EOS Demux using PostgreSQL

I have been looking for EOS demux implementation using PostgreSQL but found none. So I thought of writing this short tutorial explaining how we can implement EOS demux using PostgreSQL. Those who don’t know about EOS Demux please have a look at the article explaining the same in a very intuitive way.  https://github.com/EOSIO/demux-js.


A short explanation of EOS Demux: Demux architecture allows application developers to use traditional Mongo or Postgres SQL databases in a way that means the data stored in them is still verifiable by the blockchain. This enables the best of both worlds: the flexibility and speed of traditional databases, coupled with the trust and immutable properties of a blockchain. The overall flow of an application looks as follows:


To use PostgreSQL as a data store we need to use massive.js. So go ahead and install massive.js using the following command

> npm i massive --save
To demonstrate the working of PostgreSQL based demux implementation we are going to use a very basic contract. The contract is about a blog, using which user can do CRUD operation on the blog. As blog data is big we are going to store the blog data into PostgreSQL and metadata related to the blog like user, email etc. will be a part of the blockchain. Blockchain maintains all the information which
are required to make blog entry verifiable and secure. Following is the contract.
#include <eosiolib/eosio.hpp>

#include <eosiolib/multi_index.hpp>

#include <eosiolib/types.hpp>

#include <eosiolib/print.hpp>

#include <eosiolib/system.h>

//using namespace eosio;

class blog_contract : public eosio::contract{


    blog_contract(account_name self) : eosio::contract(self),

          bloges(self, self){}

        /// @abi action

        void create(account_name author, uint64_t id, std::string email, const std::string& data){


            blogs.emplace(author, [&](auto& new_blog) {

                new_blog.id = id;

                new_blog.author = author;



        //.. destroy, show and update actions .. 

    private :

        /// @abi table blog i64

        struct blog{

            uint64_t id;

            uint64_t author;

            uint64_t primary_key() const {

                return id;




        typedef eosio::multi_index<N(blog), blog> blog_table;

        blog_table blogs;


EOSIO_ABI( blog_contract, (create)(destroy)(show)(update) )
If you look closely at ‘create’ function of the contract, you would notice that the function’s signature contains blog data as one of the parameters but we are not storing the blog data as part of EOS’ database. The purpose of having blog data as part of the function signature is that it gets available to be stored in PostgreSQL. Whatever we mentioned as function parameters, those parameter’s data will be available to the action handler. Looking at the diagram ‘Action watcher’ keeps looking for any change in blockchain via ‘Action Reader’. Whenever there is any action happened in the Blockchain, Action watcher delegate that action to ‘Action Handler’. Then ‘Action Handler’ further calls ‘updaters’ and ‘effects’ which actually execute necessary action code. Based upon the discussion the configuration looks as follows:
//First get the postgreSQL instance via massive as follows:
const massive = require('massive');

let db;

 host: host,
 port: port,
 database: database, 
 user: user,
 password: password 
}).then(instance => {
 db = instance;
 return Promise.resolve(db);
}).catch(e => {
 console.log('error while getting massive instance')
Let’s define Updaters and Effects
function createBlog(db, payload, blockInfo, context){
 id : payload.data.id,
 author : payload.data.author,
 data : payload.data.data, //Storing blog data
 email : payload.data.email
 }).then(new_blog => {
 console.log('blog created')
 }).catch(err => {
 console.log('error while inserting data')

//Register blockchain Actions to which this update will be called.

const updaters = [{
 actionType: "blogger.p::create",
 updater: createProfile}

module.exports = updaters
function logUpdate(state, payload, blockInfo, context) {
 console.info(“blog created\n")
const effects = [
 actionType: "blogger.p::create",
 effect: logUpdate,

module.exports = effects
Now create MassiveActionHandler, Action Reader, and Action Watcher as follows:
const {
 readers: {
 eos: { NodeosActionReader }
 handlers :{
 postgres : { MassiveActionHandler }
 watchers: { BaseActionWatcher }
 } = require('demux-js')

const actionHandler = new MassiveActionHandler(

const actionReader = new NodeosActionReader(
 0, // Start at most recent blocks

const actionWatcher = new BaseActionWatcher(
You also need to make sure the following table exists in PostgreSQL, which keeps track of block number up to which action has already been taken.
CREATE TABLE _index_state (
 id serial PRIMARY KEY,
 block_number integer NOT NULL,
 block_hash text NOT NULL,
 is_replay boolean NOT NULL

