P2Pool

Visualization of the P2Pool share chain

P2Pool is a decentralized Bitcoin mining pool that works by creating a peer-to-peer network of miner nodes.

P2Pool creates a new block chain in which the difficulty is adjusted so a new block is found every 10 seconds. The blocks that get into the P2Pool block chain (called the "share chain") are the same blocks that would get into the Bitcoin block chain, only they have a lower difficulty target. Whenever a peer announces a new share found (new block in the P2Pool block chain), it is received by the other peers, and the other peers verify that this block contains payouts for all the previous miners who found a share (and announced it) that made it into the P2Pool share chain. This continues until some peer finds a block that has a difficulty that meets the Bitcoin network's difficulty target. This peer announces this block to the Bitcoin network and miners who have submitted shares for this block are paid in the generation transaction, proportionally to how many shares they have found in the last while. - Unknown author

Decentralized payout pooling solves the problem of centralized mining pools degrading the decentralization of Bitcoin, avoids the risk of hard to detect theft by pool operators, and has better fundamental resistance to DoS attacks than centralized pools.

Miners are configured to connect to a P2Pool node that can be run locally, alongside the miner. P2Pool users must run a full Bitcoin node which serves the purpose of independently validating transactions and the Bitcoin blockchain. P2Pool also supports merged mining and several alternative blockchains.

P2Pool nodes work on a chain of shares similar to Bitcoin's blockchain. Each node works on a block that includes payouts to the previous shares' owners and the node itself, which can also result in a share if it meets P2Pool's difficulty.

Because of the importance of strengthening Bitcoin's decentralization some Bitcoin supporters donate to P2Pool miners, resulting in returns above 100% of the expected reward.

Overview

P2Pool shares form a "sharechain" with each share referencing the previous share's hash. Each share contains a standard Bitcoin block header, some P2Pool-specific data that is used to compute the generation transaction (total subsidy, payout script of this share, a nonce, the previous share's hash, and the current target for shares), and a Merkle branch linking that generation transaction to the block header's Merkle hash.

The chain continuously regulates its target to keep generation around one share every ten seconds, just as Bitcoin regulates it to generate one block every ten minutes.

Unlike Bitcoin, nodes do not know the entire chain - instead they only hold the last 8640 shares (the last day's worth). In order to prevent an attacker from working on a chain in secret and then releasing it, overriding the existing chain, chains are judged by how much work they have since a point in the past. To ascertain that the work has been done since that point, nodes look at the Bitcoin blocks that the shares reference, establishing a provable timestamp. (If a share points to a block, it was definitely made after that block was made.)

Payout logic

Each share contains a generation transaction that pays to the previous n shares, where n is the number of shares whose total work is equal to 3 times the average work required to solve a block, or 8640, whichever is smaller. Payouts are weighted based on the amount of work each share took to solve, which is proportional to the p2pool difficulty at that time.

The block reward (currently 50BTC) and the transaction fees are combined and apportioned according to these rules:

A subsidy of 0.5% is sent to the node that solved the block in order to discourage not sharing solutions that qualify as a block. (A miner with the aim to harm others could withhold the block, thereby preventing anybody from getting paid. He can NOT redirect the payout to himself.) The remaining 99.5% is distributed evenly to miners based on work done recently.

In the event that a share qualifies as a block, this generation transaction is exposed to the Bitcoin network and takes effect, transferring each node its payout.

Stales

P2Pool stales don't work the same way as stales on centralized pools. On a centralized pool a stale is work which is too old to be accepted by the pool's Bitcoin node; this kind of stale is very rare in P2Pool because each user runs their own local bitcoind.

On P2Pool stales refer to shares which can't make it into the sharechain. Because the sharechain is 60 times faster than the Bitcoin chain many stales are common and expected. However, because the payout is PPLNS only your stale rate relative to other nodes is relevant; the absolute rate is not.

