Tracing Configuration

Sword can configure a global tracing subscriber to capture log events across the entire application.

Configuration is loaded from the [tracing] section in TOML.

Automatic initialization

use sword::prelude::*;

let app = Application::builder(config)
    .with_module::<UsersModule>()
    .build();

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 = []

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

Available formats

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 time-style and time-pattern.

Optional fields with with-fields

Optional log metadata is controlled with a single key: with-fields.

Supported values:

• target
• file
• line-number
• thread-id
• thread-name

Includes target and source location.

time-style

Supported values:

• system: uses tracing-subscriber default time formatter
• uptime: prints elapsed time since subscriber initialization
• local: prints local date/time using an strftime pattern
• utc: prints 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. Useful examples:

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

Sword defaults:

• local: "%Y-%m-%d %H:%M:%S"
• utc: "%Y-%m-%dT%H:%M:%SZ"

Env Filter RUST_LOG and filter

If use-env-filter = true, Sword tries to read RUST_LOG.

If RUST_LOG is missing or invalid, filter is used.

If use-env-filter = false, filter is always used.