From 165fb931ea1e70460d5ebd30fa22e3aa6ba8861d Mon Sep 17 00:00:00 2001 From: Vito Caputo Date: Fri, 17 Nov 2023 12:30:32 -0800 Subject: [PATCH] man: add note about journald forwarding being sync This footgun should at least be documented, if there's not going to be a shortcut setting to establish the async `journalctl --follow` equivalent. Fixes: https://github.com/systemd/systemd/issues/2815 --- man/journald.conf.xml | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/man/journald.conf.xml b/man/journald.conf.xml index 1c0487a4fc6..e150d04dcff 100644 --- a/man/journald.conf.xml +++ b/man/journald.conf.xml @@ -386,6 +386,15 @@ the log buffer, for example by adding log_buf_len=8M to the kernel command line. systemd will automatically disable kernel's rate-limiting applied to userspace processes (equivalent to setting printk.devkmsg=on). + + Note: Forwarding is performed synchronously within journald, and may significantly affect its + performance. This is particularly relevant when using ForwardToConsole=yes in cloud environments, + where the console is often a slow, virtual serial port. Since journald is implemented as a + conventional single-process daemon, forwarding to a completely hung console will block journald. + This can have a cascading effect resulting in any services synchronously logging to the blocked + journal also becoming blocked. Unless actively debugging/developing something, it's generally + preferable to setup a journalctl --follow style service redirected to the + console, instead of ForwardToConsole=yes, for production use. -- 2.47.3