Files
bitcoin/doc
merge-script 32765aca5c Merge bitcoin/bitcoin#35730: http: limit connected HTTPRemoteClients
bd4b1524ea init: do not count file descriptors for HTTPServer if -server=0 (Matthew Zipkin)
b08662060d init: account for maximum file descriptors needed by HTTP (Matthew Zipkin)
cc2acebefb http: configure simultaneous connection limit with -rpcmaxconnections (Matthew Zipkin)
b3d6d2d1a7 http: limit connected clients to 16 (Matthew Zipkin)
86651d8197 scripted-diff: Rename nUserBind, nBind, nMaxConnections to snake_case (Matthew Zipkin)

Pull request description:

  Introduces a new configuration option `-rpcmaxconnections` with default value `16`. This is used to limit the number of simultaneous `HTTPClient` connected to the `HTTPServer`. When the limit is reached, new pending connections remain queued in the kernel's socket buffer. Those connections have complete TCP handshakes with the kernel but do not occupy any application memory.

  The previous libevent-based HTTP server had no limit on connections but it did have a limit on the kernel socket queue:

  e7ff4ef2b4/http.c (L3510)
  ```c
  if (listen(fd, 128) == -1) {
  ```

  The current HTTP server, like the p2p server, uses a platform constant here:

  b6becf3534/src/httpserver.cpp (L743)

  (on my macOS `SOMAXCONN` is `128` but on my Debian machine it's `4096`)

  The default of 16 was chosen as a reasonable upper bound for single-user RPC use cases. Systems designed to handle more simultaneous HTTP connections than this (previously relying on the absence of a limit) can adjust the setting.

  ## File descriptors

  Because of the connection limit, we can now account for the maximum number of file descriptors needed by the HTTP server. This addresses several issues (#11368 #11322 maybe #27732) that could have been fixed by a PR waiting in vain for a libevent release (#27731).

  ## Bonus performance improvement

  The new limit is managed in a loop that drains the kernel's socket queue with `accept()`. All pending connections from the queue (up to the limit) are processed in one single call to `SocketHandlerListening()`. The previous code would only accept one connection from the queue on each I/O loop tick, with a `SELECT_TIMEOUT` (50ms) sleep between each.

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Bitcoin Core

Setup

Bitcoin Core is the original Bitcoin client and it builds the backbone of the network. It downloads and, by default, stores the entire history of Bitcoin transactions, which requires several hundred gigabytes or more of disk space. Depending on the speed of your computer and network connection, the synchronization process can take anywhere from a few hours to several days or more.

To download Bitcoin Core, visit bitcoincore.org.

Running

The following are some helpful notes on how to run Bitcoin Core on your native platform.

Unix

Unpack the files into a directory and run:

  • bin/bitcoin-qt (GUI) or
  • bin/bitcoind (headless)
  • bin/bitcoin (wrapper command)

The bitcoin command supports subcommands like bitcoin gui, bitcoin node, and bitcoin rpc exposing different functionality. Subcommands can be listed with bitcoin help.

Windows

Unpack the files into a directory, and then run bitcoin-qt.exe.

macOS

Drag Bitcoin Core to your applications folder, and then run Bitcoin Core.

Need Help?

Building

The following are developer notes on how to build Bitcoin Core on your native platform. They are not complete guides, but include notes on the necessary libraries, compile flags, etc.

Development

The Bitcoin repo's root README contains relevant information on the development process and automated testing.

Resources

Miscellaneous

License

Distributed under the MIT software license.