Hacking ethereum to inject our own consensus alogrithm Part-2

This is the second blog post for hacking Ethereum. If you have not gone through the first blog post please click here and have your local environment set up. The main entry point for Ethereum is /go-ethereum/cmd/geth/main.go

Open up main.go and look at ‘main’ method, which is the entry point whenever we execute ./geth binary.  This function basically executes the application with whatever command parameter we have supplied to it. As we know in ‘go’ there is specific function ‘init’ which gets executed before calling the module, let’s see what’s inside in initialisation code. The important line to notice is:


app.Action = geth


So default action if we don’t supply any via command line parameter is geth. ‘geth’ is a function inside main.go. This function is actually starting up all background services for a node.


func geth(ctx *cli.Context) error {

node := makeFullNode(ctx)

startNode(ctx, node)


return nil



Let further analyse the function ‘makeFullNode(ctx)’. Go to its implementation, we see at 2nd line  “utils.RegisterEthService(stack, &cfg.Eth)”

It is registering “eth” service using utils. As we are running full node following is the code which actually gets executed:


func RegisterEthService(stack *node.Node, cfg *eth.Config) {


err = stack.Register(func(ctx *node.ServiceContext) (node.Service, error) {

fullNode, err := eth.New(ctx, cfg)

if fullNode != nil && cfg.LightServ > 0 {

ls, _ := les.NewLesServer(fullNode, cfg)



return fullNode, err




This function is registering new service to the stack which is basically a node. It means whenever we start a node this service will be executed. Let’s analyse the line fullNode, err := eth.New(ctx, cfg)


Going to the implementation of the ‘eth.New’ we go to ‘backend.go’ file. Looking at the constructor code, this service is nothing but Ethereum service. This constructor function configures the whole Ethereum. As our goal for this tutorial is to change the consensus algorithm following is the code of interest under ‘backend.go -> func New’


eth := &Ethereum{

config: config,

chainDb: chainDb,

chainConfig: chainConfig,

eventMux: ctx.EventMux,

accountManager: ctx.AccountManager,

engine: CreateConsensusEngine(ctx, &config.Ethash, chainConfig, chainDb),

shutdownChan: make(chan bool),

networkID: config.NetworkId,

gasPrice: config.GasPrice,

etherbase: config.Etherbase,

bloomRequests: make(chan chan *bloombits.Retrieval),

bloomIndexer: NewBloomIndexer(chainDb, params.BloomBitsBlocks),

So the code where we need to make changes is CreateConsensusEngine. Looking at the code it is clear that if we want to have our own consensus algorithm we need to implement ‘engine’ interface. Go to location ‘go-ethereum/consensus/‘ and created a new directory ‘myalgo’. Let’s make a very simple class (consensus algorithm) which will just print the message at various stages of consensus workflow. After that, we will extend it into the more advanced algorithm. For this we need to create two files ‘myalgo.go’ and ‘api.go’ under location ‘go-ethereum/consensus/myalgo’. You can look at those files from GitHub, the content which is important for us to discuss further is listed below:
func (MyAlgo *MyAlgo) VerifyHeader(chain consensus.ChainReader, header *types.Header, seal bool) error {

log.Info("will verfiyHeader")

return nil

func (MyAlgo *MyAlgo) VerifyHeaders(chain consensus.ChainReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error){

log.Info("will verfiyHeaders")

abort := make(chan struct{})

results := make(chan error, len(headers))
go func() {

for _, header := range headers {

err := MyAlgo.VerifyHeader(chain, header, false)

select {

case <-abort:


case results <- err:




