); }catch( ... ) { trace = move(acontext.trace);throw; }// 汇总结果到tracetrace = move(acontext.trace); }
对于延迟交易，执行schedule_transaction：
voidtransaction_context::schedule_transaction() {// 因为交易延迟执行，会消耗额外的net和ram资源// Charge ahead of time for the additional net usage needed to retire the delayed transaction// whether that be by successfully executing, soft failure, hard failure, or expiration.if( trx.delay_sec.value ==0) {// Do not double bill. Only charge if we have not already charged for the delay.constauto& cfg = control.get_global_properties().configuration; add_net_usage(static_cast(cfg.base_per_transaction_net_usage) +static_cast(config::transaction_id_net_usage) );// Will exit early if net usage cannot be payed.}autofirst_auth = trx.first_authorizor();// 将延迟交易写入节点运行时状态数据库中，到时会从这里查找出来执行uint32_ttrx_size =0;constauto& cgto = control.db().create( [&](auto& gto ) { gto.trx_id = id; gto.payer = first_auth; gto.sender = account_name();/// delayed transactions have no sendergto.sender_id = transaction_id_to_sender_id( gto.trx_id ); gto.published = control.pending_block_time(); gto.delay_until = gto.published + delay; gto.expiration = gto.delay_until + fc::seconds(control.get_global_properties().configuration.deferred_trx_expiration_window); trx_size = gto.set( trx ); });// 因为要写内存记录，所以也消耗了一定的ramadd_ram_usage( cgto.payer, (config::billable_size_v + trx_size) ); }
调用完exec之后会调用transaction_context::finalize()：
// 这里主要是处理资源消耗voidtransaction_context::finalize() { EOS_ASSERT( is_initialized, transaction_exception,"must first initialize");if( is_input ) {auto& am = control.get_mutable_authorization_manager();for(constauto& act : trx.actions ) {for(constauto& auth : act.authorization ) { am.update_permission_usage( am.get_permission(auth) ); } } }auto& rl = control.get_mutable_resource_limits_manager();for(autoa : validate_ram_usage ) { rl.verify_account_ram_usage( a ); }// Calculate the new highest network usage and CPU time that all of the billed accounts can afford to be billedint64_taccount_net_limit =0;int64_taccount_cpu_limit =0;boolgreylisted_net =false, greylisted_cpu =false;std::tie( account_net_limit, account_cpu_limit, greylisted_net, greylisted_cpu) = max_bandwidth_billed_accounts_can_pay(); net_limit_due_to_greylist |= greylisted_net; cpu_limit_due_to_greylist |= greylisted_cpu;// Possibly lower net_limit to what the billed accounts can payif(static_cast(account_net_limit) <= net_limit ) {//NOTE:net_limit may possibly not be objective anymore due to net greylisting, but it should still be no greater than the truly objective net_limitnet_limit =static_cast(account_net_limit); net_limit_due_to_block =false; }// Possibly lower objective_duration_limit to what the billed accounts can payif( account_cpu_limit <= objective_duration_limit.count() ) {//NOTE:objective_duration_limit may possibly not be objective anymore due to cpu greylisting, but it should still be no greater than the truly objective objective_duration_limitobjective_duration_limit = fc::microseconds(account_cpu_limit); billing_timer_exception_code = tx_cpu_usage_exceeded::code_value; } net_usage = ((net_usage +7)/8)*8;// Round up to nearest multiple of word size (8 bytes)eager_net_limit = net_limit; check_net_usage();autonow = fc::time_point::now(); trace->elapsed = now - start; update_billed_cpu_time( now ); validate_cpu_usage_to_bill( billed_cpu_time_us ); rl.add_transaction_usage( bill_to_accounts,static_cast(billed_cpu_time_us), net_usage, block_timestamp_type(control.pending_block_time()).slot );// Should never fail}
接下来make_block_restore_point，这里添加了一个检查点：
// The returned scoped_exit should not exceed the lifetime of the pending which existed when make_block_restore_point was called.fc::scoped_exit> make_block_restore_point() {autoorig_block_transactions_size = pending->_pending_block_state->block->transactions.size();autoorig_state_transactions_size = pending->_pending_block_state->trxs.size();autoorig_state_actions_size = pending->_actions.size();std::function callback = [this, orig_block_transactions_size, orig_state_transactions_size, orig_state_actions_size]() { pending->_pending_block_state->block->transactions.resize(orig_block_transactions_size); pending->_pending_block_state->trxs.resize(orig_state_transactions_size); pending->_actions.resize(orig_state_actions_size); };returnfc::make_scoped_exit(std::move(callback) ); }
而后对于不是implicit的交易会调用push_receipt，这里会将trx写入区块数据中，这也意味着implicit为true的交易虽然执行了，但不会在区块中。
/**
* Adds the transaction receipt to the pending block and returns it.