There are two reported kinds of stales in P2Pool: "DEAD ON ARRIVAL" shares and orphan shares. Dead shares were too old by the time they arrived at your local P2Pool. Very high dead rates can indicate miner misconfiguration. Orphan shares are shares which were not extended by the rest of the P2Pool network, because some other miner's share was accepted first. Very high orphan rates may indicate network connectivity problems.

The P2Pool console output shows your relative stale rate compared to other P2Pool miners in the 'Own efficiency' column:

2012-01-07 20:57:51.797420 Pool stales: 13% Own: 13±2% Own efficiency: 100±2%

When you first start P2Pool claimed efficiency will be low and the error bounds on this estimate will be large, but as it runs the numbers will converge to their correct values.

If your efficiency is unusually low, make sure your network connection isn't overloaded, that your miners support long polling and are not set to work for excessive amounts of time, and that your bitcoind has multiple connections.

Joining the pool

Follow these steps to join the pool:

• Run Bitcoin with the RPC interface enabled: put rpcuser=USER, rpcpassword=LONG_RANDOM_SECRET_VALUE, and server=1 in bitcoin.conf (on separate lines)
  • Replace LONG_RANDOM_SECRET_VALUE with something long and random like the output of smashing your keyboard for a bit like fju4M78yAj3ds39pak92raK. You don't need to be able to remember it. If your RPC port becomes exposed to the internet a thief could steal your bitcoin if they could guess it, or use a brute force attack in order to find it.
  • Bitcoin 0.5 or later is required
  • It's important that your Bitcoin client be fully synchronized before starting. It's also better if you have the Bitcoin port forwarded
• Download p2pool:
  • Windows binary: See http://forum.bitcoin.org/index.php?topic=18313.0
  • Source download: https://github.com/forrestv/p2pool/tags
  • git: git clone git://github.com/forrestv/p2pool.git
• Run p2pool: (See below for additional options.)
  • Windows py2exe: run_p2pool.exe
  • Source: python run_p2pool.py
• Run a miner daemon with long polling connecting to 127.0.0.1 (or the IP of the host running p2pool if it isn't on the same computer as the miner) on port 9332 with any username and password
  • cgminer -O u:p -o http://127.0.0.1:9332/ --submit-stales

Dependencies if running from source:

• Python 2.6 or higher
• python-argparse for Python 2.6 and lower
• Twisted (Ubuntu package python-twisted)

Frequently Asked Questions

Q: "Why does cgminer report so many longpoll events when mining on p2pool? - P4Man"
A: "Once every ~10 seconds is normal. That is how often p2pool shares are generated (as opposed to ~10 min for bitcoin blocks) - cabin"

Q: "Do the 'orphan' and 'dead' shares in P2Pool's status display hurt me?"
A: They shouldn't - It's normal for some fraction of everyone's shares to end up orphaned or dead. Because payouts are calculated by counting how many shares you have relative to others, everyone with normal configurations is equally "hurt" by this. However, if you have a large proportion of stales, your payout will be hurt. You can see how well you're doing by looking at P2Pool's "Efficiency" (ex: Efficiency: ~110.6% (40-111%)). If 100% doesn't lie within the confidence interval at the end, something is probably wrong (with 95% confidence).

Q: "What do I do if my efficiency is low?"
A: Make sure the computers you're running P2Pool and the miner on have enough memory and CPU time. If you have a lot of dead shares or the "Local dead on arrival" number is higher than a few percent, that means that something is wrong with your miner. Check to make sure that it is one of the working versions in the Miners section on this page. Lower the intensity or raise the FPS of your miner. If you have a lot of orphan shares, something is wrong with P2Pool's P2P connection. Decrease the load on your internet connection or enable QoS (Quality of Service) on your router.

Q: What is PPLNS?
A: Pay-Per-Last-N-Shares is a payout method that is completely resistant to pool hoppers.

Q: Why am I not getting very many shares?!
A: The P2Pool difficulty is hundreds of times higher than on normal pools. It can take time to get a share. P2Pool displays an estimate of how long you have to wait in the console output.