return abort, results

func (MyAlgo *MyAlgo) VerifyUncles(chain consensus.ChainReader, block *types.Block) error {

log.Info("will verfiy uncles")

return nil

func (MyAlgo *MyAlgo) VerifySeal(chain consensus.ChainReader, header *types.Header) error{

log.Info("will verfiy VerifySeal")

return nil

func (MyAlgo *MyAlgo) Prepare(chain consensus.ChainReader, header *types.Header) error{

log.Info("will prepare the block")

parent := chain.GetHeader(header.ParentHash, header.Number.Uint64()-1)

if parent == nil {

return consensus.ErrUnknownAncestor

header.Difficulty = MyAlgo.CalcDifficulty(chain, header.Time.Uint64(), parent)

return nil

func (MyAlgo *MyAlgo) CalcDifficulty(chain consensus.ChainReader, time uint64, parent *types.Header) *big.Int {

return calcDifficultyHomestead(time, parent)

func (MyAlgo *MyAlgo) Finalize(chain consensus.ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction,

uncles []*types.Header, receipts []*types.Receipt) (*types.Block, error){

log.Info("will Finalize the block")

header.Root = state.IntermediateRoot(chain.Config().IsEIP158(header.Number))

b := types.NewBlock(header, txs, uncles, receipts)

return b, nil

func (MyAlgo *MyAlgo) Seal(chain consensus.ChainReader, block *types.Block, stop <-chan struct{}) (*types.Block, error){

log.Info("will Seal the block")

//time.Sleep(15 * time.Second)

header := block.Header()

header.Nonce, header.MixDigest = getRequiredHeader()

return block.WithSeal(header), nil


As you can see most of them are just dummy function, always returning success result. In this algorithm, we are not actually finding any nonce, so after plugging this consensus algorithm it is expected that block is generated in an infinite loop without any delay. Let’s plug this algorithm and see what we are getting in logs. To plug this algorithm in Ethereum insert following code to “CreateConsensusEngine” function in ‘go-ethereum/eth/backend.go’ file.


if chainConfig.MyAlgo != nil{

fmt.Println(“myalgo is configured as consensus engine")

return myalgo.New(chainConfig.MyAlgo, db)



So this method basically checks if we have configured our configuration to use ‘MyAlgo’ or not. To enable ‘MyAlgo’ we need to make changes to our ‘privategensis.json’, Replace the content of the file with the following:



"config": {

"chainId": 15,

"homesteadBlock": 0,

"eip155Block": 0,

"eip158Block": 0,

"myalgo" : {}


"difficulty": "2000000",

"gasLimit": "21000000",

"alloc": {




Note the additional change “myalgo:{}” this line will enable our algorithm instead of default one. Delete previously create a directory from tutorial-1 and initialise Ethereum with new configuration:


> rm -rf ~/.ethereum/myprivatenet
> ./geth --datadir ~/.ethereum/myprivatenet init privategensis.json


Start the node as we did previously in the last tutorial. You will notice some additional logs and module after starting the node:


INFO [06-21|16:49:41.400938] Starting P2P networking


myalgo is configured as consensus engine

INFO [06-21|16:49:43.658541] UDP listener up self=enode://f08e5aa4fbde25b09ee977001af4a642abfd150c47e571ec5b69deed8c8c644c0a785d47a890adb6b2b55155cd32d7c035f4ec3ce7f8af54cd07219c8ad06ee7@[::]:30301

INFO [06-21|16:49:43.658717] RLPx listener up self=enode://f08e5aa4fbde25b09ee977001af4a642abfd150c47e571ec5b69deed8c8c644c0a785d47a890adb6b2b55155cd32d7c035f4ec3ce7f8af54cd07219c8ad06ee7@[::]:30301

INFO [06-21|16:49:43.661563] IPC endpoint opened url=/Users/hemants/.ethereum/myprivatenet/geth.ipc

INFO [06-21|16:49:43.662937] HTTP endpoint opened url=http://localhost:8101 cors=http://localhost:8000 vhosts=localhost