*/templateconsttransaction_receipt&push_receipt(constT& trx, transaction_receipt_header::status_enum status,uint64_tcpu_usage_us,uint64_tnet_usage ){uint64_tnet_usage_words = net_usage /8; EOS_ASSERT( net_usage_words*8== net_usage, transaction_exception,"net_usage is not divisible by 8"); pending->_pending_block_state->block->transactions.emplace_back( trx ); transaction_receipt& r = pending->_pending_block_state->block->transactions.back(); r.cpu_usage_us = cpu_usage_us; r.net_usage_words = net_usage_words; r.status = status;returnr; }
上面的逻辑很大程度上和implicit为true时的逻辑重复，估计以后会重构。
接下来值得注意的是这里：
if( read_mode != db_read_mode::SPECULATIVE && pending->_block_status == controller::block_status::incomplete ) {//this may happen automatically in destructor, but I prefere make it more explicittrx_context.undo(); }else{ restore.cancel(); trx_context.squash(); }
TODO trx_context.undo
这里调用database::session对应的函数，
!> Eosforce不同之处
以上是EOS的流程，这里我们再来看看Eosforce的不同之处，Eosforce与EOS一个明显的不同是Eosforce采用了基于手续费的资源模型， 这种模型意味着，如果一个交易在超级节点打包进块时失败了，此时也要收取手续费，否则会造成潜在的攻击风险，所以Eosforce中，执行失败的交易也会写入区块中，这样每次执行时会调用对应onfee。 另一方面, Eosforce虽然使用手续费，但是还是区分cpu，net，ram资源，并且在大的限制上依然进行检查。 后续Eosforce会完成新的资源模型，这里会有所改动。
Eosforce中的push_transaction函数如下：
transaction_trace_ptrpush_transaction(consttransaction_metadata_ptr& trx, fc::time_point deadline,uint32_tbilled_cpu_time_us,boolexplicit_billed_cpu_time =false){ EOS_ASSERT(deadline != fc::time_point(), transaction_exception,"deadline cannot be uninitialized");// eosforce暂时没有开放延迟交易和上下文无关交易EOS_ASSERT(trx->trx.delay_sec.value ==0UL, transaction_exception,"delay,transaction failed"); EOS_ASSERT(trx->trx.context_free_actions.size()==0, transaction_exception,"context free actions size should be zero!");// 在eosforce中，为了安全性，对于特定一些交易进行了额外的验证，主要是考虑到，系统会将执行错误的交易写入区块// 此时就要先验证下交易内容，特别是大小上有没有超出限制，否则将会带来安全问题。check_action(trx->trx.actions); transaction_trace_ptr trace;try{// 一样的代码 略去...try{// 一样的代码 略去...// 处理手续费EOS_ASSERT(trx->trx.fee == txfee.get_required_fee(trx->trx), transaction_exception,"set tx fee failed"); EOS_ASSERT(txfee.check_transaction(trx->trx) ==true, transaction_exception,"transaction include actor more than one");try{// 这里会执行onfee合约，也是通过`push_transaction`实现的autoonftrx =std::make_shared( get_on_fee_transaction(trx->trx.fee, trx->trx.actions[0].authorization[0].actor) ); onftrx->implicit =true;autoonftrace = push_transaction( onftrx, fc::time_point::maximum(), config::default_min_transaction_cpu_usage,true);// 这里如果执行失败直接抛出异常，不会执行下面的东西if( onftrace->except )throw*onftrace->except; }catch(constfc::exception &e) { EOS_ASSERT(false, transaction_exception,"on fee transaction failed, exception: ${e}", ("e", e)); }catch( ... ) { EOS_ASSERT(false, transaction_exception,"on fee transaction failed, but shouldn't enough asset to pay for transaction fee"); } }// 注意这一层try catch，因为eos中出错的交易会被抛弃，所以eos的异常会被直接抛出到外层// 而在eosforce中出错的交易会进入区块// 但是要注意，这里如果这里并不是在超级节点出块时调用，虽然也会执行下面的逻辑，但是不会被转发给超级节点。try{if(explicit_billed_cpu_time && billed_cpu_time_us ==0){// 在eosforce中 因为超级节点打包区块时失败的交易也会被写入区块中，// 而很多交易失败的原因不是交易本身有问题，而是在执行交易时，资源上限被触发，导致交易被直接判定为失败，// 这时写入区块的交易的cpu消耗是0, 这里是需要失败的，否则重跑区块时会出现不同步的情况EOS_ASSERT(false, transaction_exception,"billed_cpu_time_us is 0"); } trx_context.exec(); trx_context.finalize();// Automatically rounds up network and CPU usage in trace and bills payers if successful}catch(constfc::exception &e) { trace->except = e; trace->except_ptr =std::current_exception();// eosforce加了一些日志if(head->block_num !