Q: Why does my miner say it has found a lot of shares but p2pool say I have only found a few?!
A: The real P2Pool difficulty is hundreds of times higher than on normal pools, but p2pool essentially lies to your miner and tells it to work on relatively easy shares so that it submits shares every few seconds instead of every few hours. P2Pool then ignores any submitted shares that don't match the real share difficulty. By doing this, P2Pool can more accurately report your local hash rate and you can see if you are having problems with too many stale shares quickly

Q: Why am I getting so many rejects?
A: You're using an incompatible miner. See the miners section here, increase your FPS on the miner, decrease the intensity, upgrade your miner, or try a different miner.

Q: What stops the pool operator or the block finder from stealing a block?
A: A block solution is only worth anything because its hash matches Bitcoin's target. Altering anything within the block will change its hash and make it worthless.

Q: Why does it say "Generated?" I want to spend my coins now!
A: P2Pool includes payouts in generation transactions, which must mature (taking 120 blocks or 20 hours) before they can be spent. The reason for this is that a block could be orphaned, which would make its payout invalid and could reverse transactions.

Q: Do I get paid transaction fees?
A: Yes. They are split among P2Pool miners.

Q: What are these payments I'm getting that aren't generated?
A: These are subsidies that people who support the idea of P2Pool send to miners.

Q: Cool Subsidies sound like an awesome idea! How do I send some BTC to these awesome miners?
A: See end of this page.

Q: Do I really need the WHOLE blockchain?
A: Yes. Your node needs to be able to independently make decisions about what transactions to mine.

Q: How do merged mining payments work?
A: Merged mining is handled entirely by namecoind, so you're solo mining and payouts will go into namecoind's wallet.

Miners

This is all for the latest p2pool version, as it includes several new workarounds.

With all miners, using a HIGH FPS target (100?) or a LOW intensity (8 for cgminer?) helps a lot with reducing stales.

• cgminer works perfectly without any extra options. However, using multiple pools might cause problems, because long polling is only done for one pool.
• ufasoft works perfectly.
• DiabloMiner works fine after commit 3b731b9.
• Phoenix works fine after commit a658ef2.
• Poclbm works fine after commit 5e994e7.

P2Pool uses higher difficulty shares than most centralized pools, so you'll see fewer shares reported. This is normal and doesn't reduce your payments. It's also normal to see longpoll messages once per every ten seconds on average.

Useful features

• If upgrading P2Pool or changing its configuration, you can start another instance of P2Pool in parallel with the first. It will start normally, but realize that the worker and P2P listening ports are busy and keep trying to bind to them in the background. Thus, you can do almost-completely-seemless upgrades of P2Pool.
• If you run multiple P2Pool nodes or have trusted friends that run P2Pool, you can use -n to establish a constant extra P2P connection to them.
• You can make P2Pool use a configuration file by running run_p2pool.py @FILENAME, with FILENAME being the path to a file containing the command-line arguments (newlines are ignored) Example:

--net litecoin
-n 1.2.3.4

• Setting the username of your miner connecting to P2Pool to a Bitcoin address will make it mine to that address instead of the one requested from bitcoind or set by -a

Web interface

Lots of data and useful tools are available at http://127.0.0.1:9332/something:

• /graphs - RRD graphs of past hash rates for pool and local miners. Look for "VIP password" in P2Pool's output when it starts and use that for your miners to get graphs for individual miners.
• /rate
• /users
• /fee
• /current_payouts
• /patron_sendmany - Gives sendmany outputs for fair donations to P2Pool
• /global_stats
• /local_stats
• /peer_addresses
• /payout_addr
• /recent_blocks
• /uptime
• /chain_img - Visualization of sharechain
• /web/log - Some different stats collected over the last day

Included README

Requirements:
    Generic:
        Bitcoin >=0.5.0 or Litecoin
        Python
        Twisted
        python-argparse (for Python <=2.6)
    
    Linux:
        sudo apt-get install python-zope.interface python-twisted python-twisted-web
        sudo apt-get install python-argparse # if on Python 2.6 or older
    
    Windows:
        Install Python 2.7: http://www.python.org/getit/
        Install Twisted: http://twistedmatrix.com/trac/wiki/Downloads
        Install Zope.Interface: http://pypi.python.org/pypi/zope.interface/3.8.0
            Unzip the files into C:\Python27\Lib\site-packages

Running P2Pool:
    To use P2Pool, you must be running your own local bitcoind. For standard
    configurations, using P2Pool should be as simple as:

        python run_p2pool.py

    Then run your miner program, connecting to 127.0.0.1 on port 9332 with any
    username and password.

