For a future network with bigger blocks.
Licence: MIT Language: Python (>= 3.5.3) Author: Neil Booth
See docs/HOWTO.rst.
- Efficient, lightweight reimplementation of electrum-server
- Fast synchronization of bitcoin mainnet from Genesis. Recent hardware should synchronize in well under 24 hours. The fastest time to height 448k (mid January 2017) reported is under 4h 30m. On the same hardware JElectrum would take around 4 days and electrum-server probably around 1 month.
- The full Electrum protocol is implemented. The only exception is the blockchain.address.get_proof RPC call, which is not used by Electrum GUI clients, and can only be invoked from the command line.
- Various configurable means of controlling resource consumption and handling denial of service attacks. These include maximum connection counts, subscription limits per-connection and across all connections, maximum response size, per-session bandwidth limits, and session timeouts.
- Minimal resource usage once caught up and serving clients; tracking the transaction mempool appears to be the most expensive part.
- Fully asynchronous processing of new blocks, mempool updates, and client requests. Busy clients should not noticeably impede other clients' requests and notifications, nor the processing of incoming blocks and mempool updates.
- Daemon failover. More than one daemon can be specified, and ElectrumX will failover round-robin style if the current one fails for any reason.
- Peer discovery protocol removes need for IRC
- Coin abstraction makes compatible altcoin and testnet support easy.
Mainly for privacy reasons, I have long wanted to run my own Electrum server, but I struggled to set it up or get it to work on my DragonFlyBSD system and lost interest for over a year.
In September 2016 I heard that electrum-server databases were getting large (35-45GB when gzipped), and it would take several weeks to sync from Genesis (and was sufficiently painful that no one seems to have done it for about a year). This made me curious about improvements and after taking a look at the code I decided to try a different approach.
I prefer Python3 over Python2, and the fact that Electrum is stuck on Python2 has been frustrating for a while. It's easier to change the server to Python3 than the client, so I decided to write my effort in Python3.
It also seemed like a good opportunity to learn about asyncio, a wonderful and powerful feature introduced in Python 3.4. Incidentally, asyncio would also make a much better way to implement the Electrum client.
Finally though no fan of most altcoins I wanted to write a codebase that could easily be reused for those alts that are reasonably compatible with Bitcoin. Such an abstraction is also useful for testnets.
ElectrumX does not do any pruning or throwing away of history. I want to retain this property for as long as it is feasible, and it appears efficiently achievable for the forseeable future with plain Python.
The following all play a part in making ElectrumX very efficient as a Python blockchain indexer:
- aggressive caching and batching of DB writes
- more compact and efficient representation of UTXOs, address index, and history. Electrum Server stores full transaction hash and height for each UTXO, and does the same in its pruned history. In contrast ElectrumX just stores the transaction number in the linear history of transactions. For at least another 5 years this transaction number will fit in a 4-byte integer, and when necessary expanding to 5 or 6 bytes is trivial. ElectrumX can determine block height from a simple binary search of tx counts stored on disk. ElectrumX stores historical transaction hashes in a linear array on disk.
- placing static append-only metadata indexable by position on disk rather than in levelDB. It would be nice to do this for histories but I cannot think of a way.
- avoiding unnecessary or redundant computations, such as converting address hashes to human-readable ASCII strings with expensive bignum arithmetic, and then back again.
- better choice of Python data structures giving lower memory usage as well as faster traversal
- leveraging asyncio for asynchronous prefetch of blocks to mostly eliminate CPU idling. As a Python program ElectrumX is unavoidably single-threaded in its essence; we must keep that CPU core busy.
Python's asyncio means ElectrumX has no (direct) use for threads
and associated complications.
- Python 3.6, which has several performance improvements relevant to ElectrumX
- UTXO root logic and implementation
- incremental history serving / pruning
- new features such as possibly adding label server functionality
- potentially move some functionality to C or C++
Minor peer-discovery tweaks:
- I intended that if a host and its IP address were both registered as peers, that the real hostname replace the IP address. That wasn't working properly and is fixed now.
- 1.0.6 no longer required a clearnet identity but part of the peer discovery logic assumed one existed. That is now fixed.
Improvements to proxy handling and peer discovery
- background async proxy detection loop. Removes responsibility for proxy detection and maintenance from the peer manager.
- peer discovery waits for an initial proxy detection attempt to complete before starting
- new feature: flag to force peer discovery to happen via the proxy. This might be useful for someone exlusively running a Tor service that doesn't want to reveal its IP address. See FORCE_PROXY in docs/ENVIRONMENT.rst for details and caveats.
- other minor fixes and tweaks
- updated to handle incompatibilities between aiohttp 1.0 and 2.0. ElexctrumX should work with either for now; I will drop support for 1.0 in a few months. Fixes #163.
- relax get_chunk restrictions for clients 1.8.3 and higher. Closes #162.
- REPORT_HOST no longer defaults to HOST. If not set, no clearnet identity will be advertised.
- Add Viacoin support (romanornr)
- the peer looping was actually just looping of logging output, not connections. Hopefully fixed for good in this release. Closes #160.
- fix another unwanted loop in peer discovery, tweak diagnostics
- fix a verification loop that happened occasionally with bad peers
- stricter acceptance of add_peer requests: rate-limit onion peers, and require incoming requests to resolve to the requesting IP address
- validate peer hostnames (closes #157)
- verify height for all peers (closes #152)
- various improvements to peer handling
- various documentation tweaks
- limit the maximum number of sessions based on the process's open file soft limit (closes #158)
- improved altcoin support for variable-length block headers and AuxPoW (erasmospunk) (closes #128 and #83)
- Rate-limit add_peer calls in a random way
- Fix discovery of base height in reorgs
- Don't permit common but invalid REPORT_HOST values
- Set reorg limit to 8000 blocks on testnet
- dogecoin / litecoin parameter fixes (erasmospunk, pooler)
- minor doc tweaks
- Minor doc tweaks only
- Add support for Bitcoin Unlimited's nolnet; set NET to nolnet
- Choose 2 peers per bucket
- Minor bugfix
- Require Python 3.5.3. 3.5.2 has asyncio API and socket-related issues. Resolves #135
- Remove peer semaphore
- Improved Base58 handling for >1 byte version prefix (erasmospunk)
- don't announce self if a non-public IP address
- logging tweaks
- Add more verbose logging in attempt to understand issue #135
- REPORT_TCP_PORT_TOR and REPORT_SSL_PORT_TOR were ignored when constructing IRC real names. Fixes #136
- Only serve chunk requests in forward direction; disconnect clients iterating backwards. Minimizes bandwidth consumption caused by misbehaving Electrum clients. Closes #132
- Tor coin peers would always be scheduled for check, fixes #138 (fr3aker)
Preparation for release of 1.0, which will only have bug fixes and documentation updates.
- improve handling of daemon going down so that incoming connections are not blocked. Also improve logging thereof. Fixes #100.
- add facility to disable peer discovery and/or self announcement, see docs/ENVIRONMENT.rst.
- add FairCoin (thokon00)
Neil Booth [email protected] https://github.com/kyuupichan
1BWwXJH3q6PRsizBkSGm2Uw4Sz1urZ5sCj