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Python components

cd pyspark

Client-side interaction with the blockchain​

The BlockchainClient class utilizes the NetworkSettings class to establish a connection to the blockchain node. This includes parameters such as node URLs, retry intervals, and failover strategies.

./seed_products.py
        settings = NetworkSettings(
            node_url_pool=[os.getenv("POSTCHAIN_TEST_NODE", "http://localhost:7740")],
            status_poll_interval=int(os.getenv("STATUS_POLL_INTERVAL", "500")), # Opitional parameter
            status_poll_count=int(os.getenv("STATUS_POLL_COUNT", "5")), # Opitional parameter
            verbose=True, # Opitional parameter
            attempt_interval=int(os.getenv("ATTEMPT_INTERVAL", "5000")), # Opitional parameter
            attempts_per_endpoint=int(os.getenv("ATTEMPTS_PER_ENDPOINT", "3")), # Opitional parameter
            failover_strategy=FailoverStrategy.ABORT_ON_ERROR, # Opitional parameter
            unreachable_duration=int(os.getenv("UNREACHABLE_DURATION", "30000")), # Opitional parameter
            use_sticky_node=False, # Opitional parameter
            blockchain_iid=int(os.getenv("BLOCKCHAIN_IID", "0")) # Opitional parameter

        )
        # Create blockchain client
        client = await BlockchainClient.create(settings)
}

seed_products function builds and sends a blockchain transaction to create a product in the database of the node .

./seed_products.py
async def seed_products(client: BlockchainClient):
    """Example of how to create and send a transaction"""
    try:

        # Create private/public key pair
        private_bytes = bytes.fromhex(os.getenv("PRIV_KEY"))
        private_key = PrivateKey(private_bytes, raw=True)
        public_key = private_key.pubkey.serialize()
        
        # Create operation
        operation = Operation(
            op_name="seed_data",
            args=[]
        )
        
        # Create transaction
        transaction = Transaction(
            operations=[operation],
            signers=[public_key],
            signatures=None,
            blockchain_rid=client.config.blockchain_rid
        )
        
        # Sign the transaction
        signed_transaction = await client.sign_transaction(
            transaction,
            private_bytes
        )
        
        # Send transaction and wait for confirmation
        receipt = await client.send_transaction(
            signed_transaction,
            do_status_polling=True
        )
        
        print(f"\nTransaction status: {receipt.status}")
        if receipt.status == ResponseStatus.CONFIRMED:
            print("Transaction confirmed!")
        else:
            print(f"Transaction failed: {receipt.message}")
            
    except Exception as e:
        print(f"Transaction failed: {str(e)}")

get_products_paginated function retrieves products from the database paginataed.

./get_products_paginated.py
async def get_products_paginated(client: BlockchainClient, cursor: None):
    """Example of how to query the blockchain"""
    try:
        return await client.query("get_products_paginated", 
            {"page_size": 1000, "page_cursor": cursor})
    except Exception as e:
        print(f"Query failed: {str(e)}")

This codesnippet demomstates how to use the query with pagination. The main idea is to call the query in the loop until cursor equals to None.

./get_products_paginated.py
        products_all = []
        products = await get_products_paginated(client, None)
        products_all = products_all + products['data']
        while products['next_cursor'] != None:
            products = await get_products_paginated(client, products['next_cursor'])
            products_all = products_all + products['data']