srog

srog is a structured logging library for Go that speaks Serilog's message-template language on top of zerolog. You write a message once — named holes in the template become typed structured fields, and a human-readable line is rendered alongside them.

Why message templates

Traditional loggers force a choice: fmt-style messages that are pleasant to read but opaque to machines, or key-value APIs that are queryable but verbose to write. Message templates give you both from a single call:

log.Information("trip {TripId} assigned to driver {DriverId} eta {EtaSeconds}s", "T-58201", "D-107", 240)

• {TripId}, {DriverId} and {EtaSeconds} become typed JSON fields ("TripId":"T-58201", "EtaSeconds":240).
• The rendered message trip T-58201 assigned to driver D-107 eta 240s is emitted for humans.
• The raw template is preserved in the @mt field, so log pipelines can group events by their template identity — exactly like Serilog.

Features

• Serilog message templates — named holes {Name}, destructuring {@obj}, stringify {$obj}, alignment, format specifiers, positional holes. Parsed templates are cached, so each template string is parsed once per process.
• Multi-sink fan-out — pretty console output and rotated JSON files at once, each sink with its own format and minimum level.
• Four output formats — human console, NDJSON, Elastic Common Schema (ECS), and OpenTelemetry OTLP/JSON log records.
• Log rotation — by size and/or time (hourly/daily), with backup and age retention plus gzip compression.
• Request-scoped logging — propagate an enriched logger through context.Context; pluggable context extractors add correlation fields such as OpenTelemetry trace_id/span_id.
• Declarative configuration — build the same logger from a JSON (or YAML) config file, with pluggable sink types registered by integration modules.
• Async sinks — offload slow destinations to a background goroutine with a bounded, non-blocking queue.
• Integrations — net/http middleware, gRPC interceptors, Echo middleware, a direct Elasticsearch sink, and OpenTelemetry both ways: trace-correlation fields and direct log export to the Collector over OTLP.
• Fast — zerolog's zero-allocation event model underneath; the structured-only hot path allocates nothing (see Performance).

Installation

go get github.com/dvislobokov/srog

Integration subpackages with heavier dependencies live in their own Go modules and are fetched separately, for example:

go get github.com/dvislobokov/srog/sroggrpc
go get github.com/dvislobokov/srog/srogecho
go get github.com/dvislobokov/srog/srogelastic
go get github.com/dvislobokov/srog/srogotel

The sroghttp middleware ships inside the main module (standard library only).

A minimal example

package main

import (
	"errors"

	"github.com/dvislobokov/srog"
)

func main() {
	log := srog.MustNew(
		srog.WithConsole(srog.NoColor()),
		srog.WithLevel(srog.DebugLevel),
	)
	defer log.Close()

	log.Debug("evaluating {Candidates} drivers near {Zone}", 14, "downtown-east")
	log.Information("trip {TripId} assigned to driver {DriverId} eta {EtaSeconds}s", "T-58201", "D-107", 240)
	log.Warning("surge multiplier {Multiplier} exceeds cap in {Zone}", 3.1, "airport")
	log.Error(errors.New("driver socket closed"), "lost contact with driver {DriverId}", "D-107")
}

Real captured output:

2026-07-13T11:55:30+03:00 DBG evaluating 14 drivers near downtown-east
2026-07-13T11:55:30+03:00 INF trip T-58201 assigned to driver D-107 eta 240s
2026-07-13T11:55:30+03:00 WRN surge multiplier 3.1 exceeds cap in airport
2026-07-13T11:55:30+03:00 ERR lost contact with driver D-107 driver socket closed

Swap the console sink for the default JSON sink and the same calls produce structured NDJSON:

{"level":"info","@mt":"trip {TripId} assigned to driver {DriverId} eta {EtaSeconds}s","TripId":"T-58201","DriverId":"D-107","EtaSeconds":240,"time":"2026-07-13T11:55:30+03:00","message":"trip T-58201 assigned to driver D-107 eta 240s"}

TIP

Every example in this documentation is a compiled, executed Go program; all shown output is captured from real runs.

Documentation map

Page	Contents
Quick Start	Construct a logger, log at each level, console vs JSON
Message Templates	Full template syntax reference
Levels	Severity ladder, filtering, per-sink levels
Enrichment	ForContext, Named, stack traces, caller info
Sinks	Console, file, writer sinks; fan-out; async mode
Rotation	Size/time rotation, retention, compression
Configuration	JSON config file schema
Context	Request-scoped logging and propagation
Integrations	HTTP, gRPC, Echo, Elasticsearch, OpenTelemetry
Performance	Benchmarks and hot-path design
API Reference	Every exported symbol

Source: github.com/dvislobokov/srog