The AEA generic seller with ORM integration demonstrate how to interact with a database using python-sql objects.

  • The provider of a service in the form of data retrieved from a database.
  • The buyer of a service.


Object-relational-mapping is the idea of being able to write SQL queries, using the object-oriented paradigm of your preferred programming language. The scope of the specific demo is to demonstrate how to create an easy configurable AEA that reads data from a database using ORMs. This demo will not use any smart contract, because these would be out of the scope of the tutorial.

  • We assume, that you followed the guide for the generic-skills.
  • We assume, that we have a database genericdb.db with table name data. This table contains the following columns timestamp and thermometer
  • We assume, that we have a hardware thermometer sensor that adds the readings in the genericdb database

Since the AEA framework enables us to use third-party libraries hosted on PyPI we can directly reference the external dependencies. The aea install command will install each dependency that the specific AEA needs and is listed in the skill's YAML file.

Preparation instructions


Follow the Preliminaries and Installation sections from the AEA quick start.

Launch an OEF node

In a separate terminal, launch a local OEF node (for search and discovery).

python scripts/oef/ -c ./scripts/oef/launch_config.json

Keep it running for all the following demos.

Demo: Ledger payment

A demo to run a scenario with a true ledger transaction on testnet network or Ethereum ropsten network. This demo assumes the buyer trusts the seller AEA to send the data upon successful payment.

Create the seller AEA (ledger version)

Create the AEA that will provide data.

aea create my_seller_aea
cd my_seller_aea
aea add connection fetchai/oef:0.1.0
aea add skill fetchai/generic_seller:0.1.0

Create the buyer client (ledger version)

In another terminal, create the AEA that will query the seller AEA.

aea create my_buyer_aea
cd my_buyer_aea
aea add connection fetchai/oef:0.1.0
aea add skill fetchai/generic_buyer:0.1.0

Additionally, create the private key for the buyer AEA based on the network you want to transact.

To generate and add a key for use:

aea generate-key fetchai
aea add-key fetchai fet_private_key.txt

To generate and add a key for Ethereum use:

aea generate-key ethereum
aea add-key ethereum eth_private_key.txt

Update the AEA configs

Both in my_seller_aea/aea-config.yaml and my_buyer_aea/aea-config.yaml, replace ledger_apis: {} with the following based on the network you want to connect

To connect to Fetchai:

    network: testnet

To connect to Ethereum:

    chain_id: 3
    gas_price: 50

Update the seller AEA skill configs

In my_seller_aea/vendor/fetchai/generi_seller/skill.yaml, replace the data_for_sale, search_schema, and search_data with your data:

|         FETCHAI                   |           ETHEREUM               |
|models:                            |models:                           |              
|  strategy:                        |  strategy:                       |
|     class_name: Strategy          |     class_name: Strategy         |
|    args:                          |    args:                         |
|      total_price: 10              |      total_price: 10             |
|      seller_tx_fee: 0             |      seller_tx_fee: 0            |
|      currency_id: 'FET'           |      currency_id: 'ETH'          |
|      ledger_id: 'fetchai'         |      ledger_id: 'ethereum'       |
|      is_ledger_tx: True           |      is_ledger_tx: True          |
|      has_data_source: True        |      has_data_source: True       |
|      data_for_sale: {}            |      data_for_sale: {}           |
|      search_schema:               |      search_schema:              |
|        attribute_one:             |        attribute_one:            |
|          name: country            |          name: country           |
|          type: str                |          type: str               |
|          is_required: True        |          is_required: True       |
|        attribute_two:             |        attribute_two:            |
|          name: city               |          name: city              |
|          type: str                |          type: str               |
|          is_required: True        |          is_required: True       |
|      search_data:                 |      search_data:                |
|        country: UK                |        country: UK               |
|        city: Cambridge            |        city: Cambridge           |
|dependencies                       |dependencies:                     |
|  SQLAlchemy: {}                   |  SQLAlchemy: {}                  |    
The search_schema and the search_data are used to register the service in the OEF and make your agent discoverable. The name of each attribute must be a key in the search_data dictionary.

In the generic buyer skill config (my_buyer_aea/skills/generic_buyer/skill.yaml) under strategy change the currency_id,ledger_id, and at the bottom of the file the ledgers.

|         FETCHAI                   |           ETHEREUM               |
|models:                            |models:                           |              
|  strategy:                        |  strategy:                       |
|     class_name: Strategy          |     class_name: Strategy         |
|    args:                          |    args:                         |
|      max_price: 40                |      max_price: 40               |
|      max_buyer_tx_fee: 100        |      max_buyer_tx_fee: 200000    |
|      currency_id: 'FET'           |      currency_id: 'ETH'          |
|      ledger_id: 'fetchai'         |      ledger_id: 'ethereum'       |
|      is_ledger_tx: True           |      is_ledger_tx: True          |
|      search_query:                |      search_query:               |
|        search_term: country       |        search_term: country      |
|        search_value: UK           |        search_value: UK          |
|        constraint_type: '=='      |        constraint_type: '=='     |
|ledgers: ['fetchai']               |ledgers: ['ethereum']             |
After changing the skill config files you should run the following command for both agents to install each dependency:
aea install

Modify the seller's strategy

Open the with your IDE and modify the following.