Welcome to the Geth JavaScript console!
instance: Geth/v1.8.12-unstable/darwin-amd64/go1.9.2
modules: admin:1.0 debug:1.0 eth:1.0 miner:1.0 myalgo:1.0 net:1.0 personal:1.0 rpc:1.0 txpool:1.0 web3:1.0


Log message: myalgo is configured as consensus engine, confirm that our configuration has been picked up and now Ethereum is configured with our own consensus algorithm. Also, a new module gets added to the console, it means we can interact with our consensus algorithm from the console. Great !!. This ‘myalgo’ got added due to the following two changes:


In consensus/myalgo/api.go:
type API struct {

chain consensus.ChainReader

myAlgo *MyAlgo


func (api *API) EchoNumber(ctx context.Context, number uint64) (uint64, error) {

fmt.Println("called echo number")

return number, nil

In internal/web3ext/web3ext.go:
var Modules = map[string]string{

"admin": Admin_JS,


"txpool": TxPool_JS,

"myalgo": MyAlgo_JS,


const MyAlgo_JS = `


property: 'myalgo',

methods: [

new web3._extend.Method({

name: 'echoNumber',

call: 'myalgo_echoNumber',

params: 1,

inputFormatter: [null]





This ‘echoNumber’ function is just echoing whatever we pass as an input parameter. This is to just show how we can add our own custom console modules.


> myalgo


echoNumber: function()


> myalgo.echoNumber(5)

called echo number



Now let’s start miner and see which function is being called from our consensus algorithm. As you start the miner you will notice that instantly it start mining blocks, here is the log:


> miner.start(1)


> INFO [06-21|17:01:52.43016] Transaction pool price threshold updated price=18000000000

INFO [06-21|17:01:52.43104] Etherbase automatically configured address=0x33954C10f5789A5914a09F0B1ef64CD26E0FA66E

INFO [06-21|17:01:52.43109] Starting mining operation

INFO [06-21|17:01:52.43113] will prepare the block

INFO [06-21|17:01:52.431516] will Finalize the block

INFO [06-21|17:01:52.431532] Commit new mining work number=1 txs=0 uncles=0 elapsed=406.763µs

INFO [06-21|17:01:52.431749] will Seal the block

INFO [06-21|17:01:52.431797] Successfully sealed new block number=1 hash=71810a…2882f3

INFO [06-21|17:01:52.436641] ? mined potential block number=1 hash=71810a…2882f3

INFO [06-21|17:01:52.436681] will prepare the block

INFO [06-21|17:01:52.43676] will Finalize the block

INFO [06-21|17:01:52.436768] Commit new mining work number=2 txs=0 uncles=0 elapsed=90.323µs

INFO [06-21|17:01:52.436991] will Seal the block

INFO [06-21|17:01:52.437038] Successfully sealed new block number=2 hash=b6bef3…f2ed9b

INFO [06-21|17:01:52.437498] ? mined potential block number=2 hash=b6bef3…f2ed9b

INFO [06-21|17:01:52.437641] Mining too far in the future wait=2s

INFO [06-21|17:01:54.441536] will prepare the block

INFO [06-21|17:01:54.441837] will Finalize the block

INFO [06-21|17:01:54.441891] Commit new mining work number=3 txs=0 uncles=0 elapsed=2.004s

INFO [06-21|17:01:54.442025] will Seal the block

INFO [06-21|17:01:54.442176] Successfully sealed new block number=3 hash=1d3448…e8ec87

INFO [06-21|17:01:54.442574] ? mined potential block number=3 hash=1d3448…e8ec87

INFO [06-21|17:01:54.442616] will prepare the block

INFO [06-21|17:01:54.442739] will Finalize the block

INFO [06-21|17:01:54.442757] Commit new mining work number=4 txs=0 uncles=0 elapsed=144.138µs

INFO [06-21|17:01:54.442807] will Seal the block


Let’s check the height of blockchain :


> web3.eth.getBlockNumber(function(e,r){ console.log(r)})


Wow in a matter of seconds 17 blocks got generated. Now we have our own private Ethereum running locally with our own consensus algorithm, That’s amazing. Now we can implement logic into consensus algorithm.