    If you are behind a NAT, you should enable TCP port forwarding on your
    router. Forward port 9333 to the host running P2Pool.

    Run "python run_p2pool.py --help" for additional options.

Notes for Litecoin:
    Requirements:
        In order to run P2Pool with the Litecoin network, you would need to build and install the
        ltc_scrypt module that includes the scrypt proof of work code that Litecoin uses for hashes.

        Linux:
            cd litecoin_scrypt
            sudo python setup.py install

        Windows:
            Install MinGW: http://www.mingw.org/wiki/Getting_Started
            Install Python 2.7: http://www.python.org/getit/

            cd litecoin_scrypt
            C:\Python27\python.exe setup.py build --compile=mingw32 install

            If you run into an error with unrecognized command line option '-mno-cygwin', see this:
                http://stackoverflow.com/questions/6034390/compiling-with-cython-and-mingw-produces-gcc-error-unrecognized-command-line-o
    
    Running P2Pool:
        Run P2Pool with the "--net litecoin" option.
        Run your miner program, connecting to 127.0.0.1 on port 9327.
        Forward port 9338 to the host running P2Pool.
        
        Litecoin's use of ports 9332 and 9332 conflicts with P2Pool running on
        the Bitcoin network. To avoid problems, add these lines to litecoin.conf
        and restart litecoind:
            rpcport=10332
            port=10333

Option Reference

usage: run_p2pool.py [-h] [--version] [--net {bitcoin, litecoin}] [--testnet]
                     [--debug] [-a ADDRESS] [--datadir DATADIR]
                     [--logfile LOGFILE] [--merged MERGED_URLS]
                     [--merged-url MERGED_URL]
                     [--merged-userpass MERGED_USERPASS]
                     [--give-author DONATION_PERCENTAGE] [--irc-announce]
                     [--p2pool-port PORT] [-n ADDR[:PORT]] [--disable-upnp]
                     [-w PORT] [-f FEE_PERCENTAGE]
                     [--bitcoind-address BITCOIND_ADDRESS]
                     [--bitcoind-rpc-port BITCOIND_RPC_PORT]
                     [--bitcoind-p2p-port BITCOIND_P2P_PORT]
                     [BITCOIND_RPCUSERPASS [BITCOIND_RPCUSERPASS ...]]

p2pool (version 28a1948)

optional arguments:
  -h, --help            show this help message and exit
  --version             show program's version number and exit
  --net {bitcoin, litecoin}
                        use specified network (default: bitcoin)
  --testnet             use the network's testnet
  --debug               enable debugging mode
  -a ADDRESS, --address ADDRESS
                        generate payouts to this address (default: <address
                        requested from bitcoind>)
  --datadir DATADIR     store data in this directory (default: <directory
                        run_p2pool.py is in>/data)
  --logfile LOGFILE     log to this file (default: data/<NET>/log)
  --merged MERGED_URLS  call getauxblock on this url to get work for merged
                        mining (example:
                        http://ncuser:ncpass@127.0.0.1:10332/)
  --merged-url MERGED_URL
                        DEPRECATED, use --merged
  --merged-userpass MERGED_USERPASS
                        DEPRECATED, use --merged
  --give-author DONATION_PERCENTAGE
                        donate this percentage of work to author of p2pool
                        (default: 0.5)
  --irc-announce        announce any blocks found on
                        irc://irc.freenode.net/#p2pool
  --disable-upnp        don't attempt to use UPnP to forward p2pool's P2P port
                        from the Internet to this computer

