Documentation
¶
Overview ¶
Package level implements leveled logging on top of Go kit's log package. To use the level package, create a logger as per normal in your func main, and wrap it with level.NewFilter.
var logger log.Logger logger = log.NewLogfmtLogger(os.Stderr) logger = level.NewFilter(logger, level.AllowInfo()) // <-- logger = log.With(logger, "ts", log.DefaultTimestampUTC)
It's also possible to configure log level from a string. For instance from a flag, environment variable or configuration file.
fs := flag.NewFlagSet("myprogram")
lvl := fs.String("log", "info", "debug, info, warn, error")
var logger log.Logger
logger = log.NewLogfmtLogger(os.Stderr)
logger = level.NewFilter(logger, level.Allow(level.ParseDefault(*lvl, level.InfoValue()))) // <--
logger = log.With(logger, "ts", log.DefaultTimestampUTC)
Then, at the callsites, use one of the level.Debug, Info, Warn, or Error helper methods to emit leveled log events.
logger.Log("foo", "bar") // as normal, no level
level.Debug(logger).Log("request_id", reqID, "trace_data", trace.Get())
if value > 100 {
level.Error(logger).Log("value", value)
}
NewFilter allows precise control over what happens when a log event is emitted without a level key, or if a squelched level is used. Check the Option functions for details.
Example (Basic) ¶
package main
import (
"os"
"github.com/go-kit/log"
"github.com/go-kit/log/level"
)
func main() {
logger := log.NewLogfmtLogger(os.Stdout)
level.Debug(logger).Log("msg", "this message is at the debug level")
level.Info(logger).Log("msg", "this message is at the info level")
level.Warn(logger).Log("msg", "this message is at the warn level")
level.Error(logger).Log("msg", "this message is at the error level")
}
Output: level=debug msg="this message is at the debug level" level=info msg="this message is at the info level" level=warn msg="this message is at the warn level" level=error msg="this message is at the error level"
Example (Filtered) ¶
package main
import (
"errors"
"os"
"github.com/go-kit/log"
"github.com/go-kit/log/level"
)
func main() {
// Set up logger with level filter.
logger := log.NewLogfmtLogger(os.Stdout)
logger = level.NewFilter(logger, level.AllowInfo())
logger = log.With(logger, "caller", log.DefaultCaller)
// Use level helpers to log at different levels.
level.Error(logger).Log("err", errors.New("bad data"))
level.Info(logger).Log("event", "data saved")
level.Debug(logger).Log("next item", 17) // filtered
}
Output: level=error caller=example_test.go:33 err="bad data" level=info caller=example_test.go:34 event="data saved"
Example (Parsed) ¶
package main
import (
"errors"
"flag"
"os"
"github.com/go-kit/log"
"github.com/go-kit/log/level"
)
func main() {
fs := flag.NewFlagSet("example", flag.ExitOnError)
lvl := fs.String("log-level", "", `"debug", "info", "warn" or "error"`)
fs.Parse([]string{"-log-level", "info"})
// Set up logger with level filter.
logger := log.NewLogfmtLogger(os.Stdout)
logger = level.NewFilter(logger, level.Allow(level.ParseDefault(*lvl, level.DebugValue())))
logger = log.With(logger, "caller", log.DefaultCaller)
// Use level helpers to log at different levels.
level.Error(logger).Log("err", errors.New("bad data"))
level.Info(logger).Log("event", "data saved")
level.Debug(logger).Log("next item", 17) // filtered
}
Output: level=error caller=example_test.go:53 err="bad data" level=info caller=example_test.go:54 event="data saved"
Index ¶
- Variables
- func Debug(logger log.Logger) log.Logger
- func Error(logger log.Logger) log.Logger
- func Info(logger log.Logger) log.Logger
- func Key() interface{}
- func NewFilter(next log.Logger, options ...Option) log.Logger
- func NewInjector(next log.Logger, level Value) log.Logger
- func Warn(logger log.Logger) log.Logger
- type Option
- type Value
Examples ¶
Constants ¶
This section is empty.
Variables ¶
var ErrInvalidLevelString = errors.New("invalid level string")
ErrInvalidLevelString is returned whenever an invalid string is passed to Parse.
Functions ¶
func Key ¶
func Key() interface{}
Key returns the unique key added to log events by the loggers in this package.
func NewFilter ¶
NewFilter wraps next and implements level filtering. See the commentary on the Option functions for a detailed description of how to configure levels. If no options are provided, all leveled log events created with Debug, Info, Warn or Error helper methods are squelched and non-leveled log events are passed to next unmodified.
func NewInjector ¶
NewInjector wraps next and returns a logger that adds a Key/level pair to the beginning of log events that don't already contain a level. In effect, this gives a default level to logs without a level.
Types ¶
type Option ¶
type Option func(*logger)
Option sets a parameter for the leveled logger.
func AllowDebug ¶
func AllowDebug() Option
AllowDebug allows error, warn, info and debug level log events to pass.
func AllowInfo ¶
func AllowInfo() Option
AllowInfo allows error, warn and info level log events to pass.
func ErrNoLevel ¶
ErrNoLevel sets the error to return from Log when it squelches a log event with no level. By default, ErrNoLevel is nil; in this case the log event is squelched with no error.
func ErrNotAllowed ¶
ErrNotAllowed sets the error to return from Log when it squelches a log event disallowed by the configured Allow[Level] option. By default, ErrNotAllowed is nil; in this case the log event is squelched with no error.
func SquelchNoLevel ¶
SquelchNoLevel instructs Log to squelch log events with no level, so that they don't proceed through to the wrapped logger. If SquelchNoLevel is set to true and a log event is squelched in this way, the error value configured with ErrNoLevel is returned to the caller.
type Value ¶
type Value interface {
String() string
// contains filtered or unexported methods
}
Value is the interface that each of the canonical level values implement. It contains unexported methods that prevent types from other packages from implementing it and guaranteeing that NewFilter can distinguish the levels defined in this package from all other values.
func DebugValue ¶
func DebugValue() Value
DebugValue returns the unique value added to log events by Debug.
func ErrorValue ¶
func ErrorValue() Value
ErrorValue returns the unique value added to log events by Error.
func InfoValue ¶
func InfoValue() Value
InfoValue returns the unique value added to log events by Info.
func Parse ¶ added in v0.2.1
Parse a string to its corresponding level value. Valid strings are "debug", "info", "warn", and "error". Strings are normalized via strings.TrimSpace and strings.ToLower.
func ParseDefault ¶ added in v0.2.1
ParseDefault calls Parse and returns the default Value on error.
Source Files