跟原力一起玩转EOS源码-Push Transaction机制

EOS源码备忘-Push Transaction机制

这里我们讨论EOS Push Transaction 的逻辑，这块EOS与Eosforce实现有一些区别，我们会着重点出。 关于wasm相关的内容我们会有一片专门的文档分析。

我们这里通常将Transaction译做交易，其实这里应该是事务的意思。

1. Transaction与Action
   在EOS中Transaction与Action是最重要的几个类型， 在EOS中，所有的链上行为都是Action，Transaction是一系列Action组成的事务。

EOS中使用继承体系划分trx与action结构，关系图如下：

transaction_header <- transaction <- signed_transaction <- deferred_transaction

                    |

            packed_transaction

1.1 Action

我们这里先看一下Action的声明：

// 权限结构structpermission_level{account_name actor; permission_name permission; }; …structaction{account_name account; action_name name;// 执行所需的权限vector authorization; bytes data; …// 打包成二进制templateTdata_as()const{ … } };

Action没有什么特别的内容，但要注意：

!> 在EOS中一个transaction中包含很多个action，而在Eosforce中一个trx只能包括一个action。

1.2 Transaction

下面我们分析一下transaction，这里简写为trx。

首先看下

/**

*  The transaction header contains the fixed-sized data

*  associated with each transaction. It is separated from

*  the transaction body to facilitate partial parsing of

*  transactions without requiring dynamic memory allocation.

*

*  All transactions have an expiration time after which they

*  may no longer be included in the blockchain. Once a block

*  with a block_header::timestamp greater than expiration is

*  deemed irreversible, then a user can safely trust the transaction

*  will never be included.

*

*  Each region is an independent blockchain, it is included as routing

*  information for inter-blockchain communication. A contract in this

*  region might generate or authorize a transaction intended for a foreign

*  region.

*/structtransaction_header{time_point_sec        expiration;///< trx超时时间uint16_tref_block_num      =0U;// 包含trx的block num 注意这个值是后2^16个块中uint32_tref_block_prefix    =0UL;// blockid的低32位fc::unsigned_int      max_net_usage_words =0UL;// 网络资源上限uint8_tmax_cpu_usage_ms    =0;// cpu资源上限fc::unsigned_int      delay_sec          =0UL;/// 延迟交易的延迟时间/**

  * @return the absolute block number given the relative ref_block_num

  * 计算ref_block_num

  */block_num_typeget_ref_blocknum( block_num_type head_blocknum )const{return((head_blocknum/0xffff)*0xffff) + head_blocknum%0xffff;      }voidset_reference_block(constblock_id_type& reference_block );boolverify_reference_block(constblock_id_type& reference_block )const;voidvalidate()const;  };

transaction_header包含一个trx中固定长度的数据，这里之所以要单独提出来主要是为了优化。

transaction视为交易体数据，这里主要是存储这个trx包含的action。

/**

*  A transaction consits of a set of messages which must all be applied or

*  all are rejected. These messages have access to data within the given

*  read and write scopes.

*/

// 在EOS中一个交易中 action要么全部执行，要么都不执行

struct transaction : public transaction_header {

  vector        context_free_actions;

  vector        actions;

  extensions_type        transaction_extensions;

  // 获取trx id

  transaction_id_type        id()const;

  digest_type                sig_digest( const chain_id_type& chain_id, const vector& cfd = vector() )const;

...

};

注意这里的context_free_actions，这里指上下文无关的Action，具体信息可以参见这里： https://medium.com/@bytemaster/eosio-development-update-272198df22c1 和 https://github.com/EOSIO/eos/issues/1387。 如果一个Action执行时只依赖与transaction的数据，而不依赖与链上的状态，这样的action可以并发的执行。

另外一个值得注意的是trx id：

transaction_id_type transaction::id()const{ digest_type::encoder enc; fc::raw::pack( enc, *this);returnenc.result();}