=1) { elog("---trnasction exe failed--------trace: ${trace}", ("trace", trace)); } }autorestore = make_block_restore_point();if(!trx->implicit) {// 这里不太好的地方是，对于出错的交易也被标为`executed`（严格说也确实是executed），后续eosforce将会重构这里transaction_receipt::status_enum s = (trx_context.delay == fc::seconds(0)) ? transaction_receipt::executed : transaction_receipt::delayed; trace->receipt = push_receipt(trx->packed_trx, s, trx_context.billed_cpu_time_us, trace->net_usage); pending->_pending_block_state->trxs.emplace_back(trx); }else{ transaction_receipt_header r; r.status = transaction_receipt::executed; r.cpu_usage_us = trx_context.billed_cpu_time_us; r.net_usage_words = trace->net_usage /8; trace->receipt = r; }// 以下是相同的} FC_CAPTURE_AND_RETHROW((trace)) }/// push_transaction
可以看出主要不同就是手续费导致的，这里必须要注意，就是eosforce中区块内会包括一些出错的交易。
4. apply_context代码分析
这里我们来看看action的执行过程，上面在dispatch_action中创建apply_context执行action，我们这里分析这一块的代码。
apply_context结构比较大，主要是数据结构实现内容很多，这里我们只分析功能点，从这方面入手看结构，先从exec开始， 在上面push_trx最终调用的就是这个函数，执行actions：
voidapply_context::exec(){// 先添加receiver，关于_notified下面分析_notified.push_back(receiver);// 执行exec_one，这里是实际执行action的地方，下面单独分析trace = exec_one();// 下面处理inline action// 注意不是从0开始，会绕过上面添加的receiverfor(uint32_ti =1; i < _notified.size(); ++i ) { receiver = _notified[i];// 通知指定的账户 关于_notified下面分析trace.inline_traces.emplace_back( exec_one() ); }// 防止调用inline action过深if( _cfa_inline_actions.size() >0|| _inline_actions.size() >0) { EOS_ASSERT( recurse_depth < control.get_global_properties().configuration.max_inline_action_depth, transaction_exception,"inline action recursion depth reached"); }// 先执行_cfa_inline_actionsfor(constauto& inline_action : _cfa_inline_actions ) { trace.inline_traces.emplace_back(); trx_context.dispatch_action( trace.inline_traces.back(), inline_action, inline_action.account,true, recurse_depth +1); }// 再执行_inline_actionsfor(constauto& inline_action : _inline_actions ) { trace.inline_traces.emplace_back(); trx_context.dispatch_action( trace.inline_traces.back(), inline_action, inline_action.account,false, recurse_depth +1); }}/// exec()
这里的逻辑基本都是处理inline action，inline action允许在一个合约中触发另外一个合约的调用，需要注意的是这里与编程语言中的函数调用并不相同，从上面代码也可以看出，系统会先执行合约对应的action，再执行合约中的声明调用的inline action，注意recurse_depth，显然循环调用合约次数深度过高会引起错误。
为了更好的理解代码过程我们先来仔细看下 inline action。在合约中可以这样使用，代码出自dice：
//@abi actionvoiddeposit(constaccount_name from,constasset& quantity ){ ... action( permission_level{ from, N(active) }, N(eosio.token), N(transfer),std::make_tuple(from, _self, quantity,std::string("")) ).send(); ... }
这里send会把action打包并调用下面的send_inline：
voidsend_inline( array_ptr data,size_tdata_len ){//TODO:Why is this limit even needed? And why is it not consistently checked on actions in input or deferred transactionsEOS_ASSERT( data_len < context.control.get_global_properties().configuration.max_inline_action_size, inline_action_too_big,"inline action too big"); action act; fc::raw::unpack(data, data_len, act); context.execute_inline(std::move(act)); }
可以看到这里调用的是内部的execute_inline函数：
/**
* This will execute an action after checking the authorization. Inline transactions are
