Tracing Configuration

Sword can configure a global tracing subscriber to capture traces across the entire application. It is configured from the [tracing] section of the TOML file. This subscriber is initialized automatically while the application is being built.

Supported fields

Key	Type	Default	Description
enabled	bool	true	Enables or disables global subscriber initialization
use-env-filter	bool	true	Tries to read directives from RUST_LOG before using filter
filter	String	"info"	Fallback filter when RUST_LOG is missing or disabled
format	full | pretty | compact | dev | json	full	Subscriber output format
time-style	system | uptime | local | utc | none	system	Timestamp source and style
time-pattern	String?	None	strftime pattern used by local and utc
with-fields	target[] | file[] | line-number[] | thread-id[] | thread-name[]	["target"]	Optional metadata included on each event

Complete example

[tracing]
enabled = true
use-env-filter = true
filter = "info,sword=info,sqlx=warn"

format = "dev"
time-style = "utc"
time-pattern = "%H:%M:%S"

with-fields = []

Output format

The format is chosen with the format key.

full format

Uses the default formatter from tracing-subscriber. This is the default format and prioritizes richer metadata.

pretty format

Uses the multi-line formatter from tracing-subscriber.

Useful in development when you want clearer event blocks, although it takes more vertical space.

compact format

Uses a denser single-line format, close to the classic tracing-subscriber style.

dev format

Sword's own format for development in the terminal.

Example:

INFO  Initialized tracing subscriber
       format: Dev
       filter: info,sword=info
       use_env_filter: true

json format

Uses the native JSON formatter from tracing-subscriber, flattening event fields at the root level.

This is a solid base for log aggregation and simple observability pipelines.

Time configuration

Timestamps are controlled by two keys: time-style (time source) and time-pattern (format pattern).

Time style

Values accepted by time-style:

Value	Description
system	tracing-subscriber default time formatter
uptime	Elapsed time since subscriber initialization
local	Local date/time using an strftime pattern
utc	UTC date/time using an strftime pattern
none	Does not print timestamps

Time pattern

time-pattern only applies to local and utc. Sword uses strftime syntax, just like chrono; some examples:

Pattern	Approximate output
"%H:%M:%S"	14:32:11
"%Y-%m-%d %H:%M:%S"	2026-04-02 14:32:11	(Default local)
"%Y-%m-%dT%H:%M:%S"	2026-04-02T14:32:11
"%Y-%m-%dT%H:%M:%SZ"	2026-04-02T17:32:11Z	(Default utc)

Event filters

Sword combines two filtering sources: RUST_LOG (environment directives) and filter (TOML filter).

With use-env-filter = true, Sword tries to read RUST_LOG and uses filter only when it is missing or invalid. With use-env-filter = false, Sword always uses filter.