p2pool interface:
  --p2pool-port PORT    use port PORT to listen for connections (forward this
                        port from your router!) (default: bitcoin:9333,
                        litecoin:9338)
  -n ADDR[:PORT], --p2pool-node ADDR[:PORT]
                        connect to existing p2pool node at ADDR listening on
                        port PORT (defaults to default p2pool P2P port) in
                        addition to builtin addresses

worker interface:
  -w PORT, --worker-port PORT
                        listen on PORT for RPC connections from miners
                        (default: bitcoin:9332, litecoin:9327)
  -f FEE_PERCENTAGE, --fee FEE_PERCENTAGE
                        charge workers mining to their own bitcoin address (by
                        setting their miner's username to a bitcoin address)
                        this percentage fee to mine on your p2pool instance.
                        Amount displayed at http://127.0.0.1:WORKER_PORT/fee
                        (default: 0)

bitcoind interface:
  --bitcoind-address BITCOIND_ADDRESS
                        connect to this address (default: 127.0.0.1)
  --bitcoind-rpc-port BITCOIND_RPC_PORT
                        connect to JSON-RPC interface at this port (default:
                        bitcoin:8332, litecoin:9332 <read from bitcoin.conf if
                        password not provided>)
  --bitcoind-p2p-port BITCOIND_P2P_PORT
                        connect to P2P interface at this port (default:
                        bitcoin:8333, litecoin:9333 <read from bitcoin.conf if
                        password not provided>)
  BITCOIND_RPCUSERPASS  bitcoind RPC interface username, then password, space-
                        separated (only one being provided will cause the
                        username to default to being empty, and none will
                        cause P2Pool to read them from bitcoin.conf)

Protocol description

P2Pool's protocol mirrors Bitcoin's P2P protocol in many ways. It uses the same framing (prefix, command, length, checksum, payload) and similar commands:

• version - sent to establish a connection - contains (version, services, addr_to, addr_from, nonce, sub_version, mode, best_share_hash)
• setmode - sent to update the mode sent in the version message - contains (mode)
• ping - sent to keep connection alive - contains ()
• addrme - request that the receiving node send out an addr for the sending node - contains (port)
• addrs - broadcast list of nodes' addresses - contains (addrs)
• getaddrs - request that the receiving node send count addrs - contains (count)
• getshares - request that the receiving node send the shares referenced by hashes and parents of their parents, stopping at any share referenced by stops - contains (hashes, parents, stops)
• shares - broadcast message of the contents of shares - contains (shares)

History

This project was announced on June 17, 2011 by Forrest Voight.

The began testing against mainnet in mid-July, 2011. The pool was reviewed on a Bitcoin Miner post on July 26, 2011.

The software author's address for donations can be found in the signature section of his forum profile.

Donating to P2Pool miners

In order to encourage people to mine to P2Pool you can donate to the recent miners in proportion using a sendmany:

For example, a bash script to donate 10 btc is:

~/src/bitcoin/src/bitcoind sendmany "" "$(GET http://forre.st:9332/patron_sendmany?total=10)"

You can replace "" with "accountname" if you want to pay from some specific bitcoind account, and you can replace forre.st with 127.0.0.1 if you're running a P2Pool node locally, so you don't have to trust that the URL gives accurate figures.

Note that the amount you donate will be allocated to recent miners in proportion to the amount of work they've done in the last 24 hours or so, but all the miner whose shares of the donated amount are less than 0.01 BTC will have their shares combined into a single amount which is awarded to one of them at random, with the chance of winning this 'lottery' weighted by the miner's recent amount of work done. You can change this 0.01 BTC threshold like this, for example, which says to pay 10 BTC, but to share it amongst more miners that the default, cutting off at 0.001 BTC instead of at 0.01 BTC.

~/src/bitcoin/src/bitcoind sendmany "" "$(GET http://forre.st:9332/patron_sendmany?total=10/0.001)"

If you decide to donate you should announce it on the forums so that your donations provide the most incentive possible.

See Also

• Comparison of mining pools
• Pooled Mining

External Links

• P2Pool forum
• p2pool project on GitHub
• IRC Web #p2pool discussion and support
• p2pool.info stats page