Before we started implementing our own algorithm I would like to highlight one more insight of the code. Ethereum service (backend.go) contains a miner which orchestrate two very important module “worker” and “agent”.

The role of the worker is to generate blocks or work. It collects all pending transaction and makes them part of the block. Please note that here ‘generate block’ does not mean that it mined the block, it simply means we are initialising the block structure and doing some preliminary validations or simply it generate the work. Worker first calls engine’s Prepare function, in case of ethereum’s standard algorithm (ethash), block difficulty is calculated. Then it calls the engine’s Finalize method.

Role of an agent (cpuAgent) is to do work generated by the worker. So the agent actually mines the block, by finding correct nonce in case of POW. The communication between the worker and agent is done via event. When the worker generates a block it generates an event which agent is listening to. Once agent mine the block, it generate the event which worker is listening to and worker starts creating new work for an agent to work on. This loop continues.

For this tutorial, I am planning to implement a very basic consensus algorithm. The details of which are as follows :


At Miner side


– There is a file called problems.json, which contains 10 problems to be solved by the miner. These problems are a simple arithmetic equation like “3 + 14 * 49”.

– Miner, while sealing the block, will first select the problem from problems.json based upon index which will the first character of current block’s parent hash. So if current block’s parent hash is

“0x29c9f33844df1df9d808412104f08dd318c016f7f06faad241fb0f8c79911c75” then the index to pick problem will be ‘2’ ( ignore 0x which represents hexadecimal),

“0xc4fbd0b2c6bc524794fbff7af77eb0d98ad42aa4c6a34776bc66210502e908e2” then the index to pick problem will be ‘2′ ( c in decimal is 12, so 12%10 = 2)

– Once the miner finds the problem, he will try to solve the problem and once the solution is found he put the solution in ‘nounce’ field of the block.


At Validator side


– Whenever the validator node got a block, it first selects the problem from “problems.json” using block’s parent hash as described above.

– Validator computes the solution and compares its solution with the Nonce.

– If both are equal, validator put the block in his chain, else he rejects the block.


Run Ethereum Local cluster


To run multiple nodes we just need to specify different ‘data-dir’ and different ‘rpc-port’. So to initialise node 1


./geth --datadir ~/.ethereum/myprivatenet-1 init privategensis.json

To initialise node 2


./geth --datadir ~/.ethereum/myprivatenet-2 init privategensis.json

Similarly, you can initialise as many nodes as you want.

To start node, you need to mention previously created ‘data-dir’ and port. So to start node 1


./geth -rpc -rpcapi 'web3,eth,debug,personal'  -rpcport 8545 --rpccorsdomain '*' --datadir ~/.ethereum/myprivatenet-1 --networkid 15

To start node 2


./geth -rpc -rpcapi 'web3,eth,debug,personal'  -rpcport 8546 --rpccorsdomain '*' --datadir ~/.ethereum/myprivatenet-2 --networkid 15

As of now, these two nodes are running independently without knowing each other. So to connect node1 to node1, go to geth console and find node1 enode address by issuing following command:


node1 > admin.nodeInfo.enode

This will return enode address of the node1 like


node1 > "enode://c7a9acd7a6f381bb33a51767e07989939448fae4db2ec95cc736f88bebd39c6fce1e75b333225b435a0398ff7377805b08fb8792e6a0886d855ff315e54d5cf6@[::]:30303”

Go to node2 geth console and add node1 using its enode address as follows


node2 > admin.addPeer("enode://c7a9acd7a6f381bb33a51767e07989939448fae4db2ec95cc736f88bebd39c6fce1e75b333225b435a0398ff7377805b08fb8792e6a0886d855ff315e54d5cf6@[::]:30303”)

You can check if the connection is successful or not by issue ‘net’ command. This command will return the count of connected nodes.


> net


listening: true,

peerCount: 1,

version: "1",

getListening: function(callback),

getPeerCount: function(callback),

getVersion: function(callback)



The complete code is available here: Hope I am able to give you a taste of Ethereum internals and you must be equipped enough to hack it further.

