Questions tagged [mempool]

Every node has their unique memory pool in which it tracks unconfirmed transactions. Use this tag for questions on how transactions enter and exit the mempool, how the mempool is delimited and other aspects of how it works.

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Reorgs and MEV in Bitcoin

Recently one of the altcoin that has lot of other issues is in news because of MEV (Miner Extractable Value). Honestly I don't care if someone exploits it or it affects the altcoin in any other way. ...
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Making regtest's generatetoaddress work with blocksonly=1

I'm setting up a regtest scenario in which I want to send transactions which should be included in new blocks created via the generatetoaddress RPC call. However, I want to disable transaction ...
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Can I transfer some BTC with 0 tx fee now, when the mempool is empty?

I wanna send a tiny amount of BTC (0.001BTC). I am not in a hurry and I noticed the mempool is sometimes empty these days because the market is cold. So can I set the network fee to 1sat/byte or even ...
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308 views

What happens if nSequence is set to 0x00000000?

I know setting nSequence 0x00000001 means the transaction is not valid until 1 block has elapsed since its's prevout confirms. At most one spend per two blocks. What happens if it's set to 0x00000000? ...
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A question about CPFP relaying policy

Let's say I broadcast a transaction tx0 signaling RBF replaceability. Later on, send another transaction tx1 that spends the same inputs of tx0, but this time with higher fees. In this case, tx0 is ...
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36 views

what happens to low-fee or forgotten transactions

If a transaction has a fee that is too low then it is possible for the transaction to either age out of the mempool (14 days) or get removed because the mempool reaches its max size. So what happens ...
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56 views

How to save the mempool information immediately before the node receives a block?

I want to use Bitcoin RPC API 'getrawmempool' to save the snapshot of the mempool immediately before my full node receives a block. This requires modification of the Bitcoin source code. How should I ...
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Sent transaction on 30 march 2021 still unconfirmed in mempool what can i do? [duplicate]

I made small BTC transaction from my bitcoincore wallet to account of Binance on March 30, 2021. I did set the fee low. But i wait a month for the transaction to back to my wallet. But it said still ...
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59 views

How are txns sorted correctly in Merkle trees between nodes and validated via Proof of Work

I am interested in exactly what happens to transactions in the pending block (block that is being mined at the time). From what I understand, transactions are the stored as a Merkle tree hash inside ...
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592 views

Why does the mined block differ so much from the block template?

I am looking at the specific block at height 680175. At the time when the block was not mined yet, I received the block template via bitcoin-cli getblocktemplate '{"rules": ["segwit&...
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TX Validation: Can a miner choose specific tx to validate from mempool? [duplicate]

I have made two TXs few days back and they remain unconfirmed so far. Can I be a bitcoin miner and validate them myself? And what happens if it remains as it is? There are some big amount of utxo ...
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42 views

Miner's pool and Mempool relationship

I am wondering why we need Mempool (central and aggregated pool) while each miner has its own pool? If we need the Mempool as an architectural design, how we can make sure that miners are sending ...
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How can an output be spent while the transaction is in mempool

I have seen transactions on a block explorer where the transaction is in mempool (unconfirmed) but one of the outputs already appears as spent, I am curious how this works. This question is a ...
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28 views

What is the difference between the txsize in mempool and mempool dynamic usage?

There is a table for the txsize in mempool and dynamic memory usage of mempool on statoshi.info's mempool overview? The default size of mempool defined in Bitcoin is 300MB, so is this default size the ...
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Where can I get a list of stale RBF'd transactions?

I would like to prove that a certain transaction was in the mempool on a certain date before it got replaced via RBF with another transaction. Is there any service that provides this data?
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125 views

Trying to understand the mempool and how transactions are picked

I am very new to blockchain and try to understand it completely. What I think I understood is, that every transaction is going to the mempool first and these transactions are getting picked by miners. ...
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Bitcoin Transactions confirmation [duplicate]

I'm new to crypto trading and id like to know if bitcoin transactions have ever taken more than 7 days to confirm? kind regards rob
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80 views

Does my node rebroadcast its mempool transactions on startup?