* implicitly authorized by the current receiver (running code). This method has significant
* security considerations and several options have been considered:
*
* 1. priviledged accounts (those marked as such by block producers) can authorize any action
* 2. all other actions are only authorized by 'receiver' which means the following:
* a. the user must set permissions on their account to allow the 'receiver' to act on their behalf
*
* Discarded Implemenation: at one point we allowed any account that authorized the current transaction
* to implicitly authorize an inline transaction. This approach would allow privelege escalation and
* make it unsafe for users to interact with certain contracts. We opted instead to have applications
* ask the user for permission to take certain actions rather than making it implicit. This way users
* can better understand the security risk.
*/voidapply_context::execute_inline( action&& a ) {// 先做了一些检查auto* code = control.db().find(a.account); EOS_ASSERT( code !=nullptr, action_validate_exception,"inline action's code account ${account} does not exist", ("account", a.account) );for(constauto& auth : a.authorization ) {auto* actor = control.db().find(auth.actor); EOS_ASSERT( actor !=nullptr, action_validate_exception,"inline action's authorizing actor ${account} does not exist", ("account", auth.actor) ); EOS_ASSERT( control.get_authorization_manager().find_permission(auth) !=nullptr, action_validate_exception,"inline action's authorizations include a non-existent permission: ${permission}", ("permission", auth) ); }// No need to check authorization if: replaying irreversible blocks; contract is privileged; or, contract is calling itself.// 上面几种情况下不需要做权限检查if( !control.skip_auth_check() && !privileged && a.account != receiver ) { control.get_authorization_manager() .check_authorization( {a}, {}, {{receiver, config::eosio_code_name}}, control.pending_block_time() - trx_context.published,std::bind(&transaction_context::checktime, &this->trx_context),false);//QUESTION: Is it smart to allow a deferred transaction that has been delayed for some time to get away// with sending an inline action that requires a delay even though the decision to send that inline// action was made at the moment the deferred transaction was executed with potentially no forewarning?}// 这里只是把这个act放入_inline_actions列表中，并没有执行。_inline_actions.emplace_back( move(a) );}
注意上面代码中最后的_inline_actions，这里面放着执行action时所触发的所有action的数据，回到exec中：
// 防止调用inline action过深if( _cfa_inline_actions.size() >0|| _inline_actions.size() >0) { EOS_ASSERT( recurse_depth < control.get_global_properties().configuration.max_inline_action_depth, transaction_exception,"inline action recursion depth reached"); }// 先执行_cfa_inline_actionsfor(constauto& inline_action : _cfa_inline_actions ) { trace.inline_traces.emplace_back(); trx_context.dispatch_action( trace.inline_traces.back(), inline_action, inline_action.account,true, recurse_depth +1); }// 再执行_inline_actionsfor(constauto& inline_action : _inline_actions ) { trace.inline_traces.emplace_back(); trx_context.dispatch_action( trace.inline_traces.back(), inline_action, inline_action.account,false, recurse_depth +1); }
