Expand description
Logging initialization and configuration.
§Why colour is off
The layer below is built with with_ansi(false), and that is not a style
choice. The fmt layer colours its output whenever tracing-subscriber’s
ansi feature is compiled in, and that default asks nothing about what is
downstream: it does not test whether stderr is a terminal, and on Windows
it does not enable the console’s virtual-terminal mode either. Escapes
therefore reached every consumer of the logs — the file a service
definition redirects to, an agent reading the pipe, and consoles that
print them literally as ←[2m in front of every line.
Colour is switched off rather than made conditional, because the condition
cannot be answered honestly here. IsTerminal alone does not settle it on
Windows, where a console handle reports as a terminal whether or not it
will interpret an escape; answering it properly means enabling
virtual-terminal mode through the Win32 console API and falling back when
that fails — a direct platform dependency and a block of unsafe FFI,
bought for decoration on a headless gateway whose output is read by service
managers, log files and agents far more often than by a person. The one
surface an operator actually reads, the startup banner, is println! on
stdout and was never coloured.
This also holds the program’s own logs to the rule its command output already follows: piped output is escape-free, because that is what makes it usable as structured data.
tests/main_startup_e2e.rs::the_log_stream_carries_no_ansi_escapes is what
keeps this true. A record’s text is identical either way, so only a real
process writing to a real pipe can tell the two apart — no unit test in
this module can.