LogLayer for Go

Transport Configuration ​

Transports are wired into a *loglayer.LogLayer at construction time via the Config struct. This page covers the construction-time options. For runtime mutation (add, remove, replace, reach the underlying logger), see Transport Management.

Single transport ​

go
log := loglayer.New(loglayer.Config{
    Transport: structured.New(structured.Config{}),
})

Config.Transport is the typical entry point for a logger that emits to one place.

Multiple transports ​

go
log := loglayer.New(loglayer.Config{
    Transports: []loglayer.Transport{
        pretty.New(pretty.Config{}),
        structured.New(structured.Config{Writer: f}),
    },
})

Use Config.Transports (plural) to fan out to several transports at once. Setting both Transport and Transports panics with loglayer.ErrTransportAndTransports. See Multiple Transports for fan-out semantics and ordering.

BaseConfig ​

Every built-in transport embeds transport.BaseConfig, which carries three fields shared across the line-up:

FieldTypeDefaultPurpose
IDstringauto-generatedStable handle for runtime management calls (RemoveTransport(id), GetLoggerInstance(id)).
DisabledboolfalseSuppress this transport's emissions without removing it. Equivalent to calling SetEnabled(false) after construction.
Levelloglayer.LogLevelLogLevelTracePer-transport minimum level. Defaults to accepting every level; the logger's own level state is the primary filter. Set this when you want a transport to receive only entries at or above a specific level (e.g. an error-only sink in a fan-out).
go
console.New(console.Config{
    BaseConfig: transport.BaseConfig{
        ID:    "console",
        Level: loglayer.LogLevelInfo,
    },
})

Transport IDs ​

BaseConfig.ID is optional. When you omit it, the transport gets an auto-generated ID, so multiple no-ID transports never collide. Supply your own ID when you'll later need to address that specific transport: RemoveTransport(id), GetLoggerInstance(id), and AddTransport's replace-by-ID semantics all key off the string you set.

go
console.New(console.Config{
    BaseConfig: transport.BaseConfig{ID: "console"},
})

For transports you set up once and never touch (a single console renderer, a one-shot test transport), leaving ID empty is fine: the auto-generated ID still works for routing, you just won't have a stable handle for management calls.

Enabling and disabling per environment ​

When you wire several transports into one logger, the same code typically runs in dev, CI, and production but you don't want every transport active in every environment. Common patterns:

  • Local dev: pretty terminal, no shipping. You don't want CI runs or laptop runs hitting the production Datadog account.
  • CI: structured JSON to stdout (so the test runner captures it), no shipping.
  • Staging / production: structured to a file plus the network shipper (Datadog, Loki, OTel).

Two ways to wire that:

Build the slice from environment ​

The most common pattern: include or exclude each transport at construction time based on env. Cheap, explicit, no runtime mutation needed.

go
transports := []loglayer.Transport{
    pretty.New(pretty.Config{
        BaseConfig: transport.BaseConfig{ID: "pretty", Level: loglayer.LogLevelDebug},
    }),
}
if os.Getenv("APP_ENV") == "production" {
    transports = append(transports, datadog.New(datadog.Config{
        BaseConfig: transport.BaseConfig{ID: "datadog", Level: loglayer.LogLevelInfo},
        APIKey:     os.Getenv("DATADOG_API_KEY"),
    }))
}
log := loglayer.New(loglayer.Config{Transports: transports})

Construct everything, disable per env via BaseConfig.Disabled ​

If your code reads cleaner with a fixed transport list, set Disabled: true on the ones that shouldn't run in this environment. The transport is still constructed (so its config is validated) but SendToLogger is a no-op.

go
isProd := os.Getenv("APP_ENV") == "production"

log := loglayer.New(loglayer.Config{
    Transports: []loglayer.Transport{
        pretty.New(pretty.Config{
            BaseConfig: transport.BaseConfig{ID: "pretty", Disabled: isProd},
        }),
        datadog.New(datadog.Config{
            BaseConfig: transport.BaseConfig{ID: "datadog", Disabled: !isProd},
            APIKey:     os.Getenv("DATADOG_API_KEY"),
        }),
    },
})

Toggling at runtime ​

Cast the transport's exported SetEnabled(bool) method (inherited from BaseTransport) to flip without rebuilding. Useful for admin endpoints or feature-flag-driven rollouts:

go
if t, ok := tr.(interface{ SetEnabled(bool) }); ok {
    t.SetEnabled(false)
}

For routing rules beyond on/off (e.g. only ship audit.* entries to Datadog), see Groups.

See Also ​