!> Eosforce不同

在Eosforce中为了添加手续费信息，trx与EOS结构不同，主要是增加了fee， 在transaction中：

struct transaction : public transaction_header {

  vector        context_free_actions;

  vector        actions;

  extensions_type        transaction_extensions;

  asset                  fee; // EOSForce 增加的手续费，在客户端push trx时需要写入

  transaction_id_type        id()const;

  digest_type                sig_digest( const chain_id_type& chain_id, const vector& cfd = vector() )const;

  flat_set  get_signature_keys( const vector& signatures,

                                                const chain_id_type& chain_id,

                                                const vector& cfd = vector(),

                                                bool allow_duplicate_keys = false,

                                                bool use_cache = true )const;

  uint32_t total_actions()const { return context_free_actions.size() + actions.size(); }

  account_name first_authorizor()const {

    for( const auto& a : actions ) {

        for( const auto& u : a.authorization )

          return u.actor;

    }

    return account_name();

  }

};

在 https://eosforce.github.io/Documentation/#/zh-cn/eosforce_client_develop_guild 这篇文档里也有说明。

这里计算trx id时完全使用trx的数据，这意味着，如果是两个trx数据完全一致，特别的他们在一个区块中，那么这两个trx的id就会是一样的。

1.3 signed_transaction

一个trx签名之后会得到一个signed_transaction，

structsigned_transaction:publictransaction { …vector signatures;// 签名vector context_free_data;// 上下文无关的action所使用的数据// 签名constsignature_type&sign(constprivate_key_type& key,constchain_id_type& chain_id);signature_typesign(constprivate_key_type& key,constchain_id_type& chain_id)const; flat_set get_signature_keys(constchain_id_type& chain_id,boolallow_duplicate_keys =false,booluse_cache =true)const; };

signed_transaction包含签名数据和上下文无关的action所使用的数据，

这里要谈一下context_free_data，可以参见 https://github.com/EOSIO/eos/commit/a41b4d56b5cbfd0346de34b0e03819f72e834041 ，之前我们看过context_free_actions， 在上下文无关的action中可以去从context_free_data获取数据，可以参见在api_tests.cpp中的测试用例：

… {// back to normal actionactionact1(pl, da); signed_transaction trx; trx.context_free_actions.push_back(act); trx.context_free_data.emplace_back(fc::raw::pack(100));// verify payload matches context free datatrx.context_free_data.emplace_back(fc::raw::pack(200)); trx.actions.push_back(act1);// attempt to access non context free apifor(uint32_ti =200; i <=211; ++i) { trx.context_free_actions.clear(); trx.context_free_data.clear(); cfa.payload = i; cfa.cfd_idx =1;actioncfa_act({}, cfa); trx.context_free_actions.emplace_back(cfa_act); trx.signatures.clear(); set_transaction_headers(trx); sigs = trx.sign(get_private_key(N(testapi),“active”), control->get_chain_id()); BOOST_CHECK_EXCEPTION(push_transaction(trx), unaccessible_api, [](constfc::exception& e) {returnexpect_assert_message(e,“only context free api’s can be used in this context”); } ); }…

这里可以作为context_free_action的一个例子，在test_api.cpp中的合约会调用void test_action::test_cf_action()函数：

// 这个是测试context_free_action的action

void test_action::test_cf_action() {

eosio::action act = eosio::get_action( 0, 0 );

cf_action cfa = act.data_as();

if ( cfa.payload == 100 ) {

  // verify read of get_context_free_data, also verifies system api access

  // 测试在合约中通过 get_context_free_data 获取 context_free_data

  int size = get_context_free_data( cfa.cfd_idx, nullptr, 0 );

  eosio_assert( size > 0, "size determination failed" );

  eosio::bytes cfd( static_cast(size) );

  size = get_context_free_data( cfa.cfd_idx, &cfd[0], static_cast(size) );

  eosio_assert(static_cast(size) == cfd.size(), "get_context_free_data failed" );

  uint32_t v = eosio::unpack( &cfd[0], cfd.size() );

  eosio_assert( v == cfa.payload, "invalid value" );

  // 以下是测试一些功能

  // verify crypto api access

  checksum256 hash;

  char test[] = "test";

  ...

