Part 2: Local Chains

Introduction

In part 1 of the tutorial we modified our Greeter contract and expanded the test suite to cover the new functionality.

In this portion of the tutorial we will explore the ability for populus to both run nodes for you as well as connect to running nodes.

Setting up a local chain

The first thing we will do is setup a local chain. Create a file in the root of your project named populus.json with the following contents

{
  "version": "3",
  "chains": {
    "horton": {
      "chain": {
        "class": "populus.chain.geth.LocalGethChain"
      },
      "web3": {
        "provider": {
          "class": "web3.providers.ipc.IPCProvider"
        }
      },
      "contracts": {
        "backends": {
          "JSONFile": {"$ref": "contracts.backends.JSONFile"}
        }
      }
    }
  }
}

We have just setup the minimal configuration necessary to run a local chain named horton. You can run this chain now in yoru terminal with the following command.

$ populus chain run horton

You should see alot of very verbose output from the running geth node. If you wait and watch you will also see blocks being mined.

Deploying the contract

Now that we have a local chain we can deploy our Greeter contract using the populus deploy command. When prompted select the listed account.

$ populus deploy --chain horton Greeter
Beginning contract deployment.  Deploying 1 total contracts (1 Specified, 0 because of library dependencies).

Greeter
Accounts
-----------------
0 - 0xf142ff9061582b7b5f2f39f1be6445947a1f3feb

Enter the account address or the number of the desired account [0xf142ff9061582b7b5f2f39f1be6445947a1f3feb]: 0
Deploying Greeter
Deploy Transaction Sent: 0xd3e6ad1ee455b37bd18703a6686575e9471101fbed7aa21808afd0495e026fe6
Waiting for confirmation...

Transaction Mined
=================
Tx Hash      : 0xce71883741bf4a86e2ca5dd0be5e99888e09888b8a40361a9fb1df81210abe10
Address      : 0x89c2a280a483f45a3d140ef752ffe9c6cd4b57fa
Gas Provided : 433940
Gas Used     : 333940


Verifying deployed bytecode...
Verified contract bytecode @ 0x89c2a280a483f45a3d140ef752ffe9c6cd4b57fa matches expected runtime bytecode
Deployment Successful.

Note

Your output will differ in that the ethereum address and transaction hashes won’t be the same.

It’s worth pointing out some special properties of local chains.

  • They run with all APIs enabled (RPC, IPC, WebSocket)
  • They run with the coinbase unlocked.
  • They mine blocks using a single CPU.
  • Their datadir is located in the ./chains directory within your project.
  • The coinbase account is alotted a lot of ether.

Having to select which account to deploy from each time you deploy on a chain is tedious. Lets modify our configuration to specify what the default deploy address should be. Change your configuration to match this.

{
  "version": "3",
  "chains": {
    "horton": {
      "chain": {
        "class": "populus.chain.LocalGethChain"
      },
      "web3": {
        "provider": {
          "class": "web3.providers.ipc.IPCProvider"
        },
        "eth": {
          "default_account": "0xf142ff9061582b7b5f2f39f1be6445947a1f3feb"
        }
      }
    }
  }
}

You can test this now by deploying the greeter contract again using the same command from above. If everything is configured correctly you should no longer be prompted to select an account.

Connecting to a testrpc node

First, install eth-testrpc:

$ pip install eth-testrpc

After installation, run:

$ testrpc-py

Available Accounts
==================
0x82a978b3f5962a5b0957d9ee9eef472ee55b42f1
0x7d577a597b2742b498cb5cf0c26cdcd726d39e6e
0xdceceaf3fc5c0a63d195d69b1a90011b7b19650d
0x598443f1880ef585b21f1d7585bd0577402861e5
0x13cbb8d99c6c4e0f2728c7d72606e78a29c4e224
0x77db2bebba79db42a978f896968f4afce746ea1f
0x24143873e0e0815fdcbcffdbe09c979cbf9ad013
0x10a1c1cb95c92ec31d3f22c66eef1d9f3f258c6b
0xe0fc04fa2d34a66b779fd5cee748268032a146c0
0x90f0b1ebbba1c1936aff7aaf20a7878ff9e04b6c

Listening on localhost:8545

Note

Make sure that you are actually running python testrpc, not the javascript version.

Then add some new configs to populus.json:

{
  "chains": {

    ...

    "local": {
      "chain": {
        "class": "populus.chain.ExternalChain"
      },
      "contracts": {
        "backends": {
          "Memory": {
            "$ref": "contracts.backends.Memory"
          },
          "ProjectContracts": {
            "$ref": "contracts.backends.ProjectContracts"
          },
          "TestContracts": {
            "$ref": "contracts.backends.TestContracts"
          }
        }
      },
      "web3": {
        "$ref": "web3.Local"
      }
    }
  }

  ...

  "web3": {

    ...

    "Local": {
      "provider": {
        "class": "web3.providers.rpc.HTTPProvider",
        "settings": {
          "endpoint_uri": "http://localhost:8545"
        }
      }
    }
  }
}

Now, deploy the contract to testrpc node:

$ populus deploy --chain local --no-wait-for-sync Greeter

> Found 1 contract source files
  - contracts/Greeter.sol
> Compiled 1 contracts
  - contracts/Greeter.sol:Greeter
Beginning contract deployment.  Deploying 1 total contracts (1 Specified, 0 because of library dependencies).

Greeter
Deploying Greeter
Deploy Transaction Sent:
0x7eddc9a2b6e866388de4a7f029fa39030d752d72cc9e602cfb71d4257bb8d1e8
Waiting for confirmation...

Transaction Mined
=================
Tx Hash      :
0x7eddc9a2b6e866388de4a7f029fa39030d752d72cc9e602cfb71d4257bb8d1e8
Address      : 0xc305c901078781c232a2a521c2af7980f8385ee9
Gas Provided : 469607
Gas Used     : 369607


Verified contract bytecode @ 0xc305c901078781c232a2a521c2af7980f8385ee9
Deployment Successful.

Note

The output address 0xc305c901078781c232a2a521c2af7980f8385ee9 will be used later to verify contract deployment.

And you should see these logs from testrpc node:

127.0.0.1 - - [02/Sep/2017 14:55:06] "POST / HTTP/1.1" 200 48
127.0.0.1 - - [02/Sep/2017 14:55:06] "POST / HTTP/1.1" 200 44
127.0.0.1 - - [02/Sep/2017 14:55:06] "POST / HTTP/1.1" 200 2414
127.0.0.1 - - [02/Sep/2017 14:55:06] "POST / HTTP/1.1" 200 107
127.0.0.1 - - [02/Sep/2017 14:55:06] "POST / HTTP/1.1" 200 3071
127.0.0.1 - - [02/Sep/2017 14:55:06] "POST / HTTP/1.1" 200 391
127.0.0.1 - - [02/Sep/2017 14:55:06] "POST / HTTP/1.1" 200 391
127.0.0.1 - - [02/Sep/2017 14:55:06] "POST / HTTP/1.1" 200 2163
127.0.0.1 - - [02/Sep/2017 14:55:06] "POST / HTTP/1.1" 200 2164

Finally, use web3.py to check if the contract is successfully deployed. This is done by checking if the given contract address 0xc305c901078781c232a2a521c2af7980f8385ee9 has corresponding bytecode:

$ pip install web3

>>> from web3 import Web3, HTTPProvider, IPCProvider
>>> web3 = Web3(HTTPProvider('http://localhost:8545'))
>>> web3.eth.getCode("0xc305c901078781c232a2a521c2af7980f8385ee9")

u'0x60606040526000357c....