这后半部分就是执行action，注意上面我们没有跟踪_cfa_inline_actions的流程，这里和_inline_actions的流程是一致的，区别是在合约中由send_context_free触发。
以上我们看了下inline action的处理，上面exec中没有提及的是_notified，下面来看看这个， 在合约中可以调用require_recipient：
// 把账户添加至通知账户列表中voidapply_context::require_recipient( account_name recipient ) {if( !has_recipient(recipient) ) { _notified.push_back(recipient); }}
在执行完action之后，执行inline action之前（严格上说inline action 不是action的一部分，所以在这之前）会通知所有在执行合约过程中添加入_notified的账户：
// 注意不是从0开始，会绕过上面添加的receiverfor(uint32_ti =1; i < _notified.size(); ++i ) { receiver = _notified[i]; trace.inline_traces.emplace_back( exec_one() ); }
这里可能有疑问的是为什么又执行了一次exec_one，下面分析exec_one时会说明。
以上我们分析了一下exec，这里主要是调用exec_one来执行合约，下面就来看看exec_one：
// 执行action，注意`receiver`action_trace apply_context::exec_one(){autostart = fc::time_point::now();constauto& cfg = control.get_global_properties().configuration;try{// 这里是receiver是作为一个合约账户的情况constauto& a = control.get_account( receiver ); privileged = a.privileged;// 这里检查action是不是系统内部的合约，关于这方面下面会单独分析autonative = control.find_apply_handler( receiver, act.account, act.name );if( native ) {if( trx_context.can_subjectively_fail && control.is_producing_block()) { control.check_contract_list( receiver ); control.check_action_list( act.account, act.name ); }// 这里会执行cpp中定义的代码(*native)( *this); }// 如果是合约账户的话，这里会执行if( a.code.size() >0// 这里对 setcode 单独处理了一下，这是因为setcode和其他合约都使用了code数据// 但是 setcode 是在cpp层调用的，code作为参数，所以这里就不会调用code。&& !(act.account == config::system_account_name && act.name == N( setcode ) && receiver == config::system_account_name)) {if( trx_context.can_subjectively_fail && control.is_producing_block()) {// 各种黑白名单检查control.check_contract_list( receiver );// 这里主要是account黑白名单，不再细细说明control.check_action_list( act.account, act.name );// 这里主要是action黑名单，不再细细说明}try{// 这里就会调用虚拟机执行code，关于这方面，我们会单独写一篇分析文档control.get_wasm_interface().apply( a.code_version, a.code, *this); }catch(constwasm_exit& ) {} } } FC_RETHROW_EXCEPTIONS(warn,"pending console output: ${console}", ("console", _pending_console_output.str()))// 这里的代码分成了两部分，这里其实应该重构一下，下面的逻辑应该单独提出一个函数。// 上面对于`_notified`其实就是从这里开始// 整理action_receipt数据action_receipt r; r.receiver = receiver; r.act_digest = digest_type::hash(act); r.global_sequence = next_global_sequence(); r.recv_sequence = next_recv_sequence( receiver );constauto& account_sequence = db.get(act.account); r.code_sequence = account_sequence.code_sequence; r.abi_sequence = account_sequence.abi_sequence;for(constauto& auth : act.authorization ) { r.auth_sequence[auth.actor] = next_auth_sequence( auth.actor ); }// 这里会生成一个action_trace结构直接用来标志action_tracet(r); t.trx_id = trx_context.id; t.act = act; t.console = _pending_console_output.str();// 放入以执行的列表中trx_context.executed.emplace_back( move(r) );// 日志if( control.contracts_console() ) { print_debug(receiver, t); } reset_console(); t.elapsed = fc::time_point::now() - start;returnt;}
这里先看看对于加入_notified的账户的处理， 正常的逻辑中，执行的结果中会产生所有_notified（不包含最初的receiver）中账户对应的action_trace的列表， 这些会存入inline_traces中，这里其实是把通知账户的过程也当作了一种“inline action”。
这些trace信息会被其他插件利用，目前主要是history插件中的on_action_trace函数，这里会将所有action的执行信息和结果存入action_history_object供api调用，具体的过程这里不再消息描述。
以上就是整个apply_context执行合约的过程。
5. 几个内置的action
在EOS中有一些action的实现是在cpp层的，这里单独看下。
如果看合约中，会有这样几个只有定义而没有实现的合约：
/*
* Method parameters commented out to prevent generation of code that parses input data.