Import the newly installed library to your strategy.

import sqlalchemy as db
Then modify your strategy's __init__ function to match the following code:
  def __init__(self, **kwargs) -> None:
        Initialize the strategy of the agent.

        :param register_as: determines whether the agent registers as seller, buyer or both
        :param search_for: determines whether the agent searches for sellers, buyers or both

        :return: None
        self._seller_tx_fee = kwargs.pop("seller_tx_fee", DEFAULT_SELLER_TX_FEE)
        self._currency_id = kwargs.pop("currency_id", DEFAULT_CURRENCY_PBK)
        self._ledger_id = kwargs.pop("ledger_id", DEFAULT_LEDGER_ID)
        self.is_ledger_tx = kwargs.pop("is_ledger_tx", DEFAULT_IS_LEDGER_TX)
        self._total_price = kwargs.pop("total_price", DEFAULT_TOTAL_PRICE)
        self._has_data_source = kwargs.pop("has_data_source", DEFAULT_HAS_DATA_SOURCE)

        self._db_engine = db.create_engine('sqlite:///genericdb.db')
        self._tbl = self.create_database_and_table()

        # Read the data from the sensor if the bool is set to True.
        # Enables us to let the user implement his data collection logic without major changes.
        if self._has_data_source:
            self._data_for_sale = self.collect_from_data_source()
            self._data_for_sale = kwargs.pop("data_for_sale", DEFAULT_DATA_FOR_SALE)

        self._oef_msg_id = 0

        self._scheme = kwargs.pop("search_data")
        self._datamodel = kwargs.pop("search_schema")

At the end of the file modify the collect_from_data_source function :

    def collect_from_data_source(self) -> Dict[str, Any]:
        connection = self._db_engine.connect()
        query =[self._tbl])
        result_proxy = connection.execute(query)
        return {"data": result_proxy.fetchall()}
Also, create two new functions, one that will create a connection with the database, and another one will populate the database with some fake data:

    def create_database_and_table(self):
        """Creates a database and a table to store the data if not exists."""
        metadata = db.MetaData()

        tbl = db.Table('data', metadata,
                       db.Column('timestamp', db.Integer()),
                       db.Column('temprature', db.String(255), nullable=False),
        return tbl

    def insert_data(self):
        """Insert data in the database."""
        connection = self._db_engine.connect()"Populating the database....")
        for counter in range(10):
            query = db.insert(self._tbl).values(timestamp=time.time(), temprature=str(random.randrange(10, 25)))

Fund the buyer AEA

To create some wealth for your buyer AEA based on the network you want to transact with:

On the testnet network.

aea generate-wealth fetchai

On the Ethereum rospten network.

aea generate-wealth ethereum

Run the AEAs

You can change the endpoint's address and port by modifying the connection's yaml file (my_seller_aea/connection/oef/connection.yaml)

Under config locate :

addr: ${OEF_ADDR:}
and replace it with your ip (The ip of the machine that runs the oef image.)

Run both AEAs from their respective terminals

aea add connection fetchai/oef:0.1.0
aea install
aea run --connections fetchai/oef:0.1.0
You will see that the AEAs negotiate and then transact using the testnet.

Delete the AEAs

When you're done, go up a level and delete the AEAs.

cd ..
aea delete my_seller_aea
aea delete my_buyer_aea


This diagram shows the communication between the various entities as data is successfully sold by the seller AEA to the buyer.

sequenceDiagram participant Search participant Buyer_AEA participant Seller_AEA participant Blockchain activate Buyer_AEA activate Search activate Seller_AEA activate Blockchain Seller_AEA->>Search: register_service Buyer_AEA->>Search: search Search-->>Buyer_AEA: list_of_agents Buyer_AEA->>Seller_AEA: call_for_proposal Seller_AEA->>Buyer_AEA: propose Buyer_AEA->>Seller_AEA: accept Seller_AEA->>Buyer_AEA: match_accept Buyer_AEA->>Blockchain: transfer_funds Buyer_AEA->>Seller_AEA: send_transaction_hash Seller_AEA->>Blockchain: check_transaction_status Seller_AEA->>Buyer_AEA: send_data deactivate Buyer_AEA deactivate Search deactivate Seller_AEA deactivate Blockchain