# \[PATCH v4 05/12\] simple-ipc: design documentation for new IPC mechanism - From: Jeff Hostetler via GitGitGadget \ - Date: 2021-02-17 21:50:28 - List: git - Page: https://ratatoskr.run/git/2021/02/7876791 - Thread: https://ratatoskr.run/git/2021/01/7872144/t/2.md ```text From: Jeff Hostetler Brief design documentation for new IPC mechanism allowing foreground Git client to talk with an existing daemon process at a known location using a named pipe or unix domain socket. Signed-off-by: Johannes Schindelin Signed-off-by: Jeff Hostetler --- Documentation/technical/api-simple-ipc.txt | 34 ++++++++++++++++++++++ 1 file changed, 34 insertions(+) create mode 100644 Documentation/technical/api-simple-ipc.txt diff --git a/Documentation/technical/api-simple-ipc.txt b/Documentation/technical/api-simple-ipc.txt new file mode 100644 index 000000000000..670a5c163e39 --- /dev/null +++ b/Documentation/technical/api-simple-ipc.txt @@ -0,0 +1,34 @@ +simple-ipc API +============== + +The simple-ipc API is used to send an IPC message and response between +a (presumably) foreground Git client process to a background server or +daemon process. The server process must already be running. Multiple +client processes can simultaneously communicate with the server +process. + +Communication occurs over a named pipe on Windows and a Unix domain +socket on other platforms. Clients and the server rendezvous at a +previously agreed-to application-specific pathname (which is outside +the scope of this design). + +This IPC mechanism differs from the existing `sub-process.c` model +(Documentation/technical/long-running-process-protocol.txt) and used +by applications like Git-LFS. In the simple-ipc model the server is +assumed to be a very long-running system service. In contrast, in the +LFS-style sub-process model the helper is started with the foreground +process and exits when the foreground process terminates. + +How the simple-ipc server is started is also outside the scope of the +IPC mechanism. For example, the server might be started during +maintenance operations. + +The IPC protocol consists of a single request message from the client and +an optional request message from the server. For simplicity, pkt-line +routines are used to hide chunking and buffering concerns. Each side +terminates their message with a flush packet. +(Documentation/technical/protocol-common.txt) + +The actual format of the client and server messages is application +specific. The IPC layer transmits and receives an opaque buffer without +any concern for the content within. -- gitgitgadget ```