*/classnative:publiceosio::contract {public:usingeosio::contract::contract;/**
* Called after a new account is created. This code enforces resource-limits rules
* for new accounts as well as new account naming conventions.
*
* 1. accounts cannot contain '.' symbols which forces all acccounts to be 12
* characters long without '.' until a future account auction process is implemented
* which prevents name squatting.
*
* 2. new accounts must stake a minimal number of tokens (as set in system parameters)
* therefore, this method will execute an inline buyram from receiver for newacnt in
* an amount equal to the current new account creation fee.
*/voidnewaccount( account_name creator, account_name newact/* no need to parse authorites
const authority& owner,
const authority& active*/);voidupdateauth(/*account_name account,
permission_name permission,
permission_name parent,
const authority& data*/){}voiddeleteauth(/*account_name account, permission_name permission*/){}voidlinkauth(/*account_name account,
account_name code,
action_name type,
permission_name requirement*/){}voidunlinkauth(/*account_name account,
account_name code,
action_name type*/){}voidcanceldelay(/*permission_level canceling_auth, transaction_id_type trx_id*/){}voidonerror(/*const bytes&*/){} };
这些合约是在eos项目的cpp中实现的，这里的声明是为了适配合约名相关的api， 这里Eosforce有个问题，就是在最初的实现中，将这些声明删去了，导致json_to_bin api出错，这里后续会修正这个问题。
对于这些合约，在上面我们指出是在exec_one中处理的，实际的注册在这里：
voidset_apply_handler( account_name receiver, account_name contract, action_name action, apply_handler v ){ apply_handlers[receiver][make_pair(contract,action)] = v; } ...#defineSET_APP_HANDLER( receiver, contract, action) \ set_apply_handler( #receiver, #contract, #action, &BOOST_PP_CAT(apply_, BOOST_PP_CAT(contract, BOOST_PP_CAT(_,action) ) ) )SET_APP_HANDLER( eosio, eosio, newaccount ); SET_APP_HANDLER( eosio, eosio, setcode ); SET_APP_HANDLER( eosio, eosio, setabi ); SET_APP_HANDLER( eosio, eosio, updateauth ); SET_APP_HANDLER( eosio, eosio, deleteauth ); SET_APP_HANDLER( eosio, eosio, linkauth ); SET_APP_HANDLER( eosio, eosio, unlinkauth );/*
SET_APP_HANDLER( eosio, eosio, postrecovery );
SET_APP_HANDLER( eosio, eosio, passrecovery );
SET_APP_HANDLER( eosio, eosio, vetorecovery );
*/SET_APP_HANDLER( eosio, eosio, canceldelay );
!> Eosforce不同 ： 在eosforce中有些合约被屏蔽了。
这里不好查找的一点是，在宏定义中拼接了函数名，所以实际对应的是apply_eosio_×的函数，如newaccount对应的是apply_eosio_newaccount。
我们这里专门分析下apply_eosio_newaccount，apply_eosio_setcode和apply_eosio_setabi，后续会有文档专门分析所有系统合约。
5.1 apply_eosio_newaccount
新建用户没有什么特别之处，这里的写法和合约中类似：
voidapply_eosio_newaccount(apply_context& context){// 获得数据autocreate = context.act.data_as();try{// 各种检查context.require_authorization(create.creator);// context.require_write_lock( config::eosio_auth_scope );auto& authorization = context.control.get_mutable_authorization_manager(); EOS_ASSERT( validate(create.owner), action_validate_exception,"Invalid owner authority"); EOS_ASSERT( validate(create.active), action_validate_exception,"Invalid active authority");auto& db = context.db;autoname_str = name(create.name).to_string(); EOS_ASSERT( !create.name.empty(), action_validate_exception,"account name cannot be empty"); EOS_ASSERT( name_str.size() <=12, action_validate_exception,"account names can only be 12 chars long");// Check if the creator is privilegedconstauto&creator = db.get(create.creator);if( !creator.privileged ) {// EOS中eosio.的账户都是系统账户，Eosforce中没有指定保留账户EOS_ASSERT( name_str.find("eosio.") !