Say my node has transactions in its mempool and then gets shut down and restarted. Does it save the mempool to disk and reload this mempool when it starts back up, or does its mempool get lost on ...
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195 views

Will nodes configured with a larger-than-default mempool automatically retransmit transactions that have been dropped from the default mempool?

If a transaction is sent and dropped from the default mempool before it is included in a block, but nodes with a larger-than-default mempool size exist that still have the transaction, will those ...
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60 views

Sending less than 0.001 BTC from my Bitcoin Core Wallet not in memory pool

I recently managed to recover my wallet.dat and passphrase and have been trying to send the 0.00126913 BTC balance from my Bitcoin Core wallet into my Binance account, however the transactions stay ...
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107 views

Bitcoin transaction failed to broadcast (code 66)

I am using bitcoind. I got this error while trying to send a transaction: CommitTransaction(): Transaction cannot be broadcast immediately, mempool min fee not met, 6835 < 7865 (code 66) The ...
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What unconfirmed transactions in Mempool get into a block? [duplicate]

I have a question regarding picking unconfirmed transactions from the mempool. Let's say, there are 1000 transactions in the mempool. Can I randomly select some transactions, say, transaction a, b, c, ...
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85 views

Where in ~/.bitcoin are mempool and UTXO pools written?

Where in ~/.bitcoin are the two pools in question stored when their size grows above the size set by dbcache and maxmempool in bitcoin.conf. Is UTXO pool written to such location at Bitcoin Core's ...
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52 views

Do miners mine their own transactions or submit them to the network?

I am wondering how miners are behaving toward their own transactions. Do they send their own transactions to the mempool or can they process/confirm them directly? I am assuming that the miners are ...
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98 views

How to choose the transactions for a block?

From my understanding, the memory pool (or transaction pool) contains "open" or "unconfirmed" transactions that have to be validated and can be chosen (arbitrarily?) to be part of ...
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309 views

Unconfirmed transaction for 6 days now. need assistance for using CPFP

I have an unconfirmed transaction that has been sitting there for 6 days now. The fees only got higher sins i've made the transaction and i do not feel comfortabel waiting. I'm unable to use RBF sins ...
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37 views

Why are the drops in mempool unconfirmed transaction count not of constant height?

I was just browsing the following mempool visualization and couldn't come up with a good explanation why the drops in unconfirmed transaction count are not of pretty much constant height but vary ...
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343 views

What is the network mempools unconfirmed transaction expiration time?

I sent a bare $1000 multisig transaction using sendrawtransaction with a too low fee. When I create a new transaction with a higher fee, I m getting txn-mempool-conflict error, and when I use the ...
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228 views

Why can't default minimum fee rate be changed to 0.1-0.2 sat/vByte?

Main question (focus on this incase you are looking to close it as "needs focus"): Why can't we change default minimum fee rate to something below 1 sat/vByte? It was done in past: https://...
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48 views

Which tool can I use to calculate the best fee for a specific time?

Let's say I'm okay with a transaction to be included in a block in about 24h. The fee is obviously dependent on the network congestion. Which (online) tools can I use to calculate the optimal fee ...
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93 views

Where can I find a survey on different fee estimation algorithms?