Hacking ethereum to inject our own consensus algorithum Part-1

Recently, I have been going through the source of Ethereum to see if I can change it’s proof of work consensus algorithm with our own algorithm. By doing that I developed an insight of Ethereum source code which I would like to share. The goal of this blog post is to first setup Ethereum development environment and then build very simple consensus algorithm. The consensus algorithm will be very simple as main goal of this activity is to understand the internals of Ethereum. To follow along reader is expected to be equipped with following skills:

  • Understanding of ‘go’ language : As Ethereum (geth implementation) is written in go language it is expected that you should have good grasp of language. If you are not familiar with go language it is good motivation to learn now.
  • Understanding of how blockchain works : Understanding how blockchain works in general is required. There are quite amazing blogs which explain the working of blockchain.
  • Understanding of Ethereum : You cannot hack the application if you don’t know how it works at high level. So understanding of Ethereum at high level is required.

Good development set up makes life easier for making changes to the source code. I have been using ‘goLang’ from jetBrains for a year now. It is very good IDE for go development and have very good debug support. I also use Atom IDE for small projects but for dealing big projects goLang is amazing. Following are the step you need to perform to setup development environment:

  • Make sure go is setup properly. To check if it installed on your machine or not type following command in terminal:

> go version

go version go1.9.2 darwin/amd64

If command responds with proper version, you have go installed. If it is not, install command will throw an error “ -bash: go: command not found”.

To install ‘go’, follow instruction specific to your OS platform listed here : https://golang.org/doc/install

  • Make sure GOPATH environment variable is properly set up
 > echo $GOPATH


  • Clone Ethereum GitHub repository
> cd $GOPATH/src/github.com/ 
> mkdir ethereum
> git clone git@github.com:ethereum/go-ethereum.git
  • Import Ethereum code into GoLand IDE by clicking on ‘open project’ button and locating the directory where you have checked out Ethereum code.
  • Once imported successfully run to file go-ethereum/cmd/geth/main.go, right click and run. This will report following errors:
cmd/geth/main.go:125:3: undefined: configFileFlag
cmd/geth/main.go:156:3: undefined: initCommand
cmd/geth/main.go:157:3: undefined: importCommand
cmd/geth/main.go:158:3: undefined: exportCommand
cmd/geth/main.go:159:3: undefined: importPreimagesCommand
cmd/geth/main.go:160:3: undefined: exportPreimagesCommand
cmd/geth/main.go:161:3: undefined: copydbCommand
cmd/geth/main.go:162:3: undefined: removedbCommand
cmd/geth/main.go:163:3: undefined: dumpCommand
cmd/geth/main.go:165:3: undefined: monitorCommand
cmd/geth/main.go:165:3: too many errors
  • To resolve above mentioned problem go to Run > Edit Configurations > Go Applications > select the run configuration you want to edit > Run kind and change it to File from Package. Then type the name of the package, github.com/ethereum/go-ethereum/cmd/geth and save the settings.

Our development environment is ready. Congrats !! :).

Set up local private Ethereum blockchain

To set up private Ethereum blockchain running locally, let’s first install ‘geth’ tool into $GOPATH/bin directory. To do that, open terminal and go to location $GOPATH/src/github.com/ethereum/go-ethereum, then execute following command from terminal

> go install -v ./cmd/geth

Go to location $GOPATH/bin/ to test if geth is installed properly or not. Issue following command, you should see following result.