  // verify context_free_system_api

  eosio_assert( true, "verify eosio_assert can be called" );

  // 下面是测试一些在上下文无关action中不能使用的功能

} else if ( cfa.payload == 200 ) {

  // attempt to access non context free api, privileged_api

  is_privileged(act.name);

  eosio_assert( false, "privileged_api should not be allowed" );

} else if ( cfa.payload == 201 ) {

  // attempt to access non context free api, producer_api

  get_active_producers( nullptr, 0 );

  eosio_assert( false, "producer_api should not be allowed" );



...

} else if ( cfa.payload == 211 ) {

  send_deferred( N(testapi), N(testapi), "hello", 6 );

  eosio_assert( false, "transaction_api should not be allowed" );

}

}

接下来我们来看一看packed_transaction，通过这个类我们可以将trx打包，这样可以最大的节省空间，关于它的功能，会在下面使用的提到。

2. Transaction的接收和转发流程
   了解Transaction类定义之后，我们先来看一下trx在EOS系统中的接收和转发流程，确定发起trx的入口， 在EOS中，大部分trx都是由用户所操纵的客户端发向同步节点，再通过同步网络发送给超级节点，超级节点会把trx打包进块，这里我们梳理一下这里的逻辑，

首先，关于客户端提交trx的流程，可以参见 https://eosforce.github.io/Documentation/#/zh-cn/eosforce_client_develop_guild ， 我们这里从node的角度看是怎么处理收到的trx的。

对于一个节点，trx可能是其他节点同步过来的，也可能是客户端通过api请求的，我们先看看api：

EOS中通过http_plugin插件响应http请求，这里我们只看处理逻辑，在chain_api_plugin.cpp中注册的这两个：

voidchain_api_plugin::plugin_startup() { ilog(“starting chain_api_plugin”); my.reset(newchain_api_plugin_impl(app().get_plugin().chain()));autoro_api = app().get_plugin().get_read_only_api();autorw_api = app().get_plugin().get_read_write_api(); app().get_plugin().add_api({ … CHAIN_RW_CALL_ASYNC(push_transaction, chain_apis::read_write::push_transaction_results,202), CHAIN_RW_CALL_ASYNC(push_transactions, chain_apis::read_write::push_transactions_results,202) });}

最终实际调用的是这里：

// 调用流程 push_transactions -> push_recurse -> push_transactionvoidread_write::push_transaction(constread_write::push_transaction_params& params, next_function next) {try{autopretty_input =std::make_shared();autoresolver = make_resolver(this, abi_serializer_max_time);try{// 这里在使用 packed_transaction 解包abi_serializer::from_variant(params, *pretty_input, resolver, abi_serializer_max_time); } EOS_RETHROW_EXCEPTIONS(chain::packed_transaction_type_exception,“Invalid packed transaction”)// 这里调用 incoming::methods::transaction_async 函数app().get_method()(pretty_input,true, [this, next](constfc::static_variant& result) ->void{ …// 返回返回值， 略去}); }catch( boost::interprocess::bad_alloc& ) { raise(SIGUSR1); } CATCH_AND_CALL(next);}

注意这里的 persist_until_expired 参数，我们在 EOS源码备忘-Block Produce机制 这篇文档中分析过。 incoming::methods::transaction_async注册的是on_incoming_transaction_async函数：

my->_incoming_transaction_async_provider = app().get_method().register_provider([this](constpacked_transaction_ptr& trx,boolpersist_until_expired, next_function next) ->void{returnmy->on_incoming_transaction_async(trx, persist_until_expired, next ); });