I am looking for a comparison or summary of different fee estimation algorithms. Does anyone know of one? I would like to see what the best starting point is in order to see where optimization can be ...
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42 views

Better fee estimation and fee/tx/mempool management in wallets

Right now mempool has 65 MB of transactions waiting for miners to be included in blocks. 90% of the transactions are below 10 sat/vbyte. I am observing this trend from last few days and think it will ...
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168 views

Change -mempoolexpiry in BitcoinCore 0.20.1

I have accidentally made a transaction with a very low fee (5 sat/byte) and I doubt that it will be confirmed any time soon. Replace-By-Fee is not available since my transaction has no change. Abandon ...
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how to get txid with sha256

I am trying to get a txId from a transaction without any bitcoin libraries. I can use low level libries though such as crypto, sha256 and so on. I have a class which contains version, vins, vouts, ...
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290 views

Transaction being ignored by miners, I mean Ignored, Not “not mined because low fees”

I'm working on a project to visualize the mempool and (also) check if a transaction is being ignored by miners. I have my own mining queue, to compare "my first block" with the block that ...
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717 views

Can you explain some of the dynamics that drive the variations in mempool depth?

I often see mempool graphs such as Jochen Hoenicke's that show significant fluctuations in mempool depth and hence the fee needed to get into upcoming blocks. Can you explain some of the dynamics that ...
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108 views

DumpMempool() and LoadMempool() in src/validation.cpp

My understanding is that DumpMempool() saves the memory pool state (unconfirmed txs received from other peers and if any txs broadcasted from this node) to disk and LoadMempool() is used if this state ...
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93 views

How do I get new unconfirmed transaction from mempool?

I know there is a function that allows me to see all transactions that are in mempool, but is there a way to see every new transaction that enters mempool? Like log to file whenever new unconfirmed ...
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534 views

Clarifying descendants/ancestors in error cases for too-long-mempool-chain

In practice I've seen two instances of the too-long-mempool-chain error when trying to send a transaction: When there are too many unconfirmed transactions chained together: "too many descendants ...
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Does the mempool size as reported by Blockchain.com include the size of txs only?

Does the mempool size as reported by (for instance Blockchain.com) include the sum of the 'size' of transactions only? Or does it also include the overhead (due to indexes, allocation overhead, ...
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Why are the fee value and modified fee value always the same?

I do not see any transaction in the mempool having differing values for the fee and modified fee fields. Does nobody modify or accelerate their transactions? How do transactions with modified fees ...
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79 views

How to recognize dependent transactions sitting in the mempool?

I am trying to find out the relation among dependent transactions in the mempool. I have already used the "depends" field and tracked the transaction ids to go through. But I still can not ...
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70 views

Does testmempoolaccept check all possible rejection rules?

Is there any rejection rule that testmempoolaccept will not check, or is it safe to assume that if it passes testmempoolaccept validation it will be at least broadcast? Mostly concerned about complex ...
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My unconfirmed BTC transaction on blockchain just disappeared [duplicate]

I had an unconfirmed BTC transaction on blockchain.com for about 2 days plus and now I log in and there's no transaction again. I checked blockchain.info using the hash; all wiped nothing is showing, ...
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49 views

What valid transactions are not broadcastable?

Many valid transactions are not broadcastable by default in bitcoin core to avoid attacks that could harm the network. These would rarely be found in a node's mempool but could, however, be found in ...
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56 views

How to accelerate mempool data access with bitcoind

What could I do to accelerate access to the data I get when I call for example: bitcoin-cli getblocktemplate ? If I would like to be able to be the fisrt one who get information about all the new tx ...
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1answer
200 views

Segfault when clearing mempool. What am I doing wrong?

Background: For a research project, I am trying to periodically clear the content of my Bitcoin node's mempool. For this purpose I have created a new thread in init.cpp using the boost threadgroup (I ...
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2answers
93 views

What is the default number of transactions a full node have in its mempool?

Is there a default limit to the number of transactions a node can keep in its memory pool? Or do we have to explicitly declare maxmempool=xyz to restrict the number of transactions a node can have in ...
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What happens to transactions in the mempool when their parent transaction expires?

I was just reading the Coin Metrics Newsletter #53, and it included a section about the recent mempool congestion. After mentioning transactions that got evicted due to the network's queue of ...
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What if two people want to spend same input at the same time

Lets say me and my friend both have access to same private key which can sign some new transaction. What would happen if me and my friend broadcast transaction with same input at the same time to a ...