> ./geth version

Version: 1.8.12-unstable

Architecture: amd64

Protocol Versions: [63 62]

Network Id: 1

Go Version: go1.9.2

Operating System: darwin



Next, create file name ‘privategensis.json’ with following content :


"config": {

"chainId": 15,

"homesteadBlock": 0,

"eip155Block": 0,

"eip158Block": 0


"difficulty": "2000000",

"gasLimit": "21000000",

"alloc": {



Go $GOPATH/bin and initialise local Ethereum blockchain by issue following command:

> ./geth --datadir ~/.ethereum/myprivatenet init privategensis.json
INFO [06-21|13:43:05.226227] Maximum peer count ETH=25 LES=0 total=25

INFO [06-21|13:43:05.240084] Allocated cache and file handles database=/Users/hemants/.ethereum/myprivatenet/geth/chaindata cache=16 handles=16

INFO [06-21|13:43:05.244943] Writing custom genesis block

INFO [06-21|13:43:05.245018] Persisted trie from memory database nodes=0 size=0.00B time=10.217µs gcnodes=0 gcsize=0.00B gctime=0s livenodes=1 livesize=0.00B

INFO [06-21|13:43:05.24539] Successfully wrote genesis state database=chaindata hash=07185f…82bcc4

INFO [06-21|13:43:05.245414] Allocated cache and file handles database=/Users/hemants/.ethereum/myprivatenet/geth/lightchaindata cache=16 handles=16

INFO [06-21|13:43:05.24758] Writing custom genesis block

INFO [06-21|13:43:05.247618] Persisted trie from memory database nodes=0 size=0.00B time=2.699µs gcnodes=0 gcsize=0.00B gctime=0s livenodes=1 livesize=0.00B

INFO [06-21|13:43:05.247787] Successfully wrote genesis state database=lightchaindata hash=07185f…82bcc4

This will generate the genesis block for our private blockchain at location : “/.ethereum/myprivatenet”. Lets run our blockchain by issuing following command :

./geth -rpc -rpcapi 'web3,eth,debug,personal' -rpcport 8545 --rpccorsdomain '*' --datadir ~/.ethereum/myprivatenet --networkid 15
INFO [06-21|13:49:27.007881] Maximum peer count ETH=25 LES=0 total=25

INFO [06-21|13:49:27.01546] Starting peer-to-peer node instance=Geth/v1.8.12-unstable/darwin-amd64/go1.9.2

INFO [06-21|13:49:27.015503] Allocated cache and file handles database=/Users/hemants/.ethereum/myprivatenet/geth/chaindata cache=768 handles=128

INFO [06-21|13:49:27.028411] Initialised chain configuration config="{ChainID: 15 Homestead: 0 DAO:  DAOSupport: false EIP150:  EIP155: 0 EIP158: 0 Byzantium:  Constantinople:  Engine: unknown}"

INFO [06-21|13:49:27.028465] Disk storage enabled for ethash caches dir=/Users/hemants/.ethereum/myprivatenet/geth/ethash count=3

INFO [06-21|13:49:27.028479] Disk storage enabled for ethash DAGs dir=/Users/hemants/.ethash count=2

INFO [06-21|13:49:27.028513] Initialising Ethereum protocol versions="[63 62]" network=16

INFO [06-21|13:49:27.029799] Loaded most recent local header number=0 hash=07185f…82bcc4 td=2000000

INFO [06-21|13:49:27.029836] Loaded most recent local full block number=0 hash=07185f…82bcc4 td=2000000

INFO [06-21|13:49:27.029845] Loaded most recent local fast block number=0 hash=07185f…82bcc4 td=2000000

INFO [06-21|13:49:27.03009] Loaded local transaction journal transactions=0 dropped=0

INFO [06-21|13:49:27.030331] Regenerated local transaction journal transactions=0 accounts=0

INFO [06-21|13:49:27.030806] Starting P2P networking

INFO [06-21|13:49:29.146101] UDP listener up self=enode://1dd1494242ee403a69fbb58a57505056f5fea5c9f4b207050ca0a1aecc36d74b4687ec1779320c6282d044aae0078437e5aa7688c29f04e1281cc3f5a0f954e2@[::]:30303

INFO [06-21|13:49:29.146426] RLPx listener up self=enode://1dd1494242ee403a69fbb58a57505056f5fea5c9f4b207050ca0a1aecc36d74b4687ec1779320c6282d044aae0078437e5aa7688c29f04e1281cc3f5a0f954e2@[::]:30303

INFO [06-21|13:49:29.150067] IPC endpoint opened url=/Users/hemants/.ethereum/myprivatenet/geth.ipc

INFO [06-21|13:49:29.150472] HTTP endpoint opened url=* vhosts=localhost


In logs, look for line which says “IPC endpoint opened: url=/Users/hemants/.ethereum/myprivatenet/geth.ipc”.

