Ethereum Private Blockchain – How to Track Transactions in Private Ethereum Blockchain

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I am bit confused by the value of "root" I get in transaction receipt

according to my understanding root is the value which points to previous block in block chian,

but when I try to track that block by the value of root it shows null or not found
I have tried following two ways

debug.traceBlockByHash("hash(value of root)")

AND

eth.getTransactionReceipt("hash(value of root)")

but cant track the root block

For reference:-
my transaction receipt

{
  blockHash: "0x38745b73aaca70ae40dd4f89e039dd4afb90cf606308701548200d8a757e69be",
  blockNumber: 10897,
  contractAddress: null,
  cumulativeGasUsed: 73966,
  from: "0xf0606aab9ed3f89a4167b43ce4eed4ff8f4cc195",
  gasUsed: 32855,
  logs: [],
  logsBloom: "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000",
  root: "0x25eba79d41fbe9d11c8a82a2b1629784e80e7c5322832f5386d13b5bd211c8e2",
  to: "0x742c8105ba6cfd99ff20ffc19332a9782caecb8a",
  transactionHash: "0xb3645970eecb8b2b1e00d2b2f4bff5bab90bbdcb36300ad44348a0e954073f22",
  transactionIndex: 1
}

following are the outputs I received

> debug.traceBlockByHash("0x25eba79d41fbe9d11c8a82a2b1629784e80e7c5322832f5386d13b5bd211c8e2")
{
  error: "block #25eba79d41fbe9d11c8a82a2b1629784e80e7c5322832f5386d13b5bd211c8e2 not found",
  structLogs: null,
  validated: false
}

AND

> eth.getTransactionReceipt("0x25eba79d41fbe9d11c8a82a2b1629784e80e7c5322832f5386d13b5bd211c8e2")
null

one more confusing thing is the block number which I see in transaction receipt are not consecutive for consecutive transactions,
ie. If my first transaction receipt has

Block Number: 10849

then the

next one is 10853

next is 10865

how this block number is generated??

Best Answer

You identify a block with either blockHash, which is the hash of the block, or blockNumber, which is the position of the block in the chain. Blocks can contain multiple transactions and are generated even if there are no transactions in them, so they should not be expected to increase in series with your transactions. blockNumber is sometimes referred to as "height". Watch the console or log output of a node if you want to see blocks getting generated.

You can get block information with eth.getBlock(). Pass it a block hash or block number.

You can get transaction information with eth.getTransaction(). Pass it the transaction hash of the transaction you are interested in.

eth.getTransactionReceipt() also expects a transaction hash.

You don't need root for any of the purposes you mention, but if you're curious what it is, see: What is the 'root' of a transaction receipt?

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Partial answer: it may be that you can't get a block number with

var block = web3.eth.getBlock(result, true);
alert(block.number);

because the block is "pending", in which case its number will be null (see web3.eth.getBlock return value description).

Solidity Hash – How to Get the Hash of Head Block in Private Chain?

Question 2: Why the number of blocks keeps increasing in a private chain even though no transaction is being sent to the chain?

If you carefully look at how a blockchain works, this is something important to assure the integrity of the blockchin data. Normally a blockchain protocol works in a way to keep the block rate constant, in order to make it difficult to create a another chain which is longer. In ethereum a block is generated nearly every 14 seconds, and the difficulty is what keeps the average blockrate at that rate. You may refer this answer.

So whether there are transactions or not, miner s keep mining blocks and that's how the protocol is defined for a public network and since you are using the same protocol in your private chain (default geth client), In your private chain also its the same. The code @StevenJaxon had linked can be used to alter your private chain but then it would not be simulating the public chain anyhow for testing purposes that won't matter and it will save your computing power as well.

Question 1: How to get the hash value head/current block in a private chain?

This pretty straight forward if you refer the web3 API reference here and here,

web3.eth.blockNumber // return current block number
web3.eth.getBlock(blockHashOrBlockNumber [, returnTransactionObjects] [, callback]) // returns a block given the hash or number

//combine both
currentBlock = web3.eth.blockNumber;
web3.eth.getBlock(currentBlock, function(block){
    //do whatever with the block details
});

If what you want to do this inside a smart contract, you only be able to get the previous block number, and you can use the following code, refer this question.

contract Test {
    uint public blockNumber;
    bytes32 public blockHashNow;
    bytes32 public blockHashPrevious;

    function setValues() {
        blockNumber = block.number;
        blockHashNow = block.blockhash(blockNumber);
        blockHashPrevious = block.blockhash(blockNumber - 1);
    }    
}

Best Answer

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Solidity Hash – How to Get the Hash of Head Block in Private Chain?

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