=0, action_validate_exception,"only privileged accounts can have names that start with 'eosio.'"); }// 检查账户重名autoexisting_account = db.find(create.name); EOS_ASSERT(existing_account ==nullptr, account_name_exists_exception,"Cannot create account named ${name}, as that name is already taken", ("name", create.name));// 创建账户constauto& new_account = db.create([&](auto& a) { a.name = create.name; a.creation_date = context.control.pending_block_time(); }); db.create([&](auto& a) { a.name = create.name; });for(constauto& auth : { create.owner, create.active } ){ validate_authority_precondition( context, auth ); }constauto& owner_permission = authorization.create_permission( create.name, config::owner_name,0,std::move(create.owner) );constauto& active_permission = authorization.create_permission( create.name, config::active_name, owner_permission.id,std::move(create.active) );// 初始化账户资源context.control.get_mutable_resource_limits_manager().initialize_account(create.name);int64_tram_delta = config::overhead_per_account_ram_bytes; ram_delta +=2*config::billable_size_v; ram_delta += owner_permission.auth.get_billable_size(); ram_delta += active_permission.auth.get_billable_size(); context.trx_context.add_ram_usage(create.name, ram_delta);} FC_CAPTURE_AND_RETHROW( (create) ) }
5.2 apply_eosio_setcode和apply_eosio_setabi
apply_eosio_setcode和apply_eosio_setabi用来提交合约，实现上也没有特别之处， 唯一注意的是之前谈过，apply_eosio_setcode既是系统合约，又带code，这里的code作为参数
voidapply_eosio_setcode(apply_context& context){constauto& cfg = context.control.get_global_properties().configuration;// 获取数据auto& db = context.db;autoact = context.act.data_as();// 权限context.require_authorization(act.account); EOS_ASSERT( act.vmtype ==0, invalid_contract_vm_type,"code should be 0"); EOS_ASSERT( act.vmversion ==0, invalid_contract_vm_version,"version should be 0"); fc::sha256 code_id;/// default ID == 0if( act.code.size() >0) { code_id = fc::sha256::hash( act.code.data(), (uint32_t)act.code.size() ); wasm_interface::validate(context.control, act.code); }constauto& account = db.get(act.account);int64_tcode_size = (int64_t)act.code.size();int64_told_size = (int64_t)account.code.size() * config::setcode_ram_bytes_multiplier;int64_tnew_size = code_size * config::setcode_ram_bytes_multiplier; EOS_ASSERT( account.code_version != code_id, set_exact_code,"contract is already running this version of code"); db.modify( account, [&](auto& a ) {/**TODO:consider whether a microsecond level local timestamp is sufficient to detect code version changes*///TODO:update setcode message to include the hash, then validate it in validatea.last_code_update = context.control.pending_block_time(); a.code_version = code_id; a.code.resize( code_size );if( code_size >0)memcpy( a.code.data(), act.code.data(), code_size ); });constauto& account_sequence = db.get(act.account); db.modify( account_sequence, [&](auto& aso ) { aso.code_sequence +=1; });// 更新资源消耗if(new_size != old_size) { context.trx_context.add_ram_usage( act.account, new_size - old_size ); }}voidapply_eosio_setabi(apply_context& context){auto& db = context.db;autoact = context.act.data_as(); context.require_authorization(act.account);constauto& account = db.get(act.account);int64_tabi_size = act.abi.size();int64_told_size = (int64_t)account.abi.size();int64_tnew_size = abi_size; db.modify( account, [&](auto& a ) { a.abi.resize( abi_size );if( abi_size >0)memcpy( a.abi.data(), act.abi.data(), abi_size ); });constauto& account_sequence = db.get(act.account); db.modify( account_sequence, [&](auto& aso ) { aso.abi_sequence +=1; });// 更新资源消耗if(new_size != old_size) { context.trx_context.add_ram_usage( act.account, new_size - old_size ); }}
6. 需要留意的问题
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