This url allow us to interact with blockchain via IPC channel. Copy the path and fire new terminal and go to $GOPATH/bin and execute following command to attach to IPC channel :

./geth attach /Users/hemants/.ethereum/myprivatenet/geth.ipc

Welcome to the Geth JavaScript console!

modules: admin:1.0 debug:1.0 eth:1.0 miner:1.0 net:1.0 personal:1.0 rpc:1.0 txpool:1.0 web3:1.0


With this console we can execute various commands to interact with blockchain. If you look carefully, after connecting to IPC channel, console prints out all available modules with which you can interact. Namely modules: admin:1.0 debug:1.0 eth:1.0 miner:1.0 net:1.0 personal:1.0 rpc:1.0 txpool:1.0 web3:1.0 are the modules. To see what functionality is available to use from the console just enter the module name, It will print out all the function names which we can call from the console. Like type ‘personal’ in the console it will response with following function names and properties:

> personal


listAccounts: [],

listWallets: [],

deriveAccount: function(),

ecRecover: function(),

getListAccounts: function(callback),

getListWallets: function(callback),

importRawKey: function(),

lockAccount: function(),

newAccount: function github.com/ethereum/go-ethereum/console.(*bridge).NewAccount-fm(),

openWallet: function github.com/ethereum/go-ethereum/console.(*bridge).OpenWallet-fm(),

sendTransaction: function(),

sign: function github.com/ethereum/go-ethereum/console.(*bridge).Sign-fm(),

signTransaction: function(),

unlockAccount: function github.com/ethereum/go-ethereum/console.(*bridge).UnlockAccount-fm()


Let’s call listAccounts property to see if we have any account.

> personal.listAccounts

[ ]

As expected we don’t have any account yet. So let’s create one.



Now call personal.listAccounts



Let’s check the balance in this account, It should be zero.

> eth.getBalance(personal.listAccounts[0]).toNumber()


To generated some ether we need to mine some blocks. Before mining the block we need to tell our node to run as miner node. To do that issue following command

> miner.start(1)

After some time new blocks get generated. As you are the only miner in this network you will be rewarded with ether. Lets check the balance again

> eth.getBalance(personal.listAccounts[0]).toNumber()


Great we now have ethers. We can stop miner by specifying ‘miner.stop()’, to stop unnecessary mining. We can check the height of blockchain by running following command :

> web3.eth.getBlockNumber(function(e,r){ console.log(r)})


Which is telling us that current height of blockchain is 2. We can view any block by specifying it number by issuing following command :

> web3.eth.getBlock(1)


difficulty: 1903376,

extraData: "0xd88301080c846765746887676f312e392e328664617277696e",

gasLimit: 20979494,

gasUsed: 0,

hash: "0x6d719d3447497302f59aac284cbb7df585c4cc591c4d351d994d4c234c667ac7",

logsBloom: "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",

miner: "0x66c4c909098df782ef0a52464749de9ef294762c",

mixHash: "0x094731b8b22a8efba3327b61fe602d4e76e8857ff12db14c8d53afbd651260ff",

nonce: "0x082d1975e5cbe2c8",

number: 1,

parentHash: "0x07185fe5cd8ac52781a3893b7d08b1240c1ded9f84eb97ee68fe2901ed82bcc4",

receiptsRoot: "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421",

sha3Uncles: "0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347",

size: 537,

stateRoot: "0xa3c4d51416278ab6c77c407027870d9a2c5e214d40e7d32f0275d692ca5ca69f",

timestamp: 1529571309,

totalDifficulty: 3903376,

transactions: [],

transactionsRoot: "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421",

uncles: []


Amazing, now we have properly running Ethereum private network with development environment set up. We are ready to move on to next tutorial.