Struct JsonFormat

pub struct JsonFormat;

JSON event formatter for structured logging with OpenTelemetry integration.

This formatter serializes tracing events into JSON format with additional OpenTelemetry metadata including trace IDs, span IDs, and span hierarchy information. It’s designed to work with the tracing-subscriber ecosystem and provides rich context for log analysis.

Features

• Structured JSON output with consistent field names
• Automatic inclusion of OpenTelemetry trace and span IDs
• Hierarchical span information for request tracing
• ISO 8601 timestamp formatting
• Proper handling of event fields and metadata

JSON Structure

The generated JSON includes the following fields:

• timestamp: ISO 8601 formatted timestamp
• level: Log level (ERROR, WARN, INFO, DEBUG, TRACE)
• target: The module path where the event was recorded
• trace_id: OpenTelemetry trace ID (if available)
• span_id: OpenTelemetry span ID (if available)
• spans: Array of parent spans with their fields
• Additional fields from the log event, including message

Trait Implementations

impl<S, N> FormatEvent<S, N> for JsonFormat

where S: Subscriber + for<'lookup> LookupSpan<'lookup>, N: for<'writer> FormatFields<'writer> + 'static,

fn format_event( &self, ctx: &FmtContext<'_, S, N>, writer: Writer<'_>, event: &Event<'_>, ) -> Result

Write a log message for Event in Context to the given Writer.