This document describes usage of the multiprocess feature. For design information, see the design/multiprocess.md file.
On unix systems, the --enable-multiprocess build option can be passed to ./configure to build new dash-node, dash-wallet, and dash-gui executables alongside existing dashd and dash-qt executables.
The -debug=ipc command line option can be used to see requests and responses between processes.
The multiprocess feature requires Cap'n Proto and libmultiprocess as dependencies. A simple way to get started using it without installing these dependencies manually is to use the depends system with the MULTIPROCESS=1 dependency option passed to make:
cd <DASH_SOURCE_DIRECTORY>
make -C depends NO_QT=1 MULTIPROCESS=1
CONFIG_SITE=$PWD/depends/x86_64-pc-linux-gnu/share/config.site ./configure
make
src/dash-node -regtest -printtoconsole -debug=ipc
DASHD=dash-node test/functional/test_runner.py
The configure script will pick up settings and library locations from the depends directory, so there is no need to pass --enable-multiprocess as a separate flag when using the depends system (it's controlled by the MULTIPROCESS=1 option).
Alternately, you can install Cap'n Proto and libmultiprocess packages on your system, and just run ./configure --enable-multiprocess without using the depends system. The configure script will be able to locate the installed packages via pkg-config. See Installation section of the libmultiprocess readme for install steps. See build-unix.md and build-osx.md for information about installing dependencies in general.
dash-node is a drop-in replacement for dashd, and dash-gui is a drop-in replacement for dash-qt, and there are no differences in use or external behavior between the new and old executables. But internally after backporting bitcoin#10102, dash-gui will spawn a dash-node process to run P2P and RPC code, communicating with it across a socket pair, and dash-node will spawn dash-wallet to run wallet code, also communicating over a socket pair. This will let node, wallet, and GUI code run in separate address spaces for better isolation, and allow future improvements like being able to start and stop components independently on different machines and environments.
bitcoin#19460 also adds a new dash-node -ipcbind option and a dash-wallet -ipcconnect option to allow new wallet processes to connect to an existing node process.
And bitcoin#19461 adds a new dash-gui -ipcconnect option to allow new GUI processes to connect to an existing node process.