on_incoming_transaction_async如下：

voidon_incoming_transaction_async(constpacked_transaction_ptr& trx,boolpersist_until_expired, next_function next){ chain::controller& chain = app().get_plugin().chain();if(!chain.pending_block_state()) { _pending_incoming_transactions.emplace_back(trx, persist_until_expired, next);return; }autoblock_time = chain.pending_block_state()->header.timestamp.to_time_point();// 返回结果的回调autosend_response = [this, &trx, &next](constfc::static_variant& response) { next(response);if(response.contains()) { _transaction_ack_channel.publish(std::pair(response.get(), trx)); }else{ _transaction_ack_channel.publish(std::pair(nullptr, trx)); } };autoid = trx->id();// 超时时间检查if( fc::time_point(trx->expiration()) < block_time ) { send_response(std::static_pointer_cast(std::make_shared(FC_LOG_MESSAGE(error,“expired transaction ${id}”, (“id”, id)) )));return; }// 检查是否是已处理过的trxif( chain.is_known_unexpired_transaction(id) ) { send_response(std::static_pointer_cast(std::make_shared(FC_LOG_MESSAGE(error,“duplicate transaction ${id}”, (“id”, id)) )));return; }// 看看是否超过最大的执行时间了autodeadline = fc::time_point::now() + fc::milliseconds(_max_transaction_time_ms);booldeadline_is_subjective =false;if(_max_transaction_time_ms <0|| (_pending_block_mode == pending_block_mode::producing && block_time < deadline) ) { deadline_is_subjective =true; deadline = block_time; }try{// 这里直接调用push_transaction来执行trxautotrace = chain.push_transaction(std::make_shared(*trx), deadline);if(trace->except) {if(failure_is_subjective(*trace->except, deadline_is_subjective)) { _pending_incoming_transactions.emplace_back(trx, persist_until_expired, next); }else{autoe_ptr = trace->except->dynamic_copy_exception(); send_response(e_ptr); } }else{if(persist_until_expired) {// if this trx didnt fail/soft-fail and the persist flag is set, store its ID so that we can// ensure its applied to all future speculative blocks as well._persistent_transactions.insert(transaction_id_with_expiry{trx->id(), trx->expiration()}); } send_response(trace); } }catch(constguard_exception& e ) { app().get_plugin().handle_guard_exception(e); }catch( boost::interprocess::bad_alloc& ) { raise(SIGUSR1); } CATCH_AND_CALL(send_response); }

注意上面的is_known_unexpired_transaction，代码如下：

boolcontroller::is_known_unexpired_transaction(consttransaction_id_type& id)const{returndb().find(id);}

与之对应的是这个函数：

voidtransaction_context::record_transaction(consttransaction_id_type& id, fc::time_point_sec expire ) {try{ control.db().create([&](transaction_object& transaction) { transaction.trx_id = id; transaction.expiration = expire; }); }catch(constboost::interprocess::bad_alloc& ) {throw; }catch( … ) { EOS_ASSERT(false, tx_duplicate,“duplicate transaction ${id}”, (“id”, id ) ); } }/// record_transaction

在push_transaction中会调用到，记录trx已经被处理过了。

下面我们来看看send_response这个回调：

autosend_response = [this, &trx, &next](constfc::static_variant& response) { next(response);if(response.contains()) { _transaction_ack_channel.publish(std::pair(response.get(), trx)); }else{ _transaction_ack_channel.publish(std::pair(nullptr, trx)); } };

在执行之后会调用send_response，这里是将结果发送到_transaction_ack_channel中，对于_transaction_ack_channel， 这个实际对应的是下面这个类型：

namespacecompat {namespacechannels {usingtransaction_ack = channel_decl>; } }

在EOS中在net_plugin注册响应这个channel的函数:

  my->incoming_transaction_ack_subscription =

        app().get_channel().subscribe(

              boost::bind(&net_plugin_impl::transaction_ack, my.get(), _1));

处理的函数如下：

voidnet_plugin_impl::transaction_ack(conststd::pair& results) { transaction_id_type id = results.second->id();if(results.first) { fc_ilog(logger,“signaled NACK, trx-id = ${id} : ${why}”,(“id”, id)(“why”, results.first->to_detail_string())); dispatcher->rejected_transaction(id); }else{ fc_ilog(logger,“signaled ACK, trx-id = ${id}”,(“id”, id)); dispatcher->bcast_transaction(*results.second); } }

这里会将运行正常的广播给其他节点，这其中会发送给超级节点打包入块，打包过程可以参见 https://eosforce.github.io/Documentation/#/zh-cn/code/block_produce 。

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>>  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(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(trx) );

    signed_id = digest_type::hash(packed_trx);

  }

  const flat_set& 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;

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receiveraction_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®; 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® );// 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