【刘文彬】区块链 + 大数据：EOS存储

    action_mroot是始终有值的，哪怕transaction_mroot是0，这是因为出块本身也是一个action动作onblock，这个动作调用的是system合约的onblock函数。TODO：源码分析

/**
*  At the start of each block we notify the system contract with a transaction that passes in
*  the block header of the prior block (which is currently our head block)
*/
signed_transaction get_on_block_transaction()
{
  action on_block_act;
  on_block_act.account = config::system_account_name;
  on_block_act.name = N(onblock);
  on_block_act.authorization = vector<permission_level>{{config::system_account_name, config::active_name}};
  on_block_act.data = fc::raw::pack(self.head_block_header());

  signed_transaction trx;
  trx.actions.emplace_back(std::move(on_block_act));
  trx.set_reference_block(self.head_block_id());
  trx.expiration = self.pending_block_time() + fc::microseconds(999'999); // Round up to nearest second to avoid appearing expired
  return trx;
}

evsward@evsward-TM1701:~/work/src/github.com/eos/tutorials/bios-boot-tutorial$ cleos --wallet-url http://127.0.0.1:6666 --url http://127.0.0.1:8000 get block 440
{
  "timestamp": "2018-08-14T08:47:09.000",
  "producer": "eosio",
  "confirmed": 0,
  "previous": "000001b760e4a6610d122c5aa5d855aa49e29f3052ac3e40b9e1ef78e0f1fd02",
  "transaction_mroot": "32cb43abd7863f162f4d8f3ab9026623ea99d3f8261d2c8b4d8bf920ab97e3d1",
  "action_mroot": "09afeaf40d6988a14e9e92817d2ccf4023b280075c99f13782a6535ccc58cbb0",
  "schedule_version": 0,
  "new_producers": null,
  "header_extensions": [],
  "producer_signature": "SIG_K1_K2eFDzbxCg3hmQzpzPuLYmiesrciPmTHdeNsQDyFgcHUMFeMC3PntXTqiup5VuNmyb7qmH18FBdMuNKsc7jgCm1TSPFbaj",
  "transactions": [{
      "status": "executed",
      "cpu_usage_us": 290,
      "net_usage_words": 16,
      "trx": {
        "id": "d74843749d1e255f13572b7a3b95af9ddd6df23d1d0ad19d88e1496091d4be2b",
        "signatures": [
          "SIG_K1_KVzwg3QRH6ZmempNsvAxpPQa42hF4tDpV5cqwqo7EY4oSU7NMrEFwG7gdSDCnUHHhmH1EwtVAmV1z9bqtTvvQNSXiSgaWG"
        ],
        "compression": "none",
        "packed_context_free_data": "",
        "context_free_data": [],
        "packed_trx": "8497725bb601973ea96f0000000100408c7a02ea3055000000000085269d000706686168616861010082c95865ea3055000000000000806b010082c95865ea305500000000a8ed3232080000000000d08cf200",
        "transaction": {
          "expiration": "2018-08-14T08:49:08",
          "ref_block_num": 438,
          "ref_block_prefix": 1873362583,
          "max_net_usage_words": 0,
          "max_cpu_usage_ms": 0,
          "delay_sec": 0,
          "context_free_actions": [{
              "account": "eosio.null",
              "name": "nonce",
              "authorization": [],
              "data": "06686168616861"
            }
          ],
          "actions": [{
              "account": "eosiotesta1",
              "name": "hi",
              "authorization": [{
                  "actor": "eosiotesta1",
                  "permission": "active"
                }
              ],
              "data": {
                "user": "yeah"
              },
              "hex_data": "0000000000d08cf2"
            }
          ],
          "transaction_extensions": []
        }
      }
    }
  ],
  "block_extensions": [],
  "id": "000001b8d299602b289a9194bd698476c5d39c5ad88235460908e9d43d04edc8",
  "block_num": 440,
  "ref_block_prefix": 2492570152
}

//lets also push a context free action, the multi chain test will then also include a context free action
("context_free_actions", fc::variants({
    fc::mutable_variant_object()
       ("account", name(config::null_account_name))
       ("name", "nonce")
       ("data", fc::raw::pack(v))
    })
 )

A账户转账给B账户100个SYS，如何查看A账户的余额？

cleos create key
cleos wallet import 5JA9oDotJHoKnjUV6NrAMx4g5gWTCVCRLybTnG1XVU3EKGZZeNY
cleos wallet import --private-key 5JA9oDotJHoKnjUV6NrAMx4g5gWTCVCRLybTnG1XVU3EKGZZeNY
cleos wallet keys
cleos wallet import --private-key 5KQwrPbwdL6PhXujxW37FSSQZ1JiwsST4cqQzDeyXtP79zkvFD3
cleos wallet keys
cleos create account eosio usertesta1 EOS761KfjhYy3FSypZGG5hePrR8K2wzmw75JCDXgypKt2DLXZoZPW
cleos create account eosio eosio.token EOS761KfjhYy3FSypZGG5hePrR8K2wzmw75JCDXgypKt2DLXZoZPW
cleos set contract eosio.token work/src/github.com/eos/build/contracts/eosio.token/
cleos push action eosio.token create '["eosio","100000000.0000 SYS"]'
cleos push action eosio.token issue 
cleos push action eosio.token issue '["usertesta1","10000000.0000 SYS"]' -p eosio.token
cleos push action eosio.token issue '["usertesta1","10000000.0000 SYS"]' -p eosio
cleos get currency balance eosio.token usertesta1
cleos get table eosio.token usertesta1 accounts
cleos get table eosio.token eosio accounts

{
    "account": "eosiotesta1",
    "name": "hi",
    "authorization": [{
      "actor": "eosiotesta1",
      "permission": "active"
    }],
    "data": {
    "user": "yeah"
    },
    "hex_data": "0000000000d08cf2"
}

    很多人搞不明白为什么区块链不可篡改，却在StateDB中好像可以修改还能删除？

曾经我们要定义一个系统启动时自启动服务的方式是在/etc/init.d 目录下写一个脚本来执行，现在在ubuntu的服务模式下，我们可以丢弃那种方式，服务模式的命令是service，而现在的ubuntu系统推崇使用的systemctl命令，他俩的使用方法的区别就在于参数的顺序。

    sudo vi /etc/systemd/system/mongodb.service

[Unit]
Description=High-performance, schema-free document-oriented database
After=network.target
 
[Service]
User=mongodb
ExecStart=['mongod' command location] --quiet --config /etc/mongod.conf
 
[Install]
WantedBy=multi-user.target

    systemctl list-unit-files

    systemctl is-enabled mongodb

    sudo systemctl enable mongodb

    sudo systemctl start mongodb

    sudo systemctl status mongodb

    sudo systemctl stop mongodb

set(BUILD_MONGO_